ALBERT

Notizen: Summary The crustacean class Mystacocarida is restricted to the interstitial marine sand environment. A cinemicrographic analysis of the functional morphology of locomotion in the mystacocarid D. typica was undertaken to demonstrate how this species progresses through the interstitial spaces. Locomotion is completely dependent on the presence of dorsal and ventral substrates. The biramous second antennae and mandibles are the force-generating appendages. During a locomotory cycle, the exopods of the second antennae and mandibles are directed dorsolaterally against a dorsal substrate. This creates a downward force enabling the endopods to gain purchase on the ventral substrate. The second antennae and mandibles undergo coordinated cyclic movements. Each cycle results in two power and two recovery strokes. The animals undergo approximately 4 complete cycles per second. The calculated maximum rate of locomotion is 420 μm/s. The measured rate under test conditions is 250 μm/s. A turning-escape reaction in response to air bubbles and other factors results in a 180° turn in a confined space within 1.5 s. These data are discussed in relation to the morphological conservatism of mystacocarids, their presumed neotenic origin and their observed migration over a tidal cycle. It is proposed that all crawling interstitial animals will have developed specific mechanisms to increase frictional forces between their locomotory appendages and the surrounding substrate.

Notizen: Summary The fine structure of the ocellus of Sarsia tubulosa is described. The ocellar cup is formed of pigment cells and receptor cells. The receptor cells outnumber the pigment cells in almost a 2:1 ratio. Lateral extensions of neighbouring pigment cells enclose a distal region of 2 to 10 receptor cells. The receptor cell body is 5–7 μm in diameter with an apical extension (20–60 μm long) that reaches the ocellar cavity. A cilium (9+2 microtubules) arises from the distal part of the receptor cell. The ciliary membrane forms lateral microvilli. The tips of a number of cilia are swollen into large vesicles forming a “cornea”. The central region of the ocellar cavity contains extracellular electron dense homogeneous material surrounded by swollen ciliary tips and small vesicles. The close apposition between the plasma membrane covering the distal part of adjacent receptor cells as well as the adjacent ciliary shafts suggests the presence of gap junctions. The basal part of each receptor cell forms an axon. The axons of receptor cells form 3 to 4 nerve bundles that join to form the optic nerve. Synapses occur between receptor cell bodies, between axons and receptor cell bodies and among axons.

Notizen: Summary In Rhapidostreptus virgator exocrine gland complexes are found in the anal valves of both sexes. Every gland complex consists of about 200 secretory units, each of which is comprised of four cells: two secretory cells, an intermediary cell, and a canal cell. The amount of secretion produced by these glands varies during the intermoult cycle: it is very small in freshly moulted individuals (postmoult phase), at a medial level during the following intermoult phase, and very large in the premoult phase. The secretion may be used to form the excrement clumps and above all to build the moulting chamber.

Notizen: Summary The skin vascularization was investigated troughout the ontogenetic development and in adults of two anurans, Rana temporaria and Bufo bufo, and two urodeles, Triturus vulgaris and Triturus cristatus. It was found that, contrary to the urodele larvae, the anuran tadpoles have a very sparse skin vascularization. During the early stages of anuran metamorphosis the skin capillary network becomes dense; later, during skin metamorphosis, a second, venous, network is formed as anastomoses between the subcutaneous vein ramifications. In the urodeles, metamorphosis is not accompanied by any significant morphological changes in the skin vascularization, and a subcutaneous network is not formed. It is suggested that the reduced skin vascularization in anuran tadpoles is an advanced larval character relative to the rich vascularization of the skin in urodele larvae. It is further suggested that anuran tadpoles have a reduced ability to utilize gaseous exchange through the skin. The function of the subcutaneous venous network found in anurans after metamorphosis is obscure; experiments indicate a vasomotor regulation which is neither adrenergic nor cholinergic.

Notizen: Summary The larval morphology of the marine bryozoan Bowerbankia gracilis has been investigated by light and electron microscopy. The barrel-shaped larva (200 μm long and 150 μm in diameter) is light yellow without any apparent eyespots, although it is positively phototactic during its brief free-swimming existence. The primary morphological characteristics of the larva are: (1) a large corona that forms most of the larval surface, (2) a small apical disc without blastemas, (3) a deep pallial sinus lined by an extensive pallial epithelium, (4) an internal sac without regional specializations, and (5) a polypide rudiment in the oral hemisphere. This organization is characteristic of larvae of the ctenostome superfamily Vesicularioidea, and differs radically from the organization of all other bryozoan larvae examined. The major morphological differences occur in the size and organization of the apical disc, the pallial epithelium, and the internal sac. In most bryozoans, these regions of the larval epithelium represent rudiments of the polypide and the body wall epidermis of the ancestrula. The oral polypide rudiment, the extensive pallial epithelium, and the reduced internal sac in vesicularioid larvae indicate that their pattern of metamorphosis also differs radically from the metamorphoses of other bryozoans.

Notizen: Summary A sponge (Ephydatia fluviatilis L.) embedded in styrol methacrylate was cut into pieces with a fretsaw. One piece was then soaked in xylene to remove the polymer, dried in the critical-point dryer, gold-coated and finally examined in the scanning electron microscope. The pictures obtained reveal the three dimensional arrangement of the cells in the sponge, through the openings in the cut surface.

Notizen: Summary The organization of the female genital apparatus of the bdelloid rotifer Philodina roseola was analyzed by light and electron microscopy. It differs from that of the monogononts in several respects: the gonad is paired; in each gonad, the follicular layer completely surrounds the syncytial vitellarium and the cluster of ovocytes; the cytoplasmic bridges between the vitellarium and the immature ovocytes exist but are much narrower; a specialized junction (5–8 nm intercellular space) is established between the follicular layer and the whole area of the germo-vitellarium complex. Preliminary observations about the movements of organelles during ovogenesis were made at an ultrastructural level.

Notizen: Summary An ultrastructural study of the tentacles of Themiste lageniformis (Sipuncula) was conducted as part of a larger study of head metamorphosis in the species. The oral surface of the tentacles is constructed of a multiciliated, pseudostratified, columnar epithelium while the aboral surface is an unciliated, cuboidal epithelium. Intraepidermal mucous cells lie near the junction of the oral and aboral regions. The basal portion of the epidermal cells is embedded in a thick, collagenous extracellular matrix which contains outer circular muscles, inner longitudinal muscles, the main tentacular nerve and its branches. Three tentacular canals are present and are lined by peritoneum. Hemerythrocytes and coelomocytes flow through the lumen of the canals in a regular pattern. Justification for the designation of the tentacular canals as coelomic rather than vascular is discussed.

Notizen: Summary The coxal organs of different Geophilomorpha were studied by scanning and by transmission electron microscopy. 1) The coxae of the last trunk-segment contain pores in different arrangements and numbers. They are the openings of the coxal organs. 2) The coxal organs are formed by four different cell types: the main epithelium consists of radially arranged transporting cells, surrounded by junctional cells, gland cells, and the cells of the pore channel. 3) The cells of the transporting epithelium show an enlargement of the apical and basal surface. Deep and narrow extracellular channels of the apical infoldings are closely associated by mitochondria (plasmalemma-mitochondrial complexes). The epithelium is covered by a prominent cuticle with a spacious subcuticle. 4) A distinct mucous layer covers the cuticle of the transporting epithelia, and is secreted by the gland cells. 5) A small cellular sheath separates the epithelium of the coxal organ against the haemolymph. 6) The possible function of the coxal organs in ion and fluid transport is discussed.

Notizen: Summary Each pigment-cup eye of Polycystis naegelii consists of two retinal clubs and a single pigmented cell. The latter is divided into two cavities by a septum. Under bright illumination the photoreceptor process appears as a disk containing membranous laminar whorls; under faint illumination the latter are replaced by numerous straight, closely packed, microvilli. This morphological variation is correlated with the intensity of the photoreceptor's exposure to light. The lenticular structures described by previous light microscopists have not been observed.

Notizen: Summary The microstructure of the surface of thirteen marine littoral and two terrestrial isopods was investigated by scanning electron microscopy. A great diversity of surface ornamentation is present, including non-sensory microscales, pits, tubercles, and ridges, and sensory tricorns, pit organs, pores, papillae and setae. Microscales are common features of the integument surface; their shape and size are highly variable. Tricorns were not observed on the marine littoral isopods. Several hitherto undescribed structures were observed including spade-like projections from the tergite surface of Oniscus asellus, hair-like filaments associated with the microscales of Jaera and ridged conical protuberances on Edotea triloba and E. montosa. The possible function of certain surface microstructures is discussed.

Notizen: Summary Two cells which lie at the left and at the right near the anterior end of Cirrifera aculeata (Ax, 1951) (Proseriata) are interpreted as presumed photoreceptors. In the left cell up to 70 slightly modified cilia extend into a large intracellular cavity. Besides these cilia microvilli and electron-dense granules are present. The presumed light sensitive structures of the right cell are formed by tubular vacuoles which are arranged without gaps, thus comparable to the microvilli of a rhabdom. The functional and evolutionary aspects of these two cell types are discussed.

Notizen: Summary The settlement and metamorphosis of the marine bryozoan Bowerbankia gracilis has been examined by light and electron microscopy. The period of rapid morphogenesis consists of the following sequence of morphogenetic movements: 1) eversion of the internal sac, 2) retraction of the apical disc, 3) coronal involution and exposure of the pallial epithelium, and 4) closure of the internal coronal cavity. The eversion of the internal sac at the onset of metamorphosis coincides with a sudden reversal of the direction of beat of the coronal cilia. The reversed beating of the coronal cilia wafts the adhesive secreted by the internal sac over the metamorphosing larva, forming the pellicle. The internal sac is subsequently internalized and histolyzed with the corona and the other transitory larval tissues, and the extensive pallial epithelium forms the epidermis of the ancestrular body wall (cystid). Type I mesenchyme cells form an incomplete somatic mesothelium beneath the differentiating cystid epidermis, and Type II mesenchyme cells become mobile phagocytes. The main body cavity develops by the histolytic enlargement of the internal cavity formed during coronal involution. The apical disc degenerates and the polypide develops from rudiments in the oral hemisphere of the larva. The distinctive larval morphology and metamorphosis of vesicularioid ctenostomes are compared with other bryozoans, and possible evolutionary trends are considered.

Notizen: Summary Ultrastructural study of the buccal tentacles of Holothuria forskali revealed that each tentacle bears numerous apical papillae. Each papilla consists of several differentiated sensory buds. The epidermis of the buds is composed of three cell types, i.e. mucus cells, ciliated cells, and glandular vesicular cells (GV cells). The GV cells have apical microvilli; they contain bundles of cross striated fibrillae associated with microtubules. Ciliated cells have a short non-motile cilium. Bud epidermal cells intimately contact an epineural nervous plate which is located slightly above the basement membrane of the epidermis. The epineural plate of each bud connects with the hyponeural nerve plexus of the tentacle. This nerve plexus consists of an axonic meshwork surrounded in places by sheath cells. The buccal tentacles have well-developed mesothelial muscles. Direct innervation of these muscles by the hyponeural nerve plexus was not seen. It is suggested that the buccal tentacles of H. forskali are sensory organs. They would recognize the organically richest areas of the sediment surface through the chemosensitive abilities of their apical buds. Tentacles presumably trap particles by wedging them between their buds and papillae.

Notizen: Summary Only one non-ciliary proprioceptor is developed on the mandible of Thrips. It consists of two bipolar, multiterminal sense cells, the dendrites of which form a strand extended between the tentorium and the back mandibular margin. The dendritic terminals are embedded in an electron-dense, homogeneous matrix, which obviously represents the stimulus transmitting structure. The strand is stretched, if the mandible is moved forwards and upwards. In Thrips, the system of proprioceptors monitoring the mandibular movement is reduced extensively compared with other pterygote insects. This is linked up with the far-reaching reduction of the mobility of the mandible itself.

