ALBERT

Beschreibung: Starvation resulting from failure to feed successfully after absorption of the yolk reserves has been proposed to be a major source of pre-recruitment mortality in squids. To test this hypothesis, methods must be developed to determine whether paralarvae have fed successfully at sea. When paralarvae are stained with Alcian Blue and then cleared with trypsin, the entire digestive tract can be examined intact for the presence of food. This method was used for Abralia trigonura and Sthenoteuthis oualaniensis paralarvae from Hawaiian waters. Approximately 9% of the former and 16% of the latter contained recognizable food material, mostly crustacean fragments. Food was found in the stomach, caecum, and intestine. The smallest specimen of A. trigonura with recognizable food in its digestive tract was 2.2 mm dorsal mantle length (DML), while for S. oualaniensis the smallest was 5.2 mm DML. The method is also useful for visualizing the ontogeny of the digestive-tract organs, beaks and radula, and other organs such as statocysts and eyes.

Beschreibung: Inadequate identification of octopus age classes has severely limited field studies of their biology. Four predictions are made to differentiate males at the plateau of growth that precedes senescence, i.e., mature males, from immature males. Compared to immature males, mature males are predicted to be 1) more mobile because their reproductive fitness depends on the number of receptive females they encounter; 2) more often injured, due either to increased mobility or decreased regeneration capacity; 3) more attractive as mates due to their maturity; and 4) mature males, overall, are predicted to be larger due to their advanced age. An intertidal population of Octopus digueti, sampled for 1 year, provided data to test the hypothesis that males with a few conspicuously enlarged suckers represent a mature age class as characterized above. As a group, males of O. digueti with enlarged suckers met these expectations; therefore, the presence of enlarged suckers is concluded to accurately indicate male maturity. I suggest enlarged suckers act as chemoreceptors of chemical cues released by receptive females and thus may contribute directly to male fitness.

Beschreibung: Samples of Loligo gahi (D'Orbigny) were collected from commercial fishing vessels in the Falkland Islands Interim Conservation and Management Zone (FICZ) between March and October 1987, and from the R/V Wieczno during a survey in August 1988. Samples were divided according to the two fishing seasons (February to July; August to October) and the samples from the scientific survey were pooled with those of the second commercial fishing season. L. gahi were aged using putative daily growth increments within the statoliths. There was indirect evidence that growth increments in the statolith were laid down at the rate of one per day. The maximum life span of the males was a little over 1 year and was approximately 1 year in females. Back-calculation ofthe month of hatching reveals the presence of two spawning groups within the FICZ population which give rise to the two fishing seasons. Growth rates were calculated for both sexes from both seasons. There was considerable individual variation in growth rate in squid from both seasons and there was more scatter in the data from first season samples taken from the commercial fishery alone. Log-linear growth models give the best fit to the data combining the fishery and scientific survey samples from the second season. Very low or apparent negative growth exhibited by squid sampled during the first season may be due to bias because the commercial fishery samples a narrow depth range. Migration of schools of squid of similar size through the narrow depth range in which the fishery operates probably yields samples that are size selected. Care should be taken in modelling squid growth where migratory effects may bias the data.

Beschreibung: Cephalopods, including octopus, cuttlefish, and squid, are a major component in the marine biomass. Due to high behavioral diversity among species, uncertainty exists concerning the general applicability of sampling and capture techniques. This factor impacts on understanding of the overall abundance and status of stocks. In addition to accelerated exploitation of cephalopods by international fisheries countries, cephalopods represent a major prey component in the diets of other marine species. In the Southern Ocean alone, it is estimated that the consumption of cephalopods by seabirds, whales and seals may reach 34 million tons annually. On a worldwide basis, the total natural predation on cephalopods probably exceeds 100 million tons, more than the total annual harvest of aquatic species by humans. Scientists and fisheries managers are not able to accurately measure cephalopod stocks under direct exploitation. Yet the relatively few species being exploited comprise only a fraction of available worldwide resources. Some of the traditional capture techniques are discussed with an indication of their effectiveness; possible options and access to new or latent methods also are noted.

Beschreibung: Professor Gilbert L. Voss served the leading role in American cephalopod research for nearly 40 years. He drew attention to the importance of cephalopods in marine ecosystems and as fisheries resources. Through his research and that of his students he significantly advanced the knowledge of cephalopod systematics, distribution and biology. An insight into Gil Voss' ideas and attitudes concerning cephalopod research and teaching is given. Voss's broad interests are indicated in his bibliography of over 210 diverse published items, including 73 book reviews, 16 editorials, and 124 research papers on cephalopods, fishes, crustaceans, botany, zoogeography, history of oceanography, anthropology, fisheries, and marine and deepsea biology. He authored or co-authored descriptions of two new families or subfamilies, 6 new genera and more than 65 new species or subspecies.

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: 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: Cephalopods are a common but not abundant element of the micronekton of the eastern Gulf of Mexico, an area hydrographically and biologically similar to low latitude oligotrophic oceans throughout the world. Forty seven species were identified from Tucker trawl collections in the vicinity of 27°N, 86°W, with seven new records for the Gulf. All species have been recorded from the Atlantic and 69% are pan-oceanic at low latitudes. The Teuthoidea were the largest fraction of the catch, particularly species of the families Enoploteuthidae and Cranchiidae. All but three species occurred in the epipelagic zone at night and diel vertical migration is suggested for many of the population. Closing trawl data indicate that most of the cephalopod population occurs shallower than 200 m at night and centers at 100 to 400 m during the day. Populations of several of the abundant, smaller species were greatest in July but this could not be linked, on the basis of size measurements, to recruitment of juveniles to the population. Diet analysis indicates that micronektonic cephalopods are crustacean feeders as juveniles, but rely more on fish as they mature (〉4 cm mantle length). Some cannibalism is apparent. Cranchiids contained relatively little food which might result from a relatively inactive life strategy. The latter is suggested by rather flaccid musculature in comparison to other teuthoids. The copepod genus Pleuromamma is highly selected for by a number of species, perhaps a function of the strong bioluminescent signal produced by members of this genus. Cluster analysis revealed several feeding guilds among the abundant species, though intracluster diets usually exhibited strong overlap. Given the relatively low abundance levels of cephalopods (50–70·103km−2; 0–1,000 m), trophic competition may stem primarily from more abundant (〉10×) micronektonic groups such as midwater fishes and shrimps than from other cephalopods.

Beschreibung: Geographical variation in the morphological characters of Australian Rossiinae were examined using principal component analysis (PCA), multivariate analysis of variance (MANOVA), discriminant function analysis (DFA), analysis of variance (ANOVA) and latitudinal and longitudinal regression analyses. The results show that morphological differences occur between populations of Rossia from the North West Shelf (W.A.) and populations from eastern and southern Australia. Evidence from these analyses suggest that these two populations are genetically distinct, the North West Shelf specimens belonging to a possible new species, described as R. sp. 1, the eastern and southern Australian specimens identified as R. australis Berry, 1918 and redescribed on the basis of new material. That all the latter specimens belong to a single species is further supported by electrophoretic evidence. A new species of Neorossia, N. leptodons, is identified and described, differing from the only described representative of this genus, N. caroli (Joubin, 1902), in the shape of the radular teeth. The two species were also shown to differ using multivariate statistical techniques. N. caroli is redescribed from the holotype and additional material. In addition, specimens of Neorossia from southeastern Australia are compared electrophoretically with R. australis. It was found that members of these two genera differed for 66% of loci.