ALBERT

Description: The nervous system in the tentacles of the sea anemones Tealia felina, Anemonia sulcata, Metridium senile and Cerianthus membranaceus was studied using light microscopic and electron microscopic techniques. \nBecause of the small dimensions of the nerve cells (6\xe2\x80\x947 \xc2\xb5m) and of the neurites (diameter 〈 1 \xc2\xb5m) satisfactory information could not be obtained using conventional histological techniques. \nElectron microscopic investigation showed that the nervous system can be divided into three parts: the plexus round the mesogloea, a nervous system between the muscles (obviously connected with the plexus) and sensory cells in the outer layer of the tentacle connected to the plexus by nerve fibres. The latter nerve cells with their fibres are arranged radially in the tentacle ectodermis. These are the only sensory cells discovered in the tentacles of the sea anemones. \nIn these radial neurites and in a number of neurites in the plexus, dense core granules are found. In the nervous system between the muscles and in a number of neurites in the plexus, opaque granules are found. Neurites containing dense core as well as opaque granules were never observed. Only in the radial neurites and in the plexus a yellow F(ormol) I(nduced) F(luorescence) was observed. Analysis of the emission spectrum showed that the F.I.F. had developed from a catecholamine (most probably noradrenalin). Therefore the dense core granules contain a catecholamine. \nOn the basis of morphological similarity, the neurites containing opaque granules may be identified as purinergic as proposed by Burnstock (1972), since the innervation of the muscles in the sea anemones very much resembles the innervation of smooth muscles in vertebrates. \nSynapses as described by a.o. Westfall (1973a) could not be demonstrated. However, desmosome-like structures were found between the epithelial cells and between the muscles, so that a non-neural conduction (c.q. myoepithelial conduction) is probable. This myoepithelial conduction may explain the presence of a \xe2\x80\x9csecond nervous system\xe2\x80\x9d postulated by Bullock & Horridge (1965) which is supposed to be a slowconductive system. A morphological indication for a \xe2\x80\x9csecond nervous system\xe2\x80\x9d has never been found. \nThe two transmitter substances mentioned (no indication was found for the presence of GABA and acetylcholine), i.e. a catecholamine, most probably noradrenalin, and a purine derivate, both have an excitatory function. The possible role of glutamate as an inhibitor has been discussed. Glutamate acts as a possible inhibitor, since it is released from contracting muscles and inhibits the contraction via an unknown mechanism. \nHydra was investigated and the findings were discussed in relation to the existing literature. Only the existence of synapses was discrepant, since these structures could not be demonstrated. \nRegarding the possible transmitters a catecholamine could be demonstrated with the F.I.F. method. A purinergic muscle innervation is possible in view of our experience with sea anemones.

Description: The study of some newly collected material from the West Indies may justify a fourth paper on Caribbean Tenebrionidae in these \xe2\x80\x9cStudies\xe2\x80\x9d. Thanks to dr. P. WAGENAAR HUMMELINCK\xe2\x80\x99S collecting work, the Tenebrionid fauna of the Antilles and the adjacent South American mainland shores may be considered to be pretty well known \xe2\x80\x94 at least as far as the Melasomes are concerned. Thus zoogeographical conclusions \xe2\x80\x94 though not differing essentially from those published in 1962 \xe2\x80\x94 appear to have a rather solid basis. Unfortunately much less is known about planticolous Tenebrionids, which anyhow are relatively less interesting for zoogeographical purposes, than the geophilous ones.\nWe also had the privilege of consulting the collections of the I.N.R.A. at Guadeloupe (see MARCUZZI & D\xe2\x80\x99AGUILAR 1971) which considerably increased our knowledge of the Tenebrionid fauna of that and neighbouring islands. Several specimens on hand at the Institute of Marine Biology, Mayag\xc3\xbcez, proved extremely useful for obtaining a better knowledge of the Tenebrionid fauna of the old, sedimentary island of Puerto Rico. In a few single cases material from other sources (British Museum, Museum G. Frey and the private collection of the author) has been used.

Description: Cercariae have been collected and studied from two sampling areas, situated at a distance of about 5 km of one another, South-East of Amsterdam.\nThirteen species are mentioned in this paper, seven of which are reported from the Netherlands for the first time. Two species are described in detail: an echinostome cercaria tentatively identified as Cercaria deficipinnata Khan, 1960, and a new xiphidiocercaria belonging to the group \xe2\x80\x9carmatae\xe2\x80\x9d, named Cercaria otiosa n. sp.\nThe cercarial fauna in the two sampling areas is compared, and possible causes of differences are briefly discussed.

Description: A primitive freshwater planarian, Eviella hynesae gen. et sp. nov. is described from Australia. It is characterized by its lack of eyes and pigment, possession of caudally branched oviducts, and fully fused testes. Although a primary bursa is absent, its function being taken over by the modified female genital canal, the female copulatory system is posterior to the male system. Despite this maricolan feature, and other similarities with primitive southern hemisphere freshwater planarians that have been classified in the Maricola, the present species is placed in the family Dugesiidae of the Paludicola. Evidence from its sensory organs suggests that it belongs on the main evolutionary line from which the majority of Australasian freshwater planarians have been derived.