Notizen: Summary The nephridia of Ophryotrocha puerilis are segmental organs. The nephrostome opens at the posterior margin of a setigerous segment into the coelomic cavity of this segment. The nephridial canal is made up of about 15 cells. These cells form an S-shaped tubule which extends into the following segment. The lumen of the nephridial canal ranges from 2 to 7 μm in diameter. The nephropore opens laterally on the ventral surface of the body wall. In cross sections, one, two, or three cells are seen forming the canal. The inner surfaces of the canal cells are of different appearances along the canal. Since no regular pattern of cell distribution was found along the canals of different nephridia it is assumed that changes in cell structure along the canal are due to functional states or properties rather than to anatomically fixed regional differences. The canal cells either show smooth contours or they form brush borders of microvilli or sponge-like inner surfaces with a system of vacuolar canals running through the cytoplasm. Most of the canal cells are filled with various kinds of vesicles. Usually two or three cells contain larger vesicles up to 2.5 μm in diameter with more or less electron-dense contents. Some of these vesicles resemble lysosomes. There are at least three bundles of cilia in each canal. In young specimens the number of cilia in one bundle is smaller (10–15) than in adult specimens (60–70). The nephridia do not show sex specific differences. The female nephridia do not function as genital ducts. As judged from the sizes of sperm and nephridia it appears to be possible that sperm are shed via male nephridia.

Notizen: Summary Spermiogenesis of the architectonicid Philippia (Psilaxis) oxytropis was studied using transmission electron microscopy. Both spermatids and mature sperm of Philippia show features comparable to sperm/spermatids of euthyneuran gastropods (opisthobranchs, pulmonates) and not mesogastropods (with which the Architectonicidae are commonly grouped). These features include: (1) Accumulation of dense material on the outer membrane of anterior of the early spermatid nucleus — this material probably incorporated into the acrosome; (2) Structure of the unattached and attached spermatid acrosome (apical vesicle, acrosomal pedestal) accompanied by curved (transient) support structures; (3) Formation of the midpiece by individual mitochondrial wrapping around the axonemal complex, and the subsequent fusion and metamorphosis of the mitochondria to form the midpiece; (4) Presence of periodically banded coarse fibres surrounding the axonemal doublets and intra-axonemal rows of granules. A glycogen piece occurs posterior to the midpiece but is a feature observed in both euspermatozoa of mesogastropods (and neogastropods) and in sperm of some euthyneurans. Despite the lack of paracrystalline material or glycogen helices within the midpiece (both usually associated with sperm of euthyneurans), the features of spermiogenesis and sperm listed indicate that the Architectonicidae may be more appropriately referable to the Euthyneura than the Prosobranchia.

Notizen: Summary The exopodal branches of the pleopods of Cyathura carinata have a thicker cuticle than the endopodites, but the hypodermis proved to be very thin and probably of respiratory function. The nuclei are found in ‘pilaster areas’ together with stabilizing elements (micro-tubuli attached to cuticular pegs), which are typical for hypodermal ‘tendon cells’ of other arthropods. Precipitation of Ag2S revealed that the cuticle of the exopod is more permeable to silver ions than the cuticle of the endopods. The endopodal epithelia have the features of typical osmoregulating tissues (apical folds, mitochondrial pumps, and basal invaginations of the plasma membrane) and reduce silver nitrate. The stabilizing ‘pilaster areas’ are composed of the same elements as in the exopods.

Notizen: Summary The eyes of Rostanga pulchra larvae develop immediately behind the velar lobes approximately 20 days after hatching. Each is a pigmented cup with a lens occupying the concavity of the cup. The eye is composed of a single corneal cell, 7 sensory cells and 8 pigment cells. Sensory cells are of the rhabdomeric type and bear microvilli as their receptive surface. The eye connects to the inner dorsal region of the optic ganglion through a nerve that consists of axons arising from the 7 sensory cells. The optic ganglion, in turn, joins the lateral region of the cerebral ganglion. The possible functions of the eye are discussed in relation to larval behavior.

Notizen: Summary The small cells of the midgut glands of Armadillidium vulgare, Oniscus asellus, Porcellio scaber, and Alloniscus oahuensis were examined by transmission electron microscopy, X-ray microanalysis, histochemistry, and atomic absorption spectroscopy. Inclusions containing large amounts of heavy metals were the most prominent feature of these cells. Various areas of the midgut glands exhibited large differences in storage capacity. Juveniles were free of lead.

Notizen: Summary The oesophageal epithelium of eleven sea-water and four fresh-water teleosts was studied by light and electron microscopy. In sea-water species, the three main regions from pharynx to stomach are: a thick stratified pharyngeal epithelium with complex foldings and numerous mucous cells, and a simple microvillous columnar epithelium in the middle and posterior part. In fresh-water species, foldings are simple, the first two regions occupy the whole length, and no microvillous epithelium is observed. The adaptation from fresh-water to sea-water is characterized by the development of the third, microvillous epithelium. Different microridge cells appear in the mucous region of fresh-water and sea-water Anguilla anguilla oesophagus. The ultrastructure of the microvillous epithelium suggests an active transport of ions along the lateral membranes with water recycling in frequently dilated intercellular spaces.

Notizen: Summary The cricket Cycloptiloides canariensis (Gryllidae, Mogoplistinae) has compound eyes of the eucone apposition type. They consist of relatively few (about 160–190) ommatidia with a wide angle of divergence. Each ommatidium has two primary pigment cells, four Semper cells and eight retinula cells whose four distal rhabdomeres are arranged around the tip of the crystalline cone. The screening pigments are contained mainly in the primary pigment and retinula cells, while the secondary pigment cells are sparsely pigmented. The dorsal eye region can be distinguished by the following characteristics: lack of dioptric apparatus (flat, unfacetted cornea, absence of cones), densely packed rhabdomes in approximately parallel orientation extending distally to the cornea and possessing a markedly increased cross-sectional area in comparison with those of normal ommatidia. Screening pigments are absent. The importance of this dorsal region will be discussed.

Notizen: Summary The pore plates of Pimpla are about 40–75 μm long and 5–7 μm wide. Through a central cuticular canal they are in contact with the lumen of the antennae. Under the perforated plate blind-ending tunnels extend in the distal and proximal directions. It is extremely probable, that the pore plates of Hymenoptera are derivatives of basiconical sensilla. The ontogeny of the pore plates was followed back to the beginning of the deposition of the cuticulin layer. Each pore plate ‘anlage’ contains 40–47 sensory cells and 6 enveloping cells. Envelope cell 1 secretes the dendritic sheath, which is fully reduced during ontogeny. The envelope cells 2a and b (trichogen cells) are mirror images of each other, they form the perforated plate and the pore tubules. On both sides of the trichogen cells lie the envelope cells 3a and b (tormogen cells), they also form mirror images of each other. The tormogen cells secrete a cuticular ledge, that surrounds the perforated plate. In the outer distal position lies envelope cell 4, which encircles the pore plate ‘anlage’ in the proximal direction. Envelope cell 4 folds in and retreats from the epithelium surface, thus forming a ‘joint-furrow’ around the pore plate ‘anlage’. The doubling of the trichogen cell is unusual in insects and so far has been observed in basiconic sensilla and pore plates of Hymenoptera only. The doubling of the tormogen cell until now could be established only in basiconic sensilla of Cephus and of Xiphydria (Hymenoptera, Symphyta). In pupae 3–4 days old the trichogen and tormogen cells begin to retreat from the perforated plate. In the imago this outer receptor lymph cavity is nearly completely filled by the branched outer dendritic segments.

Notizen: Summary During each moult the anal glands in Rhapidostreptus virgator are partly dissolved and subsequently rebuilt and enlarged by embryonic cells within the anal sac epithelium. An embryonic cell undergoes two mitoses thus producing the four cells which are present in a glandular unit. During the genesis of the glandular units each of the latter secretory cells produce a ciliary process, which is believed to serve as a mould for the canal cell, which in turn secretes the cuticular efferent duct.

Notizen: Summary The fertilized egg of the freshwater bryozoan Plumatella fungosa develops into an elongated ovoid larva, which after embryogenesis in the embryo sack is released into the surrounding water. During the short free-swimming stage the larva is characterized by the presence of several locomotive and attachment cell types. The ectodermal epithelial cells are provided with numerous cilia. The cytoplasm of the epithelial cells contains numerous mitochondria, Golgi bodies, and ribosomes. Gland cells containing vacuoles of flocculent, lightly staining secretion material were observed between the epithelial cells in the anterior pole of the larva. From a neural center beneath the epidermal cells in the anterior pole nerves emerge in a radial direction. These nerves may include up to 30 axons. Beneath the nerves are a lamella of collagenous fibers and a layer of muscle cells. Internally the larva possesses a coelomic cavity bounded by a squamous epithelium. At the anterior pole large, irregular cells rich in rough endoplasmic reticulum and lipid droplets are seen associated with the coelomic wall. It is concluded that the P. fungosa larva is a true planctonic larva, although highly modified and reduced. There is an acceleration of adult features with differentiation of functional zooids within the larval body. This acceleration may be an adaptation to life in freshwater.

Notizen: Summary Origin and formation of the body wall epidermis of the ancestrula in three species of gymnolaemate bryozoans were analyzed by scanning and transmission electron microscopy. In the ctenostome Bowerbankia gracilis, the aboral pallial epithelium forms the entire cystid epidermis, whereas in the anascan cheilostome Bugula neritina, the wall and roof regions of the internal sac form the epidermis. In the ascophoran cheilostome Watersipora culcullata, however, both the pallial epithelium and internal sac contribute to the body wall epidermis. In spite of these different origins, the tissues involved in production of the exoskeleton share a common ultrastructure. The various patterns of metamorphosis described here indicate that ancestrular body wall origin may be an important character in the analysis of phylogenetic relationships within the Bryozoa.

Notizen: Summary The three anterior adhesive papillae of Diplosoma macdonaldi serve to attach the larva to the substratum at settlement. Each is a cup-shaped, epidermal organ with a bulbous axial protrusion. Approximately 50 sensory neurons (anchor cells) are distributed around the rim of each papillar cup within the epithelium. An axon from each passes within the wall of the cup to the base of the papilla and thence in the hemocoel to the visceral ganglion. Microvilli arising from anchor cells form a network below the outer cuticle of the tunic. Ten to 15 sensory neurons of a second type (basal cells) are situated within the epithelium around the base of each papilla. A single cilium arises from an invagination in the soma of each basal cell and extends either proximally or distally along the surface of the epithelium. An axon from each basal cell joins the anchor cell axons to project to the visceral ganglion. We infer that papillar sensory cells allow a larva to sample the characteristics of the substrate at potential sites for settlement and metamorphosis.

Notizen: Summary Each sessile eye comprises about 60 ommatidia with large lenses (diameter 100–150 μm), spherical crystalline cones, and hypertrophied rhabdoms (diameter about 100 μm). The cones are formed by two main cone cells, and in addition two accessory cone cells are present. Seven retinula cells contribute to the rhabdom, which is fused distally and open proximally (separated rhabdomeres). A special cell type, previously designated ‘hyaline cells’ are shown to be reflecting pigment cells. These cells form a well-developed tapetal layer. Distal pigment cells screen neighbouring ommatidia. Further, the eye is delimited by two membranes homologous to the fenestrated and eye capsule membranes present in several other isopod groups. The hypertrophied rhabdoms and the elaborate tapetal layer separate the morphology of the Cirolana eye from that of other isopod eyes. These structural features makes the Cirolana eye a case of convergent development with several other deep water living crustaceans.

Notizen: Summary The lateral retinae of some advanced salticid spiders are found to conform to the ultrastructural descriptions of Eakin and Brandenburger (1971). Retinae of two forms supposed by taxonomists to be primitive, Portia and Lyssomanes, are described for the first time. Portia exhibits the overall relationships between pigmented and non-pigmented glial processes and receptors typical of advanced forms, but (i) non-pigmented processes are elaborately and irregularly divided and do not contain microtubules; (ii) four pigmented processes enclose the complex of receptor+non pigmented glial processes instead of six. The rhabdomeral layer of the retina of Lyssomanes is not invaded by processes of the pigmented glia, which forms a pigmented screen proximal to the receptive segments. The receptors are separated from each other by thin lamellae of non-pigmented glia whose somata lie in the normal position amongst those of the receptors. The retinal organisation resembles that of some nocturnal spiders such as Menneus (Blest et al. 1980). The posterior median retinae of Portia are identical in construction to those of the other accessory eyes, although smaller. Those of Lyssomanes and advanced salticids are vestigial. Shedding of photoreceptor membrane during turnover appears to be largely intracellular in all these forms, in contrast to Plexippus in which an extracellular route has been described.

