ALBERT

Beschreibung: Oogenesis in four commercial Caribbean sponge species, Hippospongia lachne, Spongia barbara, S. cheiris and S. graminea, was studied using light and transmission electron microscopy. Eggs and embryos develop asynchronously in localized endosomal nurseries of these viviparous and gonochoristic species. Statistical analyses of specific morphological characteristics of reproductive elements have unequivocally identified four specific stages in the process of oogenesis. Oogonia undergo mitotic division to produce primary oocytes. Meiotic division occurs producing secondary oocytes which are fertilized before zygotes undergo major growth by phagocytosis and the transfer of nutrients through cytoplasmic bridges. During cleavage of the zygote, umbilici form between embryos and nurse cell layers and these function in the transfer of symbiotic bacteria and other mesohyl substances from the maternal parent to the embryo. These symbionts were observed dispersed between blastomeres of all young and maturing embryos and between internal cells of cytodifferentiated parenchymella larvae. Extracellular transfer of symbiotic bacteria from maternal tissues to developing embryos has not been reported in any other viviparous invertebrate.

Beschreibung: Before 1985, Martialia hyadesi (Cephalopoda: Ommastrephidae) in the Pacific Ocean was known only from the Eltanin Fracture Zone and Macquarie Island. A joint Japan‐New Zealand squid survey around New Zealand captured many immature ommastrephid squids. Gel electrophoresis confirmed the presence of immature M. hyadesi. Aspects of the external morphology are described. The distinctive tentacle club was evident in the smallest specimen examined, 19 mm dorsal mantle length (ML). Arm trabeculae were first evident in specimens of 40–50 mm ML. Immature squid were distributed around and southward of the Subtropical Convergence Zone. The presence of very small squid (〈 10 mm ML) indicated spawning on or near the Auckland Island Shelf.

Beschreibung: Records of 158 observations of cephalopods from submersibles, primarily the Johnson Sea-Link, have been compiled through collaboration with several investigators. These observations include 118 videotape sequences, 58 collected specimens, and numerous shipboard photographs of live animals. At least 33 species have been observed to date; a few species have been observed repeatedly and could be good subjects for directed studies. The methods developed for in situ observation and subsequent collection of specimens with little or no damage allow descriptions of behavior, morphology, physiology, and distribution that are not possible with other methods of collecting.

Beschreibung: Eleven species of paralarvae belonging to the Chiroteuthidae and related families are described from Hawaiian waters. The doratopsis stage is shown to be a diagnostic feature of the family Chiroteuthidae. This family, as now defined, includes the genera Chiroteuthis, Asperoteuthis, Grimalditeuthis and Planktoteuthis. Doratopsis sagitta, Valbyteuthis, Tankaia, Echinoteuthis and Enoptroteuthis spinicauda are placed as junior synonyms of Grimalditeuthis bonplandi, Planktoteuthis, Chiroteuthis, Mastigoteuthis and Lepidoteuthis grimaldii respectively. An unknown type of paralarva referred to as “big-fin” is described. Members of the “chiroteuthid lineage” which apparently includes the Chiroteuthidae, Mastigoteuthidae, Joubiniteuthidae, Batoteuthidae, Promachoteuthidae and “big-fin” may all have secondarily derived tentacular clubs.

Beschreibung: The presence of Stoloteuthis leucoptera in the Mediterranean is recorded on the basis of three specimens, including an adult male, caught by IKMT and by commercial otter-trawl in the Ligurian Sea. The hypothesis of a recent immigration is discussed. The list of Mediterranean cephalopods (Mangold Wirz, 1963; Torchio, 1968; Bello, 1986; Mangold & Boletzsky, 1987) includes the Sepiolidae of the subfamily Heteroteuthinae, whose members are supposed to be pelagic throughout their life cycle. Mangold Wirz (1963) recognizes in the Mediterranean fauna the unique species Heteroteuthis dispar, the other authors include H. atlantis Voss, which Voss himself (1955) reported at Messina. To this group may now be added Stoloteuthis leucoptera (Verrill, 1878) a species until now recorded in limited Atlantic areas. Verrill (1881) wrote “This species is an exceedingly beautiful one, when living, owing to the elegance and brilliancy of its colours and the gracefulness of its movements. In swimming it moves its fins in a manner analogous to the motion of the wings of a butterfly.”

Beschreibung: Sexual reproductive cycles of a Florida, U.S.A., population of four Caribbean commercial sponge species, Hippospongia lachne, Spongia barbara, S. cheiris and S. graminea, were determined by analysis of tissue samples collected over a three-year period. Spermatogenesis in these species was studied using light and transmission electron microscopy. The production of male gametes occurs in cysts within the endosomal tissue of mature specimens. Reproductive elements within an individual cyst develop synchronously while development between cysts is asynchronous. All available evidence suggests that these species are dioecious. Spermatogonia differentiate directly from choanocytes in situ. All cells of the chamber lose their collars and flagella and undergo mitosis to produce primary spermatocytes, each possessing a single flagellum. The ratio of nucleus to cell diameter in these cells is almost double that of choanocytes. Circumstantial evidence suggests that primary spermatocytes undergo meiosis to produce four spermatids, but confirmational chromatid linkage figures are still lacking. The mature spermatozoa lack both intermediate segments and acrosomes. Male gametes displayed a bright yellow-white autofluorescence when excited with blue light (460–485 nm).