Description: Every new mammal or bird in the Amsterdam zoo, without exception, is kept in quarantaine for some weeks and until necessary standard checks are done. The number of mammals in the collection during the period 1967-1973 varied between 729 and 858 belonging to 172 to 208 species. In birds these figures were 1571 and 1803 specimens of 391 to 520 species (table I). The average percentage of deaths in mammals was 12.4% (table II) and in birds 13% (table III).\nThe causes of death (tables IV and V) are arranged under 15 headings for mammals and under 18 for birds; both numbers and percentages are given. During 1967, 1968, and 1969 there were many cases of Yersinia pseudotuberculosis in the nocturnal house. The troubles only stopped after vaccination of all animals already present in the house and of the new ones before housing them. Cases of non-identified infections in psittacine birds (53 victims) and penguins (19 victims) are provided. The same holds true for a skin disease in apes and diabetes in ruminants. A rather detailed report is given on cowpox in indian elephants in 1973. The three females of different age were affected; the male stayed free. All animals recovered after periods ranging from 17 to 57 days. One elephant had serious foot troubles in the same period, the most serious at the left forefoot. It took about 6 weeks before all animals recovered completely.\nThe survival rate of newborn mammals fluctuated between 59% and 66%, at a number of births fluctuating from 164 to 249 a year (table VI). The low rate of 56% for wild ruminants could be raised to 67% by feeding extra minerals to pregnant and nursing females. In birds hatched (table VII) the survival rates varied between 49% and 75%. The low figure is caused by the very bad results with ducks (in 1969 only 25% survival). By changing the accomodation we brought the figure for ducks up to 83% at the end of the period reported upon.

Description: In the Colorado Beetle, the terminal filament cells resemble the epidermal cells which connect muscle cells with the cuticle, the so-called tendon cells. They contain many microtubules which have projections interconnecting them. The microtubules are also connected by these projections to desmosomes.\nThe tunica propria is a basement membrane-like layer of low elasticity. It separates the terminal filament from the germarium. The outer ovariole sheath is a muscle sheath which is continuous with the muscle sheath around the oviducts. The whole muscle sheath consists of a monolayer network. Sarcolemmal invaginations at the I band and at the Z line probably form part of one T system. The cuticle of the common oviduct has scales with long caudally directed spines.\nThe rostral attachment of the muscle sheath corresponds to the existing descriptions of tendon cells. The attachment of the muscle sheath to the cuticle of the common oviduct is different.

Description: The sedentary ciliate fauna living on the body surface of Gammarus tigrinus and G. pulex from Dutch freshwater habitats has been investigated. Fourty-seven ciliate species are found, of which 43 belong to the order Peritrichida, suborder Sessilina, 3 belong to the order Suctorida and 1 belongs to the order Chonotrichida. Two new species in the genera Intranstylum and Pseudocarchesium are described.\nIt appears that there is a seasonal variation in the number of epizoic ciliates as well as in species composition. In general, the species with a contractile stalk are found on external, often fast-moving, body parts. Species with a noncontractile stalk seem to prefer more quiet and sheltered positions. After ecdysis there is a succession of the genera Epistylis and Zoothamnium, the latter becoming dominant on older exoskeletons.

Description: Prof. Dr. Gerard Barendrecht was born on the 9th of October 1906 in Hilversum. After his final examinations in Kampen in 1923 there came a year of private studies of Greek and Latin. These formative years resulted in a continuing interest in the classical writers which he still reads as a relaxation from more strenuous tasks. On the other hand, the polders in the neighbourhood of Kampen gave the inspiration to the writing of the \xe2\x80\x9cGlorie van ons polderland\xe2\x80\x9d (\xe2\x80\x9cGlory of our polderland\xe2\x80\x9d).\nIn 1924 he entered the University of Amsterdam as a student in biology where he took his \xe2\x80\x9cdoctoraal examen\xe2\x80\x9d (master\xe2\x80\x99s degree) in 1929. His doctor\xe2\x80\x99s degree dates from the 20th of January 1932. His thesis \xe2\x80\x9cDie Corpora pedunculata bei den Gattungen Bombus und Psithyrus\xe2\x80\x9d is an elegant synthesis of his former work in the Dutch Central Institute of Brain Research as an adjunct-assistent to Prof. Dr. C. U. Ari\xc3\xabns Kappers and his work with his promotor, the entomologist Prof. Dr. J. C. H. de Meijere.

Description: Regenerative capability of Plexaura flexuosa is investigated in experiments which simulate the injuries caused by predation of the ovulid snail Cyphoma gibbosum: partial or total removal of the coenenchyme from the axial skeleton.\nRegenerative growth of the coenenchyme is primarily induced by the possibility of linear extension of the axial epithelium; settlement of fleshy algae or e.g. Millepora (firecoral) on the axial skeleton inhibits the recovery of the coenenchyme. Coenenchyme growth is accompanied by evagination of the polyp cavity wall and by increased mesoglea production. The cellular basis for regeneration lies in the migration capability and morphogenetic plasticity of at least two cell types of the coenenchyme epidermis: interstitial cells and \xe2\x80\x9ctransitional\xe2\x80\x9d cells.\nRepeated removal of re-grown coenenchyme causes a decrease of the polyp density followed by the formation of new polyps. These are formed by an extra-tentacular budding mechanism which has its primordia in the epidermis of the coenenchyme.

Description: The distribution of the larvae of Eylais discreta on the abdominal tergites of the host species Sigara striata, S. falleni and Cymatia coleoptrata is examined.\nOn S. striata and S. falleni the segments 3 and 4, on C. coleoptrata the segments 2 and 3 are successively preferred. There is but little influence of multiple infestations on this distribution.\nThe growth rate on the various tergites of S. striata is similar, while on C. coleoptrata a possible difference could not be proved statistically. The larvae of E. discreta generally hibernate on the host; during this phase there is little growth; not until March-April they start growing faster. The larvae on C. coleoptrata are retarded in growth compared to those on S. striata.\nThe larvae on S. falleni do not show any increase in size; this water bug species is immune to infestation by various Hydrachnellae.