Notizen: Summary The terminal organ, a structure enabling pelagosphera larvae of Sipuncula to form temporary attachments to substrata, was examined behaviorally and with light and electron microscopy for larvae of Golfingia misakiana, collected from the Florida Current. The terminal organ appears as a retractile rounded knob with a short neck joining the posterior extremity of the trunk. It can attach larvae directly to substratum or can secrete a tether-like mucus strand about which the organism moves. In unattached larvae, the terminal organ is often placed in the mouth. The terminal organ of a 5.5 day old larva consists of 29 cells: 8 epidermal, 3 mucus, 2 tension-bearing, 5 sensory, 10 retractor muscles and 1 unknown cell. The mucus cells are presumed to release the adhesive material while the microvilli on the tension-bearing cells, with their dense cores of microfilaments, bear the strain. The latter are joined directly to the retractor muscles which originate on the dorsal body wall near the anus. Two of the sensory cells terminate within the cuticle flanking the adhesive pore and are assumed to be cuticle strain receptors. Three sensory cells terminate in cilia that extend posteriorly from the pore. These may function in substratum evaluation prior to temporary attachment, or settlement preceding metamorphosis. The terminal organ is compared to adhesive organs in other soft-bodied metazoans and although it approximates the structure found in some rotifers, it is considered to be independently evolved within the Sipuncula. The terminal organ can be understood as an adaptation in young larvae for protective attachment and facilitation of feeding whereas, in older larvae, it may only function in substrate evaluation prior to settlement.

Notizen: Summary Crinoid tube feet occur in groups of three (podial triplets) that behave as functionally integrated units for food particle collection. Scanning electron microscopy shows that each triplet member has a distinctive morphology related to its behavioural role in feeding. Particularly conspicuous features are papillar distribution, papillar processes, ciliary tracts, and pores that are the openings of mucous glands. The primary podia serve for initial particle capture. The secondaries, together with lappets, play a major role in particle transfer from the primaries and may themselves also entrap particles. The tertiaries manipulate particles within the food groove after their transfer from the other podia. The tertiary podia use their papilla-free medial faces to compact mucusbound particles into boluses. In pinnules, boluses are transferred to the food groove midline by tertiaries, then propelled orally by paddling actions of these podia. Boluses are also transported by the medial ciliary tracts of the pinnules and arms. Bolus transport by tertiary paddling is probably more effective in the pinnular than the arm food groove. Short lateral ciliary tracts at the base of each primary podium may guide boluses into the main ciliary stream or may be cleansing currents. As the ultimate site of food particle collection, compaction and transfer, podial triplets represent a third adaptive level of an intricate suspension feeding system in which the first (arm postures) and second (pinnule orientations) adaptive levels are related to increasing collecting efficiency in diverse ambient flow.

Notizen: Summary The accessory eye of an African giant snail, Achatina fulica, is situated under an extension of the cornea of the main eye and invariably possesses a small lens. The accessory retina is composed of type I and type II sensory cells and nonpigmented supportive cells that closely resemble corneal cells. Type I cells contain photic vesicles, and their microvilli are comparable in length and density to those of the main retina. Type II cells bear stubby microvilli and various vesicles, but no photic vesicles. The ratio of type I to type II cells is about two to one in both accessory and main retinas. Certain electron-opaque cells scattered among corneal cells possess numerous photic vesicles and twisted microvilli that are confined to intercellular spaces. The cavity of the accessory eye, being separated from that of the main eye by two boundary layers, is filled with debris, such as granules, vesicles, and whorls.

Notizen: Summary The long and slender spines of Diadema are highly flexible, although their skeleton consists mainly of CaCO3 and behaves optically like a single monocrystal of calcite. The flexibility is due to the shape of the spine skeleton as well as to the material properties of the echinoderm calcite. The spine skeletons are hollow beams consisting of radial wedges or septs. The shape of the septs shows a broad base situated at the periphery of the cross section, producing a high load-bearing capacity with minimum weight. Furthermore, material is concentrated at the base of the spine in such a way that the strain of the structure is kept constant along the axis. The septs are connected with one another by a few transverse bars positioned as closely as possible to the axis. The load-bearing parts of the septs are free. They have small diameters similar to flexible glass fibres. The stiff spines of other echinoids are also mainly built by radial wedges, but the spaces in between are closely filled with transverse bars. On the surface of stiff spines there are low grooves between the septs. The echinoid spines are covered with an epithelium which shows a basiepithelial nerve plexus. In the stiff spines this plexus forms cords which lie protected within the superficial grooves mentioned. In the flexible spines of Diadema the cords are deeply sunken in the spaces between the septs. In this manner the nerve cords are largely free from the tensile stresses to which the spine's surface is exposed. The flexible spines were used to determine the material properties of echinoderm calcite. Young's modulus was determined for fresh (live) spines, dry spines, and cleaned spine skeletons. Fresh spines show the highest elasticity, and their Young's modulus is significantly below the Young's modulus of the other test groups. The echinoderm calcite does not show the cleavage planes of mineral calcite, and probably this feature contributes to the high flexibility of echinoderm calcite.

Notizen: Summary Heat stressed pigeons dissipate heat by panting and gular flutter which is associated with upper esophageal pulsation; these activities depend on evaporative cooling and convection from mucosal surfaces. The collar plexus, an unusual subcutaneous system of erectile veins, is the specialized vascular apparatus that seems to serve as the heat exchanger for gular flutter and upper esophageal pulsation. The collar plexus lies between the dermis and a deeper muscle sheet, extending from the head to the thoracic inlet in mature pigeons. The slightly filled plexus is inconspicuous, resembling an ordinary venous bed, and consists of thick-walled veins having small lumina, similar to arteries. When moderately-filled, the veins of the plexus distend and abruptly transform into “beaded” veins with contorted, sacculated expansions separated by constricted segments. During heat stress, engorgement of the plexus occurs rapidly by continual flow over arteriovenous anastomoses that empty arterial blood directly into the beaded veins. Constriction of veins draining the plexus impedes venous return to the jugular veins, thereby maintaining tumescence of the plexus. Disgorgement of the plexus also occurs abruptly. Intimate contact between the deep aspect of the engorged plexus and the trachea and upper esophagus provides for heat transfer from the plexus to the mucosal surfaces of these structures where evaporative cooling takes place. During esophageal pulsation the esophageal surface extends and augments the respiratory dead-space area used for evaporative cooling. Thus a possible advantage of cooling by upper esophageal pulsation is that, like gular flutter of the oropharynx, it may minimize the amount of air that must pass over gas exchange surfaces, thereby limiting the washout of CO2 and consequent acid-base disturbances that occur during panting in extreme heat stress. Ability to inflate the esophagus is of general occurrence among the pigeons and doves (Family Columbidae). The collar plexus is also widespread, having been found in representatives of five of the examined six main subdivisions of the Columbidae.

Notizen: Summary 1. The development of taste hairs and tactile hairs of the fly Protophormia terraenovae is described using light microscope, scanning, and transmission electron microscope methods. 2. The development of taste hairs proceeds in the same way on tarsi, labella, and wings. First the dendritic outer segments of ciliary origin become visible above the hypodermal cell surface [2 days after pupariation (AP) at 19° C]; then the dendritic sheath starts growing out and finally the trichogen process follows. In a typical intermediate stage (‘stage C’) the distal sections of the dendrites float freely in the fluid surrounding the pharate adult. The more proximal sections are enclosed by the dendritic sheath around which the trichogen process is wrapped (4 days AP). The protruding dendrites disappear when the cuticle starts being deposited on the fully grown trichogen process, and the sheath vanishes later (9–10 days AP or 1 day before eclosion). The development is discussed with respect to the known structural organization of the adult hair. 3. In the tactile hairs the single dendrite which grows outwards is completely covered by the dendritic sheath and lies beside the trichogen process [stage C(m)]. 4. The taste and tactile hair development proceeds in the same way on legs isolated from the pupa after disc eversion in an artificial medium containing ecdysterone. 5. To check that both these patterns of development are widespread the development of taste and tactile hairs of the first instar cercus of the cricket Acheta domestica was studied with the light microscope: Both hair types pass through identical early stages.

Notizen: Summary The larval endostyle consists of two ridges of secretory cells, which correspond to the two paired muciparous bands in the endostyles of the adult Branchiostoma, most tunicates, and the lamprey ammocoete. The peculiar shape of the larval endostyle is an effective adaption for food-trapping in the asymmetrical body of the larva. Contrary to general belief, the internal opening of the club-shaped gland is the site of the secretory release, while the exernal opening is an inlet for sea water. The water is mixed with the mucous substance, probably containing neutral glycoproteins, which is produced in the gland tube. This material is released through the internal pore dorsally in the buccal cavity at a position where it is carried with the endostylar secretion towards the intestine. The club-shaped gland is not part of the food-trapping mechanism, but it is apparently an important larval gland which produces substances which may act in the processing of the food or in some other way may direct larval life.

Notizen: Summary Baker's yeast (Saccharomyces cerevisiae) suspended in the water that enters the incurrent canal system of the fresh-water sponge Ephydatia fluviatilis by way of the dermal pores is carried into the mesenchyme, where it is deposited against the surface of the flagellated chambers that generate the current. In the first phase of ingestion, as soon as the imported yeast cells have touched the choanocytes, the latter send extensive pseudopodia out into the mesenchymatic space to phagocytise the yeast cells there. Similar responses are elicited in the mesenchymatic cells during the second phase of ingestion and later in the pinacocytes of the excurrent canal system. All the cells of Ephydatia fluviatilis can phagocytise yeast cells. However, the yeast cells cannot be digested by the sponge cells and in the course of a few hours to 2 days they are expelled from the cells into the mesenchyme, whence they move transcytotically through the endopinacocyte lining into the excurrent canal system and eventually pass through the oscular tube to the exterior.

Notizen: Summary The tissues of a fully grown echinoid skeleton are described using the primary spines of E. tribuloides as an example. Cidaroid spines are covered with an external, polycrystalline cortex, but as long as they are still growing they are covered with an epithelium. The mineral skeleton is embedded in the mesodermal stroma tissue which largely consists of fluid. Different types of mesodermal cells float within this fluid, but the sole characteristic stroma cells are the sclerocytes which are anchored to the calcite trabeculae by means of a cytoplasmic stalk. The latter spreads over the surface of the young trabeculae as a thin, continuous sheath, but on fully grown trabeculae it ramifies into numerous filiform processes (dp). The sclerocyte cell body is surrounded by a boundary layer which, however, is absent in the distal sheaths or filiform processes. The cytoplasm of the sclerocytes is electron-translucent and contains numerous free ribosomes. Sclerocytes which lie below the epithelium produce the cortex layer, and in the end the extracortical stroma as well as the epithelium vanish, and the cortex becomes external. Phagocytes within the stroma are at least as numerous as sclerocytes. They have a dense cytoplasm with long, straight pseudopodia protruding from it and running through the midst of the pore space. In normal conditions the pseudopodia do not touch the trabeculae. In a single instance, however, a phagocyte was demonstrated to etch a trabecula. Its etching face was crowded with clear vesicles which are not found elsewhere.

Notizen: Summary Reabsorption of calcite is known to occur in echinoid endoskeletons. The structure of the operating cells is described using ‘Prouho's membrane’ as an example, which dissolves the skeleton of cidaroid spines within a thin section. After that the distal part of the spine is shed, and a new shaft grows out of the remaining stump. The calcoclast function is exercised by phagocytes which are also numerous in normal spine tissues. If the spine is highly damaged, however, the phagocytes assemble at a defined level and melt into a single syncytium, called Prouho's membrane. They fulfill three functions: (1) they show an extreme phagocytotic activity and ingest cells of the distal spine part, (2) they block off the surviving stump from the distal part shed later, (3) they etch through the calcite trabeculae in order to detach the distal spine part. The dissolution of the calcite starts with circular bulges, but in the end extremely thin etching lamellae run transversally through the trabeculae.

Notizen: Summary The ommatidia of the compund eye of the krill, Meganyctiphanes norvegica, are composed of the following cell types: corneagenous cells, main cone cells, accessory cone cells, distal pigment cells, and retinula cells. The corneagenous cells secrete the cuticular lenses, below which the crystalline cones are present. The bipartite crystalline cone is formed within the main cone cells, whereas the accessory cone cells invest the distal part of the cone and proceed proximally in the retina to the basement membrane. Six distal pigment cells are arranged around each ommatidium, though shared by adjacent ommatidia. The seven retinula cells form the rhabdom, and penetrate the basement membrane as axons. The basement membrane is formed by the conjoined extended prolongations from the accessory cone cells and sheets from the basal pigment cells.

Notizen: Summary Apodotrocha progenerans n.gen., n.sp. from tidal beaches or shallow waters on the east coast of the USA (Massachusetts) is a gonochoristic interstitial polychaete (length ca. 600 μm; six trunk segments), that lacks parapods, setae, and fleshy appendages, but has three characteristic caudal cirri. The habitus greatly resembles a larval stage of the Dorvilleidae, a family with which it also shares several anatomical features as revealed by ultrastructural investigations. Great similarities to the so-called archiannelids belonging to the Dinophilidae are also apparent, thus demonstrating the close phylogenetic relationship of the latter family to the Dorvilleidae.

