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  • Springer  (47,220)
  • International Union of Crystallography  (7,535)
  • Public Library of Science
  • 2020-2022
  • 2015-2019
  • 2005-2009  (56,801)
  • 1950-1954
  • 1945-1949
  • 2007  (56,801)
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  • 2020-2022
  • 2015-2019
  • 2005-2009  (56,801)
  • 1950-1954
  • 1945-1949
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  • 11
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    Springer
    In:  Marine Biology, 152 (4). pp. 981-990.
    Publication Date: 2021-09-06
    Description: Deep-sea squids, Moroteuthis ingens and Gonatus antarcticus, were collected in the slope waters off the Falkland Islands and their reproductive systems preserved and investigated onshore. Changes in oocyte length-frequencies at maturation and spawning, and their fecundity were studied. These squids, as well as many other species, are characterised by a synchronous oocyte growth and ovulation. Oviducts are not used for ripe egg accumulation and consequently the universal scale of Lipinski (1979) cannot be applied to assign female maturity. M. ingens spawns near the bottom; its fecundity is 168–297 thousand eggs. Maximum egg size is 1.8–2.7 mm. G. antarcticus spawns midwater; its fecundity is 10–25 thousand eggs. Egg size is 3.2–3.3 mm. In M. ingens spawning takes place in the austral autumn and winter, in G. antarcticus—in austral winter. Our data and the literature data show that the so-called “synchronous ovulation” probably occurs in all deepwater squids. This pattern is very rare among fish, but is quite common among benthic octopods that brood their egg masses.
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  • 12
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    Springer
    In:  Reviews in Fish Biology and Fisheries, 17 (2-3). pp. 183-195.
    Publication Date: 2021-09-03
    Description: The aim of this study was to determine how size, age, somatic and reproductive condition, abundance and egg production of southern calamary spawning aggregations changed during the spawning season in each of 2 years. During the spawning period in at least one of the years there was a decline as much as 20% in average size, 50% in somatic condition, 28–34% in size-at-age, 26–29% in reproductive status, as well as abundance and reproductive output of the stock declining during the spawning season. However, this change was not a function of the population becoming reproductively exhausted, as the aggregation was composed of different individuals with different biological characteristics. In each month the average age of individuals was ca. 6 mo, indicating that squid that had hatched at different times had entered the spawning aggregations, suggesting that the aggregation was made-up of a succession of microcohorts. Currently, management of many squid populations assumes that there is a single cohort in the aggregation. Therefore, estimating stock biomass at the start of the spawning season cannot be used as the population is constantly changing as micro-cohorts move into the aggregation. An instantaneous estimate of the spawning biomass, independent of fishing activity may be obtained by quantifying the density of deposited eggs. The strategy of individuals with a diversity of life history characteristics coming together in a single spawning aggregation may ensure the phenotypic and genetic diversity required to guarantee successful recruitment of this short-lived species. Therefore, temporally structured protection from harvest throughout the spawning season will ensure maintenance of this population diversity.
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  • 13
    Publication Date: 2021-08-31
    Description: Pholidoteuthis is unusual amongst genera of squid in that the mantle is beset with close-packed dermal cushions (scales). Despite frequent reference to species in this genus, considerable systematic confusion surrounds usage of the generic name, erected prematurely given that the same systematic characters apply for the earlier Tetronychoteuthis Pfeffer, 1900, and species attributed to it. The synonymy and ontogenetic morphology of Pholidoteuthis massyae (Pfeffer 1912) new comb., the senior synonym of P. boschmai Adam, 1950, is reported. The relationship between this species and others referred to Tetronychoteuthis, Lepidoteuthis, the Pholidoteuthidae Adam, 1950, Lepidoteuthidae Pfeffer, 1912 and Octopoteuthidae Berry, 1912, is discussed. A conjectural account of the mechanics of mating in P. massyae is provided based on the nature of spermatophore insertion in the female mantle, and modification to the terminal region of the male’s genital apparatus.
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  • 14
    Publication Date: 2021-08-27
    Description: We have applied the novel analytical method NanoSIMS to cephalopod statoliths for the first time in order to analyse their chemical microstructure, using a spatial resolution of 400 nm. This technique makes it possible to analyse in situ nano-scale chemical variations between increment layers. In statoliths of the boreoatlantic armhook squid Gonatus fabricii, we found distinct concentration patterns indicating a periodicity in strontium and sodium distributions. Sr and Na show a negative relation, both elements showing alternating patterns where the increments vary in width between approximately 1 and 5 μm. Results suggest, that aragonite deposited during the night is rich in Na and poor in Sr, while aragonite deposited during the day is rich in Sr and poor in Na. This study demonstrates the excellent suitability of NanoSIMS for nano-scale microchemical analyses of aragonite, providing new information on calcification processes and individual life histories. Possible future fields of application include not only cephalopod statoliths, but also virtually all biomineralized tissues in aquatic organisms like fish otoliths, gastropod statoliths, bivalve shells, foraminifers and corals.
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  • 15
    Publication Date: 2021-08-27
    Description: The use of statolith chemistry to trace migration pathways and distinguish populations of cephalopods is based on the assumption that the elemental composition of statoliths is influenced by physicochemical properties of the ambient environment. However, such influences have not been investigated experimentally up until now. This study presents the first microchemical analyses of cephalopod statoliths obtained from laboratory experiments under different controlled temperature and salinity conditions. Our results show that statolith chemical composition is strongly related to both salinity and temperature in ambient waters. The Ba/Ca ratio is negatively related to temperature and shows no relation to salinity. The I/Ca ratio is positively related to temperature and negatively to salinity. No Sr/Ca relation was found to either salinity or temperature, suggesting that the well-established proxy strontium is not as useful in cephalopod statoliths as in other biomineralized aragonites. Microanalysis of trace elements, however, shows an enormous potential for field studies on distribution, migration and stock separation of cephalopods. Furthermore, Synchrotron X-ray Fluorescence Analysis is introduced as a promising novel method for statolith analysis, providing a spatial resolution of typically 10–15 μm combined with detection limits down to 0.5 ppm.