Beschreibung: Squid on their spawning grounds feed mainly at night when they are more dispersed. In all, 28,5 per cent of squid sampled at night had food in their stomachs, whereas only 6,7 per cent of those collected by day had food. Most stomachs contained only a single prey species (90,8% of those analysed). Teleosts dominated the prey of squid collected at night (58%M), followed by crustaceans (25%), polychaetes (9%) and cephalopods (3%). By day the prey was dominated by cephalopods (61%), followed by teleosts (20%), crustaceans (14%) and polychaetes (2%). Bregmaceros sp. was the most frequently identified teleost, Loligo vulgaris reynaudii (cannibalism) the dominant cephalopod, ?Betaeus sp. (Alpheidae; pieces of coral were also found) the commonest crustacean and Nereis sp. the commonest polychaete. There were seasonal differences in the diet too: squid caught during summer seemed to have similar proportions of the four main prey components. Also, the incidence of feeding was higher than in winter. There were, however, no significant differences in stomach mass expressed as a percentage of body mass between day and night nor between season nor between sexes. The average stomach mass of all samples was 0,6 per cent of body mass, less than on the feeding grounds, where it is generally about 2 per cent.

Beschreibung: In the coastal waters between Cabo Frio, Rio de Janeiro State (Lat. 23°S) and Chui, Rio Grande do Sui State (Lat. 34°S), more than 30 species of cephalopods occur in the different marine environments. Temperate benthic octopuses of low fecundity, bearing large eggs, are restricted to the cold bottom waters of the outer shelf and the slope, in contrast to species of tropical origin, which occupy the more diverse shallow water habitats, principally along the Rio de Janeiro coast. Cosmopolitan warm-water octupuses with high fecundity, like Scaeurgus unicirrhus and Octopus vulgaris, are found along the entire area because the transport of pelagic juveniles is favored by the warm, southward flowing superficial Brazil Current. All three families of epipelagic octopuses are represented. The neritic squid fauna includes only five myopsid squids, four of them of tropical origin. At the upper slope Illex argentinus is dominant and several mesopelagic and bathipelagic oegopsids, widely distributed in tropical and temperate Atlantic Ocean waters, also occur. The absence of endemic species indicates the transitional character of the fauna between the Caribbean and the Patagonian regions.

Beschreibung: Based on sequential growth stages of Moroteuthis robusta, M. japonica and M. pacifica are synonymous with M. robusta, and smaller stages are bridged to the Onykia “carribaea” species complex. Within the family Onychoteuthidae, the genus Onykia has in common with the genus Moroteuthis the absence of both visceral photophores and dorsal nuchal folds. Young Moroteuthis have a smooth mantle surface with a distinct iridescence, a small number of marginal suckers on the tentacular club and an indistinct cartilageous cap on the endocone. While, large Onykia develop rhomboidal fins, an inverted Y-shaped cartilageous ridge in the funnel groove, and a reduced number of marginal suckers on the club, all of which characterize Moroteuthis. Close examination of a series of O. “carribaea” specimens reveals that the species is not monospecific, but contains more than one species. It is thus suggested that the genus Onykia, therefore, appears to represent juvenile stages of the genus Moroteuthis.

Beschreibung: Force chain buckling, leading to unjamming and shear banding, is examined quantitatively via a discrete element analysis of a two-dimensional, densely-packed, cohesionless granular assembly subject to quasistatic, boundary-driven biaxial compression. A range of properties associated with the confined buckling of force chains has been established, including: degree of buckling, buckling modes, spatial and strain evolution distributions, and relative contributions to non-affine deformation, dilatation and decrease in macroscopic shear strength and potential energy. Consecutive cycles of unjamming–jamming events, akin to slip–stick events arising in other granular systems, characterize the strain-softening regime and the shear band evolution. Peaks in the dissipation rate, kinetic energy and local non-affine strain are strongly correlated: the largest peaks coincide with each unjamming event that is evident in the concurrent drops in the macroscopic shear stress and potential energy. Unjamming nucleates from the buckling of a few force chains within a small region inside the band. A specific mode of force chain buckling, prevalent in and confined to the shear band, leads to above-average levels of local non-affine strain and release of potential energy during unjamming. Ongoing studies of this and other buckling modes from a structural stability standpoint serve as the basis for the formulation of internal variables and associated evolution laws, central to the development of thermomicromechanical constitutive theory for granular materials.