Notizen: Summary The ovary of the red abalone consists of a series of trabeculae or polygonal chambers that extend from the ovarian wall toward the wall of the digestive gland. The ovarian wall consists of smooth muscle cells and bundles of collagen fibrils, that extend into the trabeculae. Presynthetic, synthetic and early postsynthetic oocytes are surrounded by a single layer of follicle cells which bind these oocytes to the trabeculae. The follicle cells contain bundles of microfilaments. Mature oocytes lack a follicle cell layer and are found free in the chambers formed by the trabeculae. Each oocyte is surrounded by a vitelline layer, a chorion, and a thick jelly coat. Stages in the formation of these layers are described. It is suggested that prior to spawning the trabeculae detach from the wall of the digestive gland and retract toward the ovarian wall. Contractions of the ovarian wall may force oocytes out of the ovary into the seawater where fertilization occurs.

Notizen: Summary The development of the aesthetascs of Neomysis integer (Malacostraca, Mysidacea) and Idotea baltica (Malacostraca, Isopoda) were investigated by electron microscope methods. Basically the aesthetascs of both species develop according to the same pattern. The newly formed sensillar shafts lie invaginated within the epidermal tissue. They are formed by numerous enveloping cells, which are arranged telescopically one by one. Each enveloping cell secretes a definite portion of the new shaft cuticle. The innermost enveloping cell extends furthest distally and deposits the cuticle of the future shaft tip. The outer enveloping cells produce the cuticle of the more proximal shaft portions. Whereas the morphogenesis of the aesthetascs of both species is uniform, the moulting processes are different. In the aesthetascs of Neomysis the morphological basis for a continuation of the sensitivity remains until ecdysis, as an intact dendritic connection between the sensory cells and the old shaft is maintained. In Idotea, the aesthetascs cease to function during the early moulting stages.

Notizen: Summary A structural and ultrastructural investigation of epidermis in the esophageal region of Carinoma tremaphoros is correlated with analysis of burrowing locomotion. The pseudostratified epidermis contains multiciliated epidermal cells, gland cells and granule-containing basal or interstitial cells resting on a well-developed basement membrane. Both circular and longitudinal muscles are present within the epidermis, woven between the cells of this layer. These muscles are well-developed along the anterior region of the worm and, like the subepidermal muscles, are a variation of obliquely striated muscle without continuous Z-rods. Epidermal muscles originate as branches from the underlying mesodermal musculature and cross the basement membrane into the epidermis, confirming earlier observations. These muscles are unrelated to myoepithelial epidermal cells described in other metazoans. This condition is considered a secondary derivation consistent with the Gastraea-Enterocoel theory of bilateral metazoan evolution. Carinoma is a peristaltic burrower. Peristaltic waves are limited to the anterior region of the worm where the diameter of the rhynchocoel is maximal and the bilayered epidermal musculature is strongly developed. Following a consideration of burrowing mechanics in annelids, supernumerary epidermal muscles in Carinoma are interpreted as prerequisites to peristaltic burrowing effectiveness in a non-segmented coelomate.

Notizen: Summary Light- and dark-adapted ocelli (LL and DD for 30 h) of seastars were studied by thin sectioning and freeze-fracture techniques for electron microscopy, and by histofluorescence. Lighting conditions affected the ultrastructure of the sensory microvilli, which became longer, more numerous, and more regularly arranged in darkness. A significant reduction in the density of intramembranous particles (IMPs) occurred in the sensory microvilli of LL specimens (6,600/µm2 in DD, 3,000/µm2 in LL) and, to a lesser extent, in the apical projections, but not in other membranous components including the cilia of the sensory cells. Additional observations on four other species revealed higher densities of IMPs in sensory microvilli than those in cilia. The fact that IMP densities of the LL sensory microvilli and the pinocytotic vesicles were nearly the same was considered to show the relationship of the two membranous structures. A specific fluorescence, indicative of the presence of retinal-based proteins, appeared only in the ocellar lumen of DD specimens, but practically none in LL ones. It was suggested that in the seastar ocelli the sensory microvilli are the primary photoreceptive sites and that they contain a rhodopsin-like substance. These conclusions support the view that asteroid photoreceptors are microvillar and not ciliary.

Notizen: Summary Rhabdom formation was examined at the EM level in two members of the Chrysomelidae with different patterns of open rhabdoms (Leptinotarsa decemlineata — ponticulus pattern; Crioceris asparagi — insula pattern). Rhabdom morphogenesis, especially that of the central rhabdomere system of R7 and R8 is slightly different in both species and does not reveal which of the two patterns is primitive and which is derived. A close spatio-temporal correlation was found in L. decemlineata between the occurrence of a transitory modified cilium and the beginning of rhabdomere formation. The significance of this finding and its possible functional implications for the development of insect photoreceptor cells are discussed.

Notizen: Summary The morphology of sternal glands and associated cuticular specializations are described for female polistine social wasps. Their distribution among 25 of the 28 genera of the subfamily is examined in light of what is known of the functions of these glands. Species in which queens found colonies independently of workers (four genera plus part of Ropalidia) have clusters of ducted gland cells on the sixth (terminal) gastral sternite. In all species examined the gland cells open into a tuft of long setae which probably functions as a reservoir/applicator brush. There is at least circumstantial evidence for all five genera that this gland produces an ant repellent substance that is smeared onto the nest petiole, where it serves as a defensive barrier against ants. The remaining genera (20 plus part of Ropalidia) consist of species in which queens are accompanied by a swarm of workers in the initiation of a new colony. In 12 of these genera females have a gland of ducted cells on sternite 5 (penultimate), associated with cuticular sculpturing of various types. Experimental or circumstantial evidence for several of these genera indicates that the product of this gland is used to lay an odor trail that guides the swarm from the parent nest to a new nest site. One genus has a similar gland on the sixth sternite, another has glands on both the fifth and the sixth, and the remaining six genera lack any evidence of sternal glands. The independent-founding species of Ropalidia have a sixth sternal gland associated with a tuft of setae, while the swarm-founding species have the tuft but lack the gland. Our interpretation of this is that the gland produces an ant repellent substance in the independent-founding species, but in the swarm-founding Ropalidia such a substance is of little value and so the gland has been lost.

Notizen: Summary The flow of stained haemolymph was photographed in the wings of resting Pieris rapae, Pieris brassicae, and Gonepteryx rhamni under UV-radiation at definite intervals after abdominal application of fluorescent tetracycline. There is no circular route in the wing. All wing veins are supplied with stained haemolymph from their own bases without preference to single veins. In freely resting Pieris with intact wings, most veins are completely stained after 20 min. The staining pattern supports the existence of an oscillating haemolymph supply mechanism in the wing veins and shows that the cross vein and encircling sinus are not essential in the supply of the longitudinal veins. Inflow of stained haemolymph into the wing membrane begins about 1 h after application and is generally completed within 12 h in Pieris. The wing membrane is supplied with fluid by diffusion and — especially under low relative humidity — additionally by haemolymph substitution of evaporated water. This mechanism is associated with the disadvantages of water loss and probably salt withdrawal from the body. The puddling behaviour of butterflies might help in restoring these postulated deficits. It is hypothesized that haemolymph substitution of water evaporated from the wing membrane is a preadaptation for accumulation of defensive toxins and pheromones in the wing membranes, especially in diurnal and basking Lepidoptera. The veinal system of 5-day-old young summer specimens of Gonepteryx stains more intensely than that of 4–5-month-old specimens just before entering hibernation. The transition of stained haemolymph from vein to membrane is reduced in this species, probably as an adaptation for water retention during diapauses.

Notizen: Summary The majority of large, bilaterally-symmetric animals possess two structurally distinct systems of internal fluid transport, the coelomic circulatory system and the blood vascular system (BVS). The coelomic circulatory system is generally situated laterally, lined by a continuous layer of mesodermally-derived cells and moves fluid with cilia or body wall muscles. The BVS occurs in extracellular matrix with the principal vessels situated dorsally and ventrally. The vessels are typically unlined by cells. Fluid is propelled by contraction of overlying muscle cells. Co-occurrence of two systems of internal fluid transport is explained by a segmentation hypothesis: Most large, triploblastic animals are segmented with at least two or three fluid-filled compartments separated by septal bulkheads. Because exchange surfaces (gas, nutrient) are regionally restricted, selective pressure favors a fluid transport system that bridges septal bulkheads. The BVS fulfills this requirement because it is situated in extracellular matrix that is non-cellular and continuous throughout organisms. A survey of animals indicates that all segmented taxa possess a BVS, except Sipuncula, where compensation sacs function as BVS analogues. Loss of the BVS in Hirudinea and other annelids is correlated with the disappearance of septa. Funicular vessels in Bryozoa are compared with BVS in other lophophorates. The fluid transport system of Nemertini and some platyhelminths is shown to conform to the definition of a coelomic circulatory system. This investigation supports Liwanow's proposition that the BVS evolved as the progressive modification of extracellular matrix in triploblastic animals. Evolution of coelomic circulatory systems is unresolved.

Notizen: Summary Spermiogenesis and sperm cells of the meiobenthic priapulid Tubiluchus were described by means of the transmission electron microscope. The sperm cells are completely different from the male gametes of Priapulus, being elongated and thus indicating a different mode of sperm transfer. The anterior portion of the sperm head is characterised by a corkscrew configuration of nucleus and acrosome, both components being wrapped around each other. This kind of sperm cell has never been reported in other animal phyla.

Notizen: Summary Freeze fracture preparations of the Branchiostoma epidermis revealed a number of specialisations of the plasma membrane. The highest number of intramembrane particles were found in the membrane of the microvilli, where they are predominantly localised in the P-face. In connection with the apical membrane an extracellular coat of complex branched filamentous structures (about 1.5 μm thick) can be demonstrated which was seen in carefully prepared transmission electron micrographs. In the area of the septate junction, the lateral plasma membranes are endowed with large numbers of variously sized membrane particles in the P-face which may form indistinct, short particle rows. The E-face is poor in particles. The freeze fracture image of this junction differs markedly from that of the mollusc-arthropod septate junction and bears similarities with the hemichordate and echinoderm septate junctions. Patches of particle aggregations suggest the presence of desmosomal contacts in the lateral membrane. No occluding or communicating junctions were found.

Notizen: Summary The early development of taste sensilla has been studied with special emphasis on cilia, dendrite, and pore formation. In the 39-h stage (the first stage investigated) differentiation of sensilla is already under way. The mechanisms of differentiation of dendrites (39–48 h) deviate from the mechanisms described for differentiation of “true” cilia. In taste hairs the centrioles meet in the tip of the narrowed apical region of the sensory neuron. Together they sink deeper into this region and line up coaxially, thus forming the basal body complex. Thereafter, lateral contacts between this complex and the plasma membrane of the neuron are established. Formation of open connections between the trichogen lumen of the hair and the environment, or the dendrite lumen, was not observed. Electrophysiological data indicate that the sensilla become functional from 3 days before emergence onwards.

Notizen: Summary The fine structure of a paired lamellate body in the anterior region of the lycophora larva of Gyrocotyle urna is described. Each structure is built up by one specialized cell. Lamellae derive from membranes of about 15 cilia that protrude into an intracellular cavity. The lamellae divide into several flattened branches and are rolled up forming a whorl. The lamellate body is presumed to have photoreceptory function. Comparative deliberations are made for similar structures within several platyhelminths.

Notizen: Summary The specialized adhesive exumbrellar tentacles of the limnomedusa Vallentinia gabriella were examined by light microscopy and scanning and transmission electron microscopy. The adhesive region first differentiates some distance from the tentacle tip. As differentiation proceeds the distal part is reduced and the adhesive region comes to lie at the tentacle tip. The adhesive epithelium consists of flagellated and non-flagellated glandular cells, a few nematocytes, and a nerve plexus. The glandular cells are characterized by electron-dense granules and bundles of microtubules. The microtubules, being anchored to the mesoglea, are oriented parallel to the longitudinal axis of the cell and extend up to the cell apex. It can be assumed that the microtubules are involved in the transport of secretory granules to the cell apex. Bundles of neurites run adjacent to the mesoglea between the basal processes of the glandular cells. The neurites form interneural synapses and synapses with glandular cells. It is suggested that detachment of the specialized adhesive tentacles is under nervous control.

