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Cystic spermatogenesis in the subadult, maturing and adult Greenland shark (Somniosus microcephalus) displays multiple novel features, characterized early on by an unorganized internal cellular environment of the spermatocysts (anatomically discrete follicle-like units containing a single germ cell stage and its complement of co-developing Sertoli cells). These typically show polar asymmetries due to asymmetrically distributed germ and Sertoli cells. These arise from several novel cellular rearrangements at the immature pole, including fusion of a cluster of somatic cells with newly formed cysts containing only one to three spermatogonia and that already display an excess of Sertoli cells. The subadult's germinative zone revealed an additional novelty, namely numerous previously formed somatic cell-lined rings into which spermatogonia were incorporated. A striking finding was the conspicuous rarity of the routinely discernible Sertoli mitotic figures in the hallmark cyst stage of diametric elasmobranch spermatogenesis that is known for the peak display of the latter. Scrutiny of sequentially unfolding phenomena in the linearly arranged spermatogonial generations revealed that the cellular developments at the most common type of cyst–duct transition area (comprising slender to spindle-like basophilic cells with pointed ends) were concurrent with the discreet appearance of a second dark Sertoli nucleus, a development that persisted in spermiated cysts. Spermatogenically active mature males displayed vigorous meiotic divisions. However, a scattering of their spermatid cysts also displayed shark-atypical asynchronous passage through spermiogenesis, phenomena which were exacerbated as arrested spermiogenesis in an archival collection of tissues from 13 maturing specimens. Subadult specimens revealed meiotic arrest, and foci of infiltration of leukocytes that originate from a mass of eosinophilic, granule-laden immune cells dorsally under the testis capsule. This tissue was identical to the testis-affixed bone marrow equivalent in other shark species. This tissue is likely developmentally regulated in the Greenland shark as it is absent in adults. [ABSTRACT FROM AUTHOR]

Background: The walleye pollock (Theragra chalcogramma) and Norwegian pollock (T. finnmarchica) are confined to the North Pacific and North Atlantic Oceans, respectively, and considered as distinct species within the family Gadidae. We have determined the complete mtDNA nucleotide sequence of two specimens of Norwegian pollock and compared the sequences to that of 10 specimens of walleye pollock representing stocks from the Sea of Japan and the Bering Sea, 2 specimens of Atlantic cod (Gadus morhua), and 2 specimens of haddock (Melanogrammus aeglefinus). Results: A total number of 204 variable positions were identified among the 12 pollock specimens, but no specific substitution pattern could be identified between the walleye and Norwegian pollocks. Phylogenetic analysis using 16.500 homologous mtDNA nucleotide positions clearly identify the Norwegian pollock within the walleye pollock species cluster. Furthermore, the Norwegian pollock sequences were most similar to mitochondrial genotypes present in walleye pollock specimens from the Sea of Japan, an observation supported both by neighbor-joining, maximum parsimony, and maximum likelihood analyses. Conclusion: We infer that walleye pollock and Norwegian pollock represent one single species and that Norwegian pollock has been recently introduced from the Pacific to the Atlantic Oceans. [ABSTRACT FROM AUTHOR]

Deep-sea marine fishes support important fisheries but estimates of their distributions are often incomplete as the data behind them may reflect fishing practices, access rights, or political boundaries, rather than actual geographic distributions. We use a simple suitable habitat model based on bottom depth, temperature, and salinity to estimate the potential distribution of Greenland halibut (Reinhardtius hippoglossoides). A large presence-only dataset is examined using multivariate kernel densities to define environmental envelopes, which we link to spatial distribution using a pan-Arctic oceanographic model. Occurrences generally fit the model well, although there were gaps in the predicted circum-Arctic distribution likely due to limited survey activity in many of the ice-covered seas around the Arctic Ocean. Bottom temperature and depth were major factors defining model fit to observations, but other factors, such as ecosystem interactions and larval drift could also influence distribution. Model predictions can be tested by increasing sampling effort in poorly explored regions and by studying the connectivity of putative populations. While abundances of Greenland halibut in the High Arctic are currently low, some areas are predicted to be suitable habitat for this species, suggesting that on-going sea-ice melt may lead to fisheries expansion into new areas. [ABSTRACT FROM AUTHOR]

In all 155 specimens of the high Arctic codfish Arctogadus glacialis examined for metazoan parasites, 55 specimens were from southern and northern Baffin Bay, western Greenland, and 100 specimens from north-eastern Greenland and Scoresby Sound. A total of 20 parasite taxa were recorded. A new myxozoan Gadimyxa arctica was found in southern Baffin Bay and Scoresby Sound. The gadid myxozoan Zschokkella hildae, the digeneans Gonocerca phycidis and Lecithaster gibbosus, the gill copepod Haemobaphes cyclopterina and third-stage larvae of the nematodes Anisakis simplex and Hysterothylacium aduncum were found in Scoresby Sound only. The digenean Hemiurus levinseni and third-stage larvae of the nematode Contracaecum sp. were found at all four stations. The nematodes Ascarophis spp. were found at three stations. The parasite fauna of A. glacialis from Scoresby Sound was very similar to that of 50 specimens of the closely related Boreogadus saida from the same area. [ABSTRACT FROM AUTHOR]

Abstract: This paper explores the potential of stable isotope analysis to identify the approximate region of catch of cod by analysing bones from medieval settlements in northern and western Europe. It measures the δ 13C and δ 15N values of cod bone collagen from medieval control samples collected from sites around Arctic Norway, the North Sea, the Kattegat and the Baltic Sea. These data were considered likely to differ by region due to, for example, variation in the length of the food chain, water temperature and salinity. We find that geographical structuring is indeed evident, making it possible to identify bones from cod caught in distant waters. These results provide a new methodology for studying the growth of long-range trade in dried cod and the related expansion of fishing effort—important aspects of the development of commercialisation in medieval Europe. As a first test of the method, we analyse three collections of cod bones tentatively interpreted as imported dried fish based on a priori zooarchaeological criteria. The results tentatively suggest that cod were being transported or traded over very long distances since the end of the first millennium AD. [Copyright &y& Elsevier]