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  • 16
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    Springer
    In:  Reviews in Fish Biology and Fisheries, 17 (2-3). pp. 353-365.
    Publication Date: 2021-08-27
    Description: We describe here two new species of oegopsid squids. The first is an Asperoteuthis (Chiroteuthidae), and it is based on 18 specimens. This new species has sucker dentition and a funnel–mantle locking apparatus that are unique within the genus. The second new species is a Promachoteuthis (Promachoteuthidae), and is based on a unique specimen. This new species has tentacle ornamentation which is unique within the genus. We also describe a new genus and a new species of sepioid squid in the subfamily Heteroteuthinae (Sepiolidae) and it is based on four specimens. This new genus and species exhibits unique modifications of the arms in males.
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  • 17
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    Springer
    In:  Reviews in Fish Biology and Fisheries, 17 (2-3). pp. 337-344.
    Publication Date: 2021-08-23
    Description: The concept of a Barcode of Life Database (BoLD) for the Class Cephalopoda (Phylum Mollusca) was introduced at the Cephalopod International Advisory Council (CIAC) symposium in Hobart, Australia, February 2006. This suggestion was met with significant interest, concern and debate. This review attempts to describe the concept of the BoLD initiative and to outline considerations and concerns specific to a cephalopod BoLD.
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  • 18
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    Springer
    In:  Reviews in Fish Biology and Fisheries, 17 (2-3). Art.-Nr.: 101.
    Publication Date: 2021-08-18
    Description: Statolith size and growth was used to determine the influence of abiotic factors on the growth of Loligo vulgaris and Sepioteuthis australis embryos. Recently spawned egg masses collected from the field were incubated in the laboratory under different levels of light intensity, photoperiod, or short periods of low salinity (30‰). Double tetracycline staining was used to follow statolith growth. In L. vulgaris constant light conditions produced significantly slower growth in the embryonic statoliths and embryos held at summer photoperiod had slower statolith growth than those held at winter photoperiods. However once they hatched out there was no evidence that photoperiod affected statolith growth. After hatching, in all photoperiods statolith growth rates decreased in comparison with late embryonic rates. In S. australis embryos, differences between the high and medium light intensities for summer and intermediate photoperiods were found, suggesting that under summer incubation temperature, longer daylengths at medium light intensity favoured higher statolith growth for this species. In comparison to controls, slower statolith growth in S. australis embryos due to low salinity only occurred when exposed for 72 h. Comparison with previous studies indicates that temperature seems to be the main abiotic factor influencing statolith growth during early stages, however, interactions among all abiotic factors needs to be determined as well as the unknown influence of other isolated factors, e.g., oxygen concentration within the egg mass.
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  • 19
    Publication Date: 2021-08-09
    Description: A two day workshop on Southern Ocean cephalopods was held in Hobart, Tasmania, Australia prior to the triennial 2006 Cephalopod International Advisory Council (CIAC) symposium. The workshop provided a second international forum to present the current state of research and new directions since the last Southern Ocean cephalopod meeting held in 1993. A major focus of the workshop was trophic ecology and the use of a variety of tools that can be applied in Southern Ocean trophic studies for both cephalopod and predator researchers. New tools that are being used as trophic indicators and tracers in food chain pathways include stable isotope, heavy metal and fatty acid signature analysis. Progress is also being made on understanding squid population dynamics in relation to other key components of the ecosystem by incorporating squid data in ecosystem models. Genetic barcoding is now of great value to fish taxonomy as well as other groups and it is expected that a cephalopod barcoding initiative will be an important tool for cephalopod taxonomy. There is a current initiative to produce a new cephalopod beak identification guide to assist predator biologists in identifying cephalopod prey items. There were also general discussions on specific taxonomic issues, Southern Ocean Cephalopod paralarvae and parasites, and suggestions for future CIAC workshop topics.
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  • 20
    Publication Date: 2021-08-05
    Description: We describe the feeding habits of 70 blue sharks (Prionace glauca) and 39 salmon sharks (Lamna ditropis) caught at 0–7 m depth at night by research drift gillnets in the transition region of the western North Pacific during April–May of 1999 and 2000. Blue sharks of 50–175 cm total length fed on a large variety of prey species, consisting of 24 species of cephalopods and 16 species of fishes. Salmon sharks of 69–157 cm total length fed on a few prey species, consisting of 10 species of cephalopods and one species of fish. Important prey for the blue sharks were large, non-active, gelatinous, meso- to bathypelagic cephalopods (e.g., Chiroteuthis calyx, Haliphron atlanticus, Histioteuthis dofleini and Belonella borealis) and small myctophid fishes. Important prey for the salmon sharks were mid-sized, active, muscular, epi- to mesopelagic squids (e.g. Gonatopsis borealis, Onychoteuthis borealijaponica and Berryteuthis anonychus). Our results suggest that blue sharks feed on cephalopods mainly during the daytime when they descend to deep water. Salmon sharks may feed opportunistically with no apparent diurnal feeding period. Blue sharks and salmon sharks have sympatric distribution in the transition region in spring; they have different feeding habits and strategies that reduce competition for food resources.
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