Notizen: Summary The topography of the funnel-canal organs of Carcinus maenas (Decapoda, Crustacea) and their stimulus-receiving cuticular and sensory apparatus were studied in the light and electron microscopes. About 4000 funnel-canal organs are situated within the exoskeleton of Carcinus. Almost all of them are on the distal segments of the walking legs, in particular on the epicuticular cap at the tip of the dactyl. They were not found to be arranged in groups or sensilla fields, and no sex-specific differences were observed. Characteristic features of the funnel-canal organs are as follows: (a) There is a terminal pore (0.5×0.8 μm diameter) in the cuticle, at the tip of a small projection. It is closed by a plug of electron-dense material. (b) The terminal sections of the dendrites are enclosed in a dendritic sheath up to ca. 10 μm below the pore. (c) The dendrites, 3–24 in number, end below the plug; none of the dendrites exhibits a tubular body; two of the dendrites are distinguished from the others by the greater number of microtubules in their outer segments. The structural characteristics, in particular the “gustatory pore” and the number of dendrites, are typical of bimodal receptors in arthropods. In such receptors, as in the contact chemoreceptors of insects and arachnids, mechano-and chemosensitive sensory cells are combined. This interpretation of the function of the funnel-canal organs is supported by electrophysiological data of other authors. The morphological parameters we find for the funnelcanal organs, in comparison with those of insect campaniform sensilla, provide clear evidence against the reclassification of the funnel-canal organs as “crustacean campaniform organs” proposed by Shelton and Laverack (1968).

Notizen: Summary Post-embryonic development of parthenogenic eggs of Lepidodermella squammata was studied by light and electron microscopy in animals of known age and reproductive history. Each bilateral gonad initially contains eight cells. No mitotic proliferation occurs during parthenogenic egg development. Germ cells are tightly clustered, have smooth plasma membranes with no interconnections, and are uninucleate. There is no surrounding ovary or oviduct. At hatching, two cells in each gonad are identifiable as parthenogenic eggs. The enlarged nucleolus of the most mature egg has already attained the morphology that persists throughout vitellogenesis, with intertwined granular and fibrillar threads. Less mature eggs have earlier stages of nucleolar development, and lack indications of meiotic events. Parthenogenic eggs enter vitellogenesis singly, with formation of RER and active Golgi complexes, and the accumulation of lipid, yolk, and various granules. The shell is formed in situ, whereas the spines elongate after egg deposition. Most animals produce four parthenogenic eggs, which undergo immediate development (tachyblastic eggs). Resting (opsiblastic) eggs are rare in isolation culture. Both types of eggs are produced only prior to the formation of sperm and primary oocytes. The absence of synaptonemal complexes, which would indicate synapsis of homologous chromosomes in prophase of meiosis I, implies that parthenogenesis is by apomixis in L. squammata.

Notizen: Summary The anatomy of the cecum of the West Indian manatee (Trichechus manatus) is described at the macroscopic and microscopic levels. The cecum possesses a voluminous corpus ceci with two lateral outpocketings; two diverticulae (cecal horns) extend from the corpus at the vicinity of the ileocecal junction. An ampulla ceci is found distal to the corpus ceci, the two compartments communicating via a wide-opened orifice. The most striking microscopic finding is the mucosal covering of a keratinized stratified squamous epithelium overlying the crypts of Lieberkühn. An attempt is made to interpret the morphological observations in terms of the functional digestive process in the manatee, giving alternative suggestions concerning the significance of the cecum and colon in the nutritional status of the manatee.

Notizen: Summary The gemmule shells of fresh-water sponges have a species-specific surface structure, described here for three spongillid species by reference to scanning electron micrographs. The internal structure of the shell is revealed in scanning electron micrographs of sectioned shells released from the embedding medium. Pictures obtained by this method (Weissenfels 1982a) provide information about the architecture of the gemmule shells and the development of the so-called compartmented layer in the gemmule shells of Spongilla fragilis.

Notizen: Summary Histology, physiological regeneration, and degradation of the taenioglossan prosobranch radula and its concomitant epithelia were studied by light and electron microscopy (TEM, SEM), electron microprobe analysis, and autoradiography. Taenioglossa have seven multicellular odontoblastic cushions which produce the tooth matrix by apocrine secretion; many long microvilli are also incorporated. In contrast to pulmonates, the odontoblasts of prosobranchs are capable of division, and their mitoses contribute to the expansion of the cushions, but presumably also to the displacement of degenerating odontoblasts. The seven cushions are isolated from each other by separation cells. The radular membrane is produced from microvilli of membranoblasts and a substance secreted at the base of microvilli. Strands of the supraradular epithelium subsequently move in between the teeth and finally enclose them completely. They effect the hardening and mineralization of the teeth. The strands move together with the radula towards the anterior and are extruded at the opening of the radular sheath; their degeneration, however, has already started in the middle section of the sheath. Epithelial cells are produced by two completely separated mitotic centres which lie dorsolaterally at the end of the sheath. In the subradular epithelium, mitotic activity is scattered over the posterior half of the sheath but is not found in the region where the supramedian radula tensor muscle is inserted. The epithelial cells move forward, but at a much lower rate than the radula. At the opening of the sheath the subradular membrane is generated, while cells of the subradular epithelium lying between the lamellae of the subradular membrane are extruded. The subradular membrane is limited to the functional part of the radula. It is situated on the distal radular epithelium, which is obviously not a continuation of the subradular epithelium. In test animals treated with tritiated thymidine, there is a very strong stationary centre of labeled cells at the beginning of the epithelium, but so far no mitoses have been found in this centre and the labeled cells do not move on continually. In the middle of the distal epithelium mitoses do occur, and the labeled cells permit the assumption that these cells do not migrate at all to the anterior end. At least in Prosobranchia, the distal radular epithelium does not transport the radula to its degradation zone. The transport mechanism for the radula is still unknown.

Notizen: Summary Besides the two axial fibers and the mass of cribellum fibrils, a third component is present in the capture threads of uloborids. This is a substructure originating from the paracribellum. It probably helps to fasten the axial fibers in their position. The axial fibers are secreted from the two glandulae pseudoflagelliformes whose spigots are situated on the posterior spinnerets. It is hypothesized that the cribellum fibrils become jammed and thus fixed between the axial fibers by periodical abduction and adduction of these spinnerets.

Notizen: Summary Processes occurring during moulting in Tetranychus urticae (Acari, Tetranychidae) are described by means of electron microscopy. Moulting is characterized by a pre-ecdysial phase which is initiated by the detachment of cuticle and epidermis. Epicuticular material is deposited as plaques but fuses to form a continuous layer. The epidermis folds up and ridges become determined. Procuticular material is synthesized inside the epidermis and packed into granules which accumulate below the epicuticular portions already deposited. Prior to ecdysis, portions of the old cuticle are dissolved. Ecdysis is achieved by moulting glands which effect bursting of the old cuticle. During the post-ecdysial phase, the endocuticle is synthesized during which a lamellation becomes obvious. Processes occuring during moulting are compared to published information on the tick cuticle.

Notizen: Summary In addition to a male copulatory organ containing a stylet, Polystyliphora filum has numerous uniform prostatoid organs which are arranged in series caudally to the copulatory organ. Each of these prostatoid organs consists of a stylet, extending into an atrium, and caudal to this a bulb. The stylet is funnel-shaped with a curved distal part and a flattened projection in the middle; funnel and projection are differentiated together in a single cell. In an early phase of differentiation, a framework of microtubules is built in the basal part, and this becomes enveloped by electron-dense material. In a later phase, the space between the formed hard structure and the outer membrane of the style building cell is partially filled up with electrondense material. The distal part of the stylet if formed by electron-dense material taken up to the outer membrane. The whole hard structure is differentiated simultaneously and intracellularly. At the same time the whole muscular system of the prostatoid organ is formed. The completed prostatoid organs do not contain sperm, but much coarsegrained medium electron-dense secretion.

Notizen: Summary Mature sperm of the three species, Onithochiton quercinus, Chiton pelliserpentis and Plaxiphora paeteliana are eupyrene and basically of the “primitive” type. The sperm are small, with a distinct head, midpiece with a few spherical to oval mitochondria and a long tail with a (2×9)+2 axoneme. They are unusual among primitive sperm in being bilaterally symmetrical, with a long anterior filament containing an extension of the nucleus and lacking an acrosome. Spermatogenesis occurs synchronously throughout the testis in inwardly folded tissue plates. Spermatogonia arise adjacent to the central blood sinus in each tissue plate. Cells in successive stages of spermatogenesis are displaced towards the luminal surface. The cytoplasm of all stages contains ribosomes, rough endoplasmic reticulum, lysosomes and mitochondria. A Golgi complex is present in secondary spermatocytes and spermatids but does not form an acrosome. During spermiogenesis Golgi complexes are confined to the posterior region of developing sperm and are eventually shed in the residual cytoplasm behind the midpiece. Preacrosomal vesicles are not formed. The long anterior filament of the sperm and lack of an acrosome are features associated with the fertilization of eggs surrounded by a chorion which may have pores or a micropyle. The exact method of fertilization in chitons remains to be elucidated.

Notizen: Summary Marthasterias glacialis bears two kinds of pedicellariae. The straight pedicellariae are single and occur everywhere on the asteroid body surface except in the ambulacral groove. The crossed pedicellariae are clustered on mobile structures (the rosettes) build around marginal and abactinal spines. Basically, each pedicellaria has a head and a stalk. A skeleton occurs only in the pedicellarial head. It consists of two valves and a basal piece. Muscular bundles are anchored on these skeletal ossicles. The straight pedicellariae have two pairs of adductor muscles (the inner and the outer adductors) and one pair of abductor muscles, these latter being weakly developed. Longitudinal muscle fibers occur all along the stalk of straight pedicellariae. The crossed pedicellariae have two pairs of adductor muscles (the distal and the proximal adductors) and two pairs of abductor muscles (the distal and the proximal abductors). The proximal adductors of crossed pedicellariae are homologous to the stalk muscles of straight pedicellariae. The pedicellariae are able to react to direct and indirect tactile stimuli. There is a great deal of individual variation among pedicellarial responses. Moreover, the reactions occur at random and lack coordination. The seemingly aberrant behavior of the pedicellariae is interpreted as a preventive activity that protects the asteroid body surface against unwanted materials and organisms.

Notizen: Summary The cephalic sensory organ in the veliger larva of Rostanga pulchra is situated dorsally between the rhinophores, emerging as a tuft of cilia. This organ is made up of three types of sensory cells, and based on their morphology have been termed ampullary, parampullary and ciliary tuft cells. The cell bodies of the organ originate in the cerebral commissure, and their dendrites pass to the epidermis as three tracts. Dendrites terminate in the epidermis to form a sectorial field. Axons of these cells run into the mass of neurites in the cerebral commissure but no synapses were observed in this area. Morphological evidence suggests that the cephalic sensory organ may function in chemoreception and mechanoreception related to substrate selection at settlement, feeding, or other behaviors.

Notizen: Summary Olfactory trichoid hairs on the antennae of male Antheraea silkmoths were reconstructed with respect to the following parameters: number, shape, course, and dimensions of outer dendritic segments as well as the numbers of their microtubules; inner and outer dimensions of the cuticular hair shafts; and number and distribution of pores and pore tubules in the hair walls. The smallest distances between dendritic membranes and inner hair surfaces were determined with respect to the possibility of pore tubule contacts. It was shown that most hairs contain one thick and one, or frequently two, thin dendrites. The number of microtubules in the dendrites is correlated with dendrite diameter, which decreases towards the hair tip. The dendrites form numerous swellings and constrictions: this “beading” occurs especially along the thin dendrites. The dendrites do not run straight, but rather follow a sinuous course in the hairs. The density of wall pores is lowest in the basal region of the hairs. Only in relatively few places do the dendritic membranes get near enough the hair walls to come into the probable range of the pore tubules. In the sensilla trichodea of A. polyphemus, the hairs as well as the dendrites have markedly smaller diameters than in A. pernyi.

Notizen: Summary Differentiation of spermatids to mature spermatozoa in the bryozoan Tubulipora liliacea was studied by transmission electron microscopy. The spermatozoon of Tubulipora is of a filiform, modified type, and has evolved from the primitive type as an adaptation to a specialized biology of fertilization. The head of the spermatozoon consists of a small, conical acrosome capping an elongated, cylindrical, anteriorly tapering nucleus. A basal invagination in the nucleus contains the proximal portion of the axoneme and a dense attachment matrix. The flagellar axoneme has the typical 9+2 structure. Four elongated rodshaped mitochondria with typical cristae surround the axoneme in the cylindrical middle piece. Granular electron-dense material is accumulated in the form of four columns alternating with four long cylindrical mitochondria. The mitochondrial middle piece is separated externally from the tail region by an involution of the plasma membrane. The tail region contains a cytoplasmic sheath with accessory fibers surrounding the axoneme. Nine outer, coarse fibers extend posteriorly paralleling the nine doublets of the axoneme. The coarse fibers develop from electron-dense plate-like structures associated with the doublets of the axoneme. A characteristic feature in spermiogenesis is that spermatozoa develop in tetrads. There seem to be significant differences in spermatozoan ultrastructure between the three bryozoan classes Stenolaemata, Gymnolaemata, and Phylactolaemata. The differences indicate different lines of evolution of fertilization biology in these groups.

Notizen: Summary The morphology of the retinal pigment epithelium (RPE) and adjacent choroid has been investigated by electron microscopy in the domestic pig. The RPE consists of a single layer of cells which are columnar posteriorly but become cuboidal and even squamous moving peripherally in the fundus. The cells of the RPE layer regardless of location display basal (scleral) infoldings and apical (vitreal) processes and are joined laterally by junctional complexes. Throughout the retina the epithelial cells are rich in smooth endoplasmic reticulum and mitochondria but less so in rough endoplasmic reticulum and polysomes. The epithelial nucleus is vesicular and basally located. In the superior fundus an area of the RPE is very lightly pigmented and richer in lysosomes than is this layer in the inferior and peripheral fundus. The choroid overlying this area is also lightly pigmented and contains much collagen in a lamellar arrangement. This region may represent a vestigial tapetum fibrosum. Bruch's membrane is slightly thicker posteriorly but is everywhere seen to have a pentalaminate substructure. The choriocapillaris is a single layer of large capillaries which show numerous fenestrations facing the RPE. In the superior fundus the choriocapillaris is also highly fenestrated facing the choroid.

Notizen: Summary The pacemakers responsible for initiation of swimming contractions in cubomedusae are located in the four rhopalia. Interneuronal synapses occur between the rhopalial ganglia and the retina cells of lens and cup eyes on one side and the cells of the marginal nerve ring on the other side. Neurites pass from the nerve ring to the neurons of the subumbrellar nerve net synapsing onto muscle cells. The pacemaker system (rhopalial ganglion) is composed of neurons (ganglion cells) containing Nissl's granules. Numerous neurons (interneurons and motoneurons) and nerve fibers make up the nerve ring, most of them oriented parallel to its circular path. While all interneural synaptic contacts are symmetrical, the neuromuscular synapses and contacts between retina cells are asymmetrical (=polarized).

Notizen: Summary A conus-like structure, the hyaloid conus, located on the optic nerve head of the mesopelagic deep-sea teleost Radiicephalus elongatus is described. The hyaloid conus consists of a tapering sheath of unpigmented, vascularized connective tissue enveloping the proximal part of the hyaloid artery which proceeds from the optic nerve head through the vitreous body to the ventrally located falciform process and lens muscles. The hyaloid artery passes through the hyaloid conus without giving off any branches. The conus vessels encircling the hyaloid artery receive arterial blood from the choroid via small arteries and are drained to the choroid by a single vein. The hyaloid conus is compared with the lacertilian conus papillaris. The function of the hyaloid conus is unknown. Because of its small dimensions relative to those of the eyeball and its few capillaries, it is unlikely that the hyaloid conus is a supplemental nutritive device for the retina.

Notizen: Summary The structure of the setae on the proximal antennal segments of the beetle Loricera pilicornis is described using electron microscopical methods. These setae are part of a prey-capturing apparatus and are inserted within flexible sockets. They have no central lumen. Four or five sensory cells are connected to each seta. One cell is characterized as a mechanoreceptor due to the presence of a tubular body and the location of its dendritic outer segment. The other sensory cells are of two types. One type shows the usual features of sensillar receptors except that the dendritic outer segments end beneath the seta within the cuticular sheath. In the other type all parts of the cell, including the perikaryon, appear undersized, and no axon was found. In a single case a sixth cell was found which lacks any process, although, due to its location, it belongs to the sensory cell group. The enveloping cells also deviate from the usual pattern. Trichogen and tormogen cells have no membrane folds nor microvilli. From the membrane of the thecogen cell, where it borders on the inner receptor lymph cavity, invaginations have developed which form voluminous membrane whorls. Portasomes are found on these membranes. On the basis of the structural features we hypothesize that the setae represent sensilla undergoing stepwise reduction, losing primordial gustatory units whilst the prey-capturing mechanism is optimized.

Notizen: Summary The morphology of the rete ophthalmicum, which functions as a brain cooling system, was studied in the desert-origin Bedouin fowl in comparison with two commercial breeds: the White Leghorn and the White Plymouth Rock. Cross-sections of the rete ophthalmicum revealed a significantly higher degree of arteriovenous contact in the Bedouin fowl than in the commercial breeds (P〈0.01). Based on the allometric relationship between the heat exchange area in the rete and body weight, the Bedouin fowl has a significantly higher heat exchange area than non-Bedouin fowls of similar body weights (P〈0.02). These findings suggest that the higher heat exchange area and the high degree of arteriovenous contact in the rete ophthalmicum of the Bedouin fowl is an adaptation to desert conditions, and contributes functionally to the apparently superior heat resistance in this desert breed.

Notizen: Summary In flies, for example the blowfly Calliphora erythrocephala, the thorax has fused to form a chitinous capsule. In it we find three functional types of flight muscles, the indirect flight muscles, the direct, and the tension muscles. The indirect or wing beat muscles transfer their power to the capsule which is capable of oscillating. They are suspended nearly “horizontally” and “vertically”. The direct muscles used for steering insert laterally on the capsule and go to the wing joint. The third functional type of flight muscle serves to put the lateral walls of the thorax under tension. The site and morphology of the flight muscles are described in detail, making use of 3-dimensional drawings. The flight muscles of Calliphora erythrocephala (Heide 1968) and their functions are compared with those of other dipterans described by different authors.

Notizen: Summary The structure of the ocelli of the interstitial gastropod Fartulum orcutti was studied using light and electron microscopy. Each eye is composed of pigmented, rhabdomeric, and ciliated cells. The pigmented cells contain many electron-dense granules and form a cup that shades the sensory cells from all light except that entering from a dorsal-anterior direction. The rhabdomeric cells are similar to the photosensory cells described for other gastropods. They contain photic vesicles and are characterized by an array of microvilli that project into the interior of the eyecup. In the ciliated cells, the ciliary membranes are greatly expanded and form whorls that lie at the front of the eye, opposite the pigment cup. Axons from the bases of rhabdomeric cells have been traced into the optic ganglion, whereas nerve connections from the ciliated cells have not been observed. We suggest that both the rhabdomeric and ciliated cells are photosensory based on their morphological similarities to eyes in other invertebrates. The significance of ocelli with two types of sensory cells is discussed with regard to 1) phylogenetic schemes based on photoreceptor morphology, and 2) the function of such eyes in the interstitial habitat. In addition, the structure of the eye in Fartulum is compared with the description at the light microscopical level of the eye of a related interstitial gastropod.

Notizen: Summary The filtering surface of the branchial basket of Ascidia paratropa (Huntsman, 1912) consists of two adjacent and connected sheets. The stigmatal surface is loosely folded. The secondary gill screen, composed of ciliated longitudinal vessels with primary and secondary papillae, is connected to the stigmatal surface on the inside of the branchial basket. Continuous mucus secretion results in a net with elastic and adhesive properties, and a pore size of less than 0.5 μm in its longest dimension. Net production cannot be interrupted by external mechanical stimuli. The net is usually supported by and transported across the secondary screen, forming a filtering surface that parallels the undulations of the stigmatal surface; however, localized muscular activity of the dorsal laminar fold and longitudinal vessels are also involved in mucous net transport. Squirts occur more frequently than in many species. At these times the net is transported as a flat sheet, independent of the secondary screen. Squiring does not interrupt continuous feeding activity.

Notizen: Summary Retinae of the secondary eyes of a primitive salticid spider, Yaginumanis sexdentatus (Yaginuma 1967) are described at the ultrastructural level. The structures of the anterior lateral, posterior lateral and posterior median eyes are identical. Receptor somata lie in the retinal cups. Each receptor bearing twin rhabdomeres is ensheated by (i) much-divided processes of non-pigmented glial cells whose somata lie distally in the retinal cups; and (ii) four processes of pigmented glial cells whose somata lie basally, below the receptive segments. Pigment granules in the latter are concentrated in the basal retina, and are not present at the level of the rhabdoms. The present findings support the placement of Yaginumanis in a newly erected Subfamily Spartaeinae by Wanless (1984), because of the likelihood of homology in the fine structural organisation of the secondary retinae of this genus and of the genus Portia.

Notizen: Summary The mechanical implications of various types of slit arrangements found among the strain-sensitive slit sensilla in the arachnid exoskeleton (Fig. 3) were studied by measuring the deformation of model slits, cut into plastic discs, under static load applied in the plane of the disc and from varying directions (Figs. 1, 2). 1. Close parallel, lyriform arrangements. Compression of slits (adequate stimulus) reaches much higher values than dilatation. It is highest with the load direction at right angle to the slit axes. Also, in the majority of slits the range of load angles resulting in compression is considerably larger than that leading to dilatation. Length distribution and lateral shift of slits in the models have a pronounced effect on slit deformability (Figs. 4-5): (a) In the “oblique bar” arrangement with slits of equal length and regular lateral shift (Fig. 4A) deformation of all slits is very similar at all load directions. In all slits compression results from a range of load angles larger than 120°. (b) In arrangements with a regular increase in slit length and a triangular outline shape deformability differs greatly among the slits at all load angles (Fig. 4B). (c) The slit configuration with a heartshaped outline (Fig. 4C) is peculiar for the large spread of load angles at which the compression of the different slits is highest. — These properties recommend different arrangements for the solution of different strain measuring problems, with for instance, the particular need of a wide angular working range (arrangement a), of a large spectrum of absolute sensitivities (b), or of the analysis of load direction (c). 2. Angle and distance between slits. Due to the mechanical directionality inherent in an elongated slit the divergence of slit axes within a group of slits is likely to indicate the importance of the analysis of strain direction (Fig. 6). The mechanical interaction between closely neighbouring slits decreases with their distance from each other. In a parallel arrangement of equally long slits it disappears if the distance is about 1.5 times the slit length (Fig. 7). 3. Aiming towards a mechanical model which would explain the complex deformation found in a lyriform organ, we consider the outline of the organ as a hole traversed by beams of material. Slit deformation can be calculated from the elastic lines of the beams which separate the slits and information drawn from photoelastic experiments (Figs. 8-11).

Notizen: Summary Scanning EM investigation of posterio-lateral parts of teleostean fish scales showed that the membranes of their surface epithelium are covered by a complicated system of tuberculi and ridges, forming a maze-system over their cells. These ridges, which are 0.4–0.7 μm high and 0.2–0.6 μm wide, constitute swellings of the cell membrane and form a pattern comparative to the ridge-system found on the skin of higher vertebrates. Epithelial prints of this type were investigated in 43 species of fresh water fish (Cichlidae, Characidae) and marine fish (Serranidae, Apogonidae, Sparidae, Scorpaenidae, Pomacentridae, Girellidae, Gobiidae) of America, Africa, and Asia. The ridge-prints were found to be species-specific, if observed over scales of the same body-site for all individuals. Our investigation, especially on species of the California rockfish (Sebastes), showed that within a given taxonomic group the structure of the ridges is in accordance with the taxonomic as well as ecological relationships of the species involved, usually being more developed in active swimmers and reduced or absent in sessile forms. This research demonstrated that the skin surface microstructures can be used for evolutionary-ecological studies.

Notizen: Summary In the Nematoplanidae and the Polystyliphoridae (Proseriata) a special collar receptor type is found, which differs in two points from the basic pattern of these receptors in the other Proseriata and in the Rhabdocoela: (1) The receptors run between epidermal cells to the surface. (2) In the distal region of the receptor cells an electron-dense cuff is developed. The cuff of these receptors, together with some other features of organisation, is considered to be a synapomorphy of the Nematoplanidae and the Polystyliphoridae, which together form the monophyletic taxon Unguiphora Sopott-Ehlers, 1984.

Notizen: Summary The muscle receptor organs of the mandible of Leuctra extend between the anterior tentorial arm and the mandible base. The ventral receptor is composed of two thin muscle fibres (6–7 μm in diameter) and at least ten multiterminal sensory cells, the dendrites of which branch in the interior of the fibres and end near the z-bands. The dorsal receptor organ consists of three muscle fibres of similar diameter and only one multiterminal sensory cell. The dendritic ends lie at the distal end of the muscle, where muscle fibres and epidermal cells make contact. Both receptor organs essentially show the same ultrastructural characteristics as in Coleoptera. However, the dorsal receptor organ in particular possesses organelles in its dendritic ends, which look like the tubular bodies in ciliary mechanoreceptors.

Notizen: Summary A comparative ultrastructural study of the copulatory organ was carried out in four genera of Turbellaria-Monocelididae. In all four genera the male copulatory organ is of the conjuncta-duplex type and has a cirrus armed with spines. Fine-structural analysis of the cirrus spines reveals that these structures are specializations within the basement lamina of the cirrus. In this part of the male canal the basement lamina has a trilamellar structure. The spines are formed by a local thickening of the middle electron-dense layer and show a structural similarity in all the Monocelididae investigated. The systematic value of this character within the family Monocelididae is discussed.

Notizen: Summary The anatomical and histological details of the respiratory organs and the vascular system of Phyllidia pulitzeri Pruvot-Fol, 1962, are described. The vascular system, especially of the ventral “gill” leaflets, is reconstructed and compared with that of typical Doridacea (Archidoris and Corambe). Within the Phyllidiidae the sinus lateralis maintains its function of returning the blood from the notum to the atrium. This blood is oxygenated by cutaneous respiration. The sinus lateralis also returns the blood from the ventral leaflets. The caudo-medial entrances of the afferent and efferent branchial vessels into the atrium, so typical of all gill-bearing Doridacea, are missing in the Phyllidiidae. The position of the respiratory organs, the mode of multiplication of the “gill” leaflets, the lack of the raphe and of an independent branchial vascular system, and the enlargement of the peripheral vascular system into ventral leaflets show that the “gills” of Phyllidia pulitzeri are secondary specializations of the epithelium of the ventral notum. The heart and the sinus laterales lying bilaterally symmetrical on the viscera, the vascular system, and the respiratory organs seem to be apomorphic features that evolved only once within the Doridacea.

Notizen: Summary The gut of a crinoid echinoderm is described for the first time by transmission electron microscopy. The gut comprises a short esophagus, a relatively long intestine and a short rectum. From the luminal side to the coelomic side, the layers of the gut wall are an inner epithelium, an epineural plexus (much reduced or absent in the intestine and rectum), haemal fluid, smooth muscles mixed with a hyponeural plexus, and a visceral peritoneum. The inner epithelium of the esophagus consists of numerous flagellated enterocytes and some mucous cells containing abundant mucous granules. The luminal surface of the esophagus, but not that of the other gut regions, is covered by a conspicuous cuticle. The inner epithelium of the intestine consists of some exocrine cells, presumably exporting digestive enzymes to the gut lumen, and numerous vesicular enterocytes that are flagellated and contain a few apical mucous granules. The inner epithelium of the rectum is made up entirely of vesicular enterocytes most of which lack a flagellum. The uptake of macromolecules from the gut lumen was demonstrated by feeding the feather stars food mixed with ferritin. By 4 h after feeding, ferritin was identified in presumed secondary lysosomes within the enterocytes of the esophagus and within the vesicular enterocytes of the intestine and rectum. The functional implications of the new fine structural results are discussed.

Notizen: Summary (1) Scanning electron microscopy and vascular casting were used to study the morphology and vascular anatomy of the fully developed internal gills of Litoria ewingii tadpoles. — (2) The four pairs of gills were located in two branchial baskets on either side of the heart. Each gill consisted of a branchial arch with gill tufts projecting ventrally and gill filters running dorsally. The gills bore a variable number of gill tufts in which a complex three-dimensional array of capillary loops, of varying lengths and diameters, was trailed in the path of the ventilatory current. — (3) The evidence presented in this paper suggests that the gill tufts have greater potential as gas exchangers than either the gill filters or skin. — (4) The study revealed structural and functional evidence for the existence of branchial shunts between afferent and efferent branchial arteries.

Notizen: Summary The fresh water sponge Ephydatia fluviatilis contracts rhythmically. At 15° or 16° C the frequency of contraction varies between 4–6 h; the contraction itself takes about 1 or 2 h. Increasing water temperature from 15° to 19° C causes irregular additional contractions, which cease if the temperature is reduced to the initial level (15° C). The results are based upon a non-invasive technique using infrared reflexion.

Notizen: Summary The structure of three cell types in the sensory vesicle is described: (1) The statocyte, with its intracellular statolith, is attached to the medial wall of the vesicle via delicate shaft cells. (2) Cells along the dorsal, ventral and lateral walls which contact the surface of the statocyte with long, slender cilia. These cells are presumed to be primary sensory cells. (3) Presumed secretory cells, along the rostral and dorsal walls, may have a dual function: (a) secretion of the vesicle fluid, and (b) stabilization of the wall by turgor created in characteristic intercellular cavities. The sensory vesicle in Oikopleura contains undoubtedly typical “statocyst components” adequate for a free-swimming animal, whereas the ascidian system is suggested to be a device that responds to gravitational stimuli and, together with temporary photoreceptors, aids the larva in finding optimal settling conditions.

Notizen: Summary Techniques are described for the continuous rearing of the pycnogonid Pycnogonum litorale in the laboratory. The larvae feed as ectoparasites on a polyp, Clava multicornis (Coelenterata, Hydrozoa). From hatching from the egg up to the stage with the definite body shape six moults occur. The first larval stage is the protonymphon. At the first moult it looses adhesive structures typical for this stage. After the second moult three swollen appendices become obvious at the posterior part of the larval body, indicating a region of predominant growth. At each of the four subsequent moults a new segment with one pair of definitive legs each is established by an anamery in addition to the three pairs of preliminary larval extremities. However, at the fifth moult the three pairs of larval legs and the larval proboscis vanish. A much bigger definitive proboscis is established. At the same time the animal changes its host and subsequently feeds on Metridium senile (Coelenterata, Anthozoa). This moult is the main step in the metamorphosis of the larva to the juvenile stage. It is only completed by the growth of one more pair of definitive legs at the sixth moult. The larval stages are described with special regard to the extremities, the proboscis, and fine structures of the cuticle like bristles, spinning- and other gland associated structures, and dorsal humps using scanning electron microscopy. Bristled claws and prickles are explained to have adhesive functions. Newly hatched larvae have a body length of 0.15 mm and grow up to about 1 mm after the fifth moult (change of the host). Under laboratory conditions at 15° C the larval development from hatching to the fifth moult (time point for losing larval extremities and proboscis) takes 67 days in minimum and 83 days in average..

Notizen: Summary The ultrastructure of gill epidermal cells of Diopatra neapolitana and their relationship with blood spaces are described. The existence of a basal infolding complex, related to the blood spaces, is also reported. A possible involvement of these cells in osmoregulation and ion interchange, apart from their well-known role in respiration, is suggested.

Notizen: Summary During fission the ophiuroid Ophiocomella ophiactoides splits across the disc into two halves each of which regenerates to form a complete individual. This paper describes the gross anatomy of the fission plane and the histology, ultrastructure, and mechanical properties of key structures transected during fission. Rupture of the disc integrument appears not to be facilitated by a pre-determined plane of weakness. Comparison of naturally split and artificially split animals showed that at fission a mechanism operates which restricts breakage to the interradial plane of two jaws. The interradial plane is subtended mainly by collagenous ligaments and by muscles linked to the skeletal components by basal lamina-like tendinous fibres. No fission-related adaptations could be identified in the oesophagus, circumoral nerve ring, or circumoral water vascular canal. On the basis of creep tests on isolated preparations of the disc integrument and jaw-frame and the responses of these preparations to ionic manipulation, it is suggested that their behaviour is dominated by collagenous elements that can undergo actively controlled changes in their mechanical properties. A hypothesis is presented which proposes a role for such a mechanism in the initiation and facilitation of fission.

Notizen: Summary 1. The blood supply to cephalic heat loss areas (nasal and oropharyngeal mucosa, bill, eyelids) was studied in mallards by using plastic corrosion casts. The structure and organization of the blood vessels, as well as the occurrence of arteriovenous anastomoses (AVAs), were examined by scanning electron microscopy of vascular casts and by paraffin sections. 2. Submucosal venous plexuses (cavernous tissue) are present in the nasal cavity, tongue, and lateral margins of the palate. These plexuses receive blood from post-capillary venules, but may also receive a non-nutritive component via numerous AVAs. 3. High densities of AVAs were found in the eyelids and in the tip of the bill. In the tongue and nasal mucosa, the AVAs decreased in number caudally. The reason for regional differences in the density of AVAs is discussed in relation to variation in mechanical and thermal stimulation of the tissues. 4. The connection of the different heat loss areas with the Rete ophthalmicum, which is a countercurrent heat exchanger important for brain cooling, is pointed out. The vascular pattern of the head suggests that sphincteric veins are involved in regulating the venous return from the evaporative surfaces of the nasal cavity and palate. One of these veins had, in addition to the normal circular smooth muscle fibres, a conspicuous component of longitudinally arranged, subendothelial, smooth muscle fibres.

Notizen: Summary The larval integument and juvenile girdle integument of Mopalia muscosa (Mollusca: Polyplacophora) were studied by light microscopy. Within 24 h of settlement, eight distinctive changes occur that characterize metamorphosis: loss of the functional prototroch and apical tuft, secretion of a cuticle over the mantle field followed by the secretion of calcareous shell plates and the extrusion of spicules into the cuticle, a 20% decrease in length, secretion of chitinous hairs and the incorporation of the lateral ciliated bands into the pallial grooves. Similar changes which were often not recognized as metamorphic have been reported for other species. Evidence for metamorphosis being a common developmental feature of chitons is presented.

Notizen: Summary The fine structure of the spiral ciliary receptor of three gnathostomulid species is described. Each receptor bears a single cilium — with 9+2 axoneme, basal body and accessory centriole — rolled up in an internal cavity. Spherical and annular cavities are construed as two different types of spiral ciliary receptor. Relations to presumptive photoreceptors in other lower Bilateria and considerations of possible function of these gnathostomulid receptors are discussed.

Notizen: Summary The morphology and fine structure of the vibratile anterior dorsal fin of the rockling Gaidropsarus mediterraneus are described. 60–80 fin rays project as a fringe from a reduced fin web; their lateral movement maintains the fin in almost constant rapid undulation, at a frequency of 3–4 beats per second. The fin can be laid back and with-drawn into a groove. Erector and depressor muscles, which are histologically distinct, move each ray. The fin support is modified, incorporating elastic cartilage, and enclosed in a capsule of collagenous connective tissue. The epidermis at the frontal and caudal aspect of each ray contains numerous receptor cells, over 100,000 per mm2, which have an apical microvillus and synaptic connections with nerve fibres. The recurrent facial nerve sends a major branch to the dorsal fins, which is joined by dorsal ramuli of spinal nerves. It is calculated that there are three to six million receptor cells on the vibratile fin and in the epidermis of the dorsal groove, in individuals of average size. Taste buds do not occur in the skin of the groove, contrary to a previous report, nor on the vibratile fin rays, although they are present on the prominent most anterior fin ray and elsewhere on the fins and barbels. The undulatory motion of the fin draws sea water towards and through the vibratile rays and backwards as a perceptible current. The fin constitutes a specific sensory organ, a water sampler, peculiar to this rockling and related species.

Notizen: Summary Four envelope cells are responsible for the formation of the basiconical sensilla of Calliphora. They are the thecogen, trichogen, and tormogen cells, and envelope cell 4. In early stages of development the still subepithelial sensory cilia are completely enclosed by the innermost thecogen cell. The first formation movements are initiated by a growth thrust of the hair-forming cell into the exuvial space. The sensory cilia only begin to grow into the hair anlage when the hair-forming cell has almost reached its final length. As soon as growth is completed the trichogen cell, tormogen cell, and envelope cell 4 start to excrete cuticular material. The trichogen cell forms the perforated part of the hair shaft and the stimulus-conducting system consisting of the pore tubules. The tormogen cell is responsible for the excretion of the basal non-perforated hair shaft and sheath cell 4 forms the proximal part of the socket region. The thecogen cell only begin to produce dendritic sheath material when the sensory hair is almost complete. Approximately 7–8 days after pupation the tormogen cell degenerates, having, by this time, produced about two-thirds of the sensilla cuticle. The surrounding envelope cells incorporate cell fragments of the tormogen cell. The trichogen cell continues the secretion where the tormogen cell left off. When the secretion of cuticle is finished the sheath cells begin to withdraw towards the proximal direction and to form microvilli on the apical membrane. The resulting outer receptor lymph space is bordered by envelope cell 4 and the trichogen and thecogen cells. The tormogen cell is absent in the sensilla of the imago.

Notizen: Summary In Cupiennius salei (Ctenidae), as in other spiders, the central nervous system is divided into the supraoesophageal ganglion or brain and the suboesophageal ganglia (Fig. 1). The two masses are interconnected by oesophageal connectives. The brain gives off four pairs of optic and one pair of cheliceral nerves. From the suboesophageal ganglia arise a pair of pedipalpal, four pairs of leg, and several pairs of opisthosomal nerves (Fig. 2). 1. Cell types. In the brain a total of 50900 cells were counted, in the suboesophageal ganglia 49000. They are all monopolar cells, found in the ganglion periphery and may be classified into four types: (a) Small globuli cells (nuclear diameter 6–7 μm) forming a pair of compact masses in the protocerebrum (Fig. 10b); (b) Small and numerous cells (cell diameter 12–20 μm) with processes forming the bulk of the neuropil in the brain and suboesophageal ganglia; (c) Neurosecretory cells (cell diameter ca. 45 μm) in the brain and suboesophageal ganglia; (d) Large motor and interneurons (cell daimeter 40–112 μm), mostly in the suboesophageal ganglia (Figs. 10a and c). 2. Suboesophageal mass. The cell bodies form a sheet of one to several cell layers on the ventral side of each ganglion and are arranged in groups. Three such groups were identified as motor neurons, four as interneurons. At the dorsal, dorso-lateral, and mid-central parts of the ganglion there are no cell somata. The fibre bundles arising from them form identifiable transverse commissural pathways (Fig. 9b). They form the fibrous mass in the central part of the suboesophageal mass. Neuropil is well-formed in association with the sensory terminations of all major nerves (Fig. 9a). As these proceed centrally they break up into five major sensory tracts forming five layers one above the other. There are six pairs of additional major longitudinal tracts arranged at different levels dorsoventrally (Fig. 8). They ascend into the brain through the oesophageal connectives and terminate mostly in the mushroom bodies and partly in the central body. 3. Protocerebrum. Fine processes of the globuli cells form the most important neuropil mass in the fibrous core, called the mushroom bodies. These consist of well developed glomeruli, hafts, and bridge which are interconnected with the optic masses of the lateral eyes and most fibre tracts from the brain and suboesophageal mass (Fig. 7). The median eye nerves form a small optic lamella and optic ganglia, connected to the central body through an optic tract. Each posterior median and posterior lateral eye nerve ends in large optic lamellae (Fig. 13a). These are connected through chiasmata to a large optic mass where fibres from globuli cells form conspicuous glomeruli. There are 10–12 large fibres (diameter 9 μm) of unknown origin on each side, terminating in the optic lambella of the posterior lateral eye. The central body, another neuropil mass (Fig. 13b) in the protocerebrum, is well developed in Cupiennius and located transversely in its postero-dorsal region (Fig. 10d). It consists of two layers and is interconnected with optic masses of the median and lateral eyes through optic tracts. Fibre tracts from the brain and suboesophageal mass join the central body.

Notizen: Summary The bursa of Dugesia tigrina is located between pharynx and penis and is suspended in a network of muscle fibers. Two cell types are present in the bursa: small outer cells which likely represent replacement cells and tall inner cells. During copulation seminal material, consisting of secretion products, fibrillar and tubular material, and small clusters of spermatozoa, is injected through the bursa canal into the bursa. During the 48 h post-copulatory period the seminal material is absorbed by the inner cells. Phagocytosis of the seminal material is facilitated by broad apical cytoplasm and modified distal cell membranes. Phagocytosed spermatozoa are enclosed in vaculoes and morphologic breakdown occurs as early as 4 h after copulation. Fibrillar and tubular material is phagocytosed directly into the apical, organelle-free cytoplasm without vacuole formation. The bursa canal is ciliated and the distal cell ends are studded with ultrarhabdites. These are also present in the epithelial cells of the female antrum. Antrum epithelial cells furthermore display apical organelle-free cell areas. Numerous glands penetrate through the antrum wall.

Notizen: Zusammenfassung An 476 Käfern der Art Acanthocinus aedilis L. wurden Messungen durchgeführt, um die verschiedenen Allometrien und Korrelationen der einzelnen Körperteile zu prüfen. Damit sollte versucht wurden, einen Einblick in die Vielfalt der Faktoren, die einen Einfluß auf die Körperproportionierung haben, zu gewinnen. 1. Fast alle Körperteile nehmen bei dem Zimmermannsbock mit steigender absoluter Körpergröße positiv allometrisch zu (Ausnahmen: Thorax- und Mittelbeinlänge bei den Weibchen). Die Allometriekoeffizienten wurden graphisch bestimmt, sie sind bei den Männchen größer als bei den Weibchen (nur der Hinterbeinkoeffizient ist gleich). 2. Auf Grunt der unterschiedlichen Organgrößenzunahme konnte in beiden Geschlechtern ein besonders starkes Wachstumszentrum in den Fühlern, mit einem Maximum terminal im II. Glied, nachgewiesen werden. Weitere wesentlich schwächere Wachstumszentren liegen in der Tibia jeder Extremität. 3. Von dem durch einen besonders hohen Allometriekoeffizienten gekennzeichneten Wachstumszentrum in den Fühlern aus nimmt die Stärke der Allometrien zu den morphologisch hinten gelegenen Organen kontinuierlich, gradientenförmig ab. Außer diesem Hauptgradienten entlang des Körpers, der bei den Männchen stärker in Erscheinung tritt als bei den Weibchen, konnte auch in den Fühlern von distal nach proximal ein ähnliches Gradientengefälle nachgewiesen werden. 4. Bei genauerer Analyse der Länge der ganzen Extremitäten und ihrer Glieder zeigte rich, daß hier verschiedene Korrelationen ineinandergreifen. 5. Neben diesen allgemein gültigen Korrelationen treten im einzelnen Unregelmäßigkeiten auf; die wahrscheinlich modifikatorisch bedingt sind 6. Die besonders starke positive Allometrie der männlichen Fühler zeigt bei den größten Individuen eine auffallende Depression, die sich durch Materialkompensation erkldren läßt. 7. Verschiedene Allometriekoeffizieten von Fühlergliedern erfahren — sobald die Antennen eine bestimmte Größe überschreiten — eine Änderung. Es wird versucht, dies durch unterschiedlichen Transportweg der Stoffe zu erklären, die zum Aufbau der imaginalen Organe an den betreffenden Stellen benötigt werden. 8. Die Fühler und Beine der in Südtirol gefangenen Männchen sowie die Fühler der dort gefundenen Weibchen sind bei gleicher Körpergröße deutlich kürzer als die entsprechenden Organe nordwestdeutscher Tiere. Es muß angenommen werden, daß für diese Unterschiede Temperatureinflüsse während der Entwicklung verantwortlich sind. 9. Die zum Teil starken individuellen Abweichungen von den allgemein gültigen Allometrien verlaufen bei Fühlern und Extremitäten weitgehend parallel. Dies kann als Stütze für den Temperatureinfluß auf die Körperproportionierung angesehen werden, vomit sich ein Faktor anbietet, der auf physiologischer Grundlage alle individuellen Allometrieabweichungen erklärbar macht. Durch die vorliegenden metrischen Untersuchungen an Acanthocinus aedilis wurden die Allometrien, die Lage der Wachstumszentren und-gradienten bestimmt, die im allgemeinen als genetisch festgelegt anzusehen sind. Diese Fixierung gibt allerdings nur einen Rahmen, innerhalb dessen eine weitgehende modifikatorische Variabilität, deren Ursachen diskutiert werden, möglich ist.

Notizen: Zusammenfassung 1. Die Symbiose von Stictococcus diversiseta unterscheidet rich weitgehend von der kürzlich von Sti. sjoestedti beschriebenen. 2. Die Symbionten stellen hefeähnliche Organismen dar, die in den Körper des Wirtes allseitig durchsetzenden Mycetocyten leben. 3. Die Übertragung ist eine sehr eigentümliche. Die Hefen treten zunächst in eine dünne zellige Umhüllung der Ovariole über and gelangen von hier vor allem in den Bereich der Nährzellen and des an sie anschließenden Teiles des Follikels; nur vereinzelt erscheinen sie aueh zwischen den ersten Blastomeren. 4. Die Entwicklung der aueh hier sehr klein and dotterfrei bleibenden Eier verläuft nicht minder seltsam als bei Sti. sjoestedti, bewegt sich aber in ganz anderen Bahnen. Die Furchung ist wieder eine totale and führt zu einer diesmal symbiontenfreien Morula. Gleichzeitig verkürzt and verdickt sich die Ovariole, die anfangs dünne sekundäre Umhüllung nimmt beträchtlich an Dicke zu, die Follikelzellen runden sich ab, geben das epitheliale Gefüge auf and wandern nach der Peripherie. Die gleiche Verlagerung machen die damit wieder freigewordenen Symbionten durch. Durch eine Art Delamination grenzt rich rund um die Morula eine Zelllage ab, welche unter gleichzeitiger beträchtlicher Flüssigkeitsaufnahme des Embryos immer weiter von den zentralen Zellen abgehoben wird. Sie stellt die Anlage der Serosa dar. In dem so hinter ihr entstehenden Raum tauchen schon sehr friih einzelne Dotterkerne auf. Die restlichen Elemente der Morula ordnen sich erst zu einer Rosette, dann unter leb-hafter Vermehrung der Zellen zu einem Schlauch, der sich an die Wand der Serosa heftet and sich damit als die Anlage des Keimstreifs and des Amnions bekundet. 5. Inzwischen ist die innerste Zellage der sehr ansehnlichen sekundären Hülle zu locker liegenden Riesenzellen herangewachsen. Diese nehmen die freigewordenen Symbionten auf and befördern sie an das Hinterende des Embryos. Dorthin gleiten auch die abgerundeten Follikelzellen, die schließlich ebenfalls von den Riesenzellen aufgenommen werden. Wenn der auch hier, wie bei sjoestedti, von vorne nach hinten auswachsende, sich S-förmig krümmende Keimstreif zwar schon weit entwickelt ist, aber noch vor der Anlage der Extremitäten steht, werden die Symbionten wieder von den Riesenzellen entlassen, passieren die hintersten Zellen der Serosa and treten so endlich in den Embryo über, wo sich ihnen Dotterkerne zugesellen und damit die ersten Mycetocyten entstehen. Die ehemaligen Follikelzellen und die Riesenzellen gehen außerhalb des Embryos zugrunde. 6. Bei einem TO der Ovariolen unterbleibt die Infektion und diese sterilen Embryonen entwickeln sich wie bei sjoestedti zu männlichen Tieren. Die Follikelzellen kugeln sich auch in diesen Fällen ab, die Riesenzellen differenzieren sich ebenfalls, aber es kommt nicht zur Aufnahme der ersteren in die letzteren. Die Follikelzellen fließen vielmehr zu größeren and kleineren Syncytien zusammen and degenerieren wie die Riesenzellen and die Reste der Ndhrzellen im Raume zwischen Embryo and sekundärer Hülle. Wie bei sjoestedti ist der Verlust der Symbiose auf die schon auf dem ersten Larvenstadium vorhandene völlige Rückbildung der Mundteile zurückzuführen. Die funktionslos bleibenden Riesenzellen stellen eine Erinnerung an die Zeit des Symbiontenbesitzes dar. 7. Die tiefgreifenden Unterschiede zwischen den beiden so nahe verwandten Arten werden eingehend erörtert and die Frühentwicklung mit der der Chalcididier and Proctotrupiden, den einzigen Insekten, bei denen sonst eine totale Furchung vorkommt, verglichen. Es wird wahrscheinlich gemacht, daß die Verfahren von Sti. diversiseta eine ähnliche Symbiose wie sjoestedti aufwiesen, sie aber im Anschluß an die zusätzliche Aufnahme von Hefen, die sich mit den Stammsymbionten nicht vertrugen, verloren haben. 8. Während bei Sti. sjoestedti das Zustandekommen bzw. Ausbleiben der Eünfektion davon abhängt, ob sich in der unmittelbaren Nachbarschaft der Ovariole Mycetocyten befinden Oder nicht, scheinen bei diversiseta andere, morphologisch zunächst nicht faßbare Momente über Infektion oder Nichtinfektion des Follikels and damit des späteren Invaginationsstadiums zu entscheiden.