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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 31 (1959), S. 2024-2026 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth rates in the infaunal nuculanid bivalve mollusc Yoldia eightsi (Couthouy) were assessed for field populations in Factory Cove, Signy Island, Antarctica, between. February and April 1992. Daily increments in length (maximum shell dimension) ranged from 2.3 μm d-1 for a 30 mm individual to 5.1 μm d-1 for a 10 mm specimen. These growth rates were converted to annual increments, based on a growing season for the Signy population of around 5 mo, and ages for the largest individuals in the population (35 mm in length), were calculated to be ≃65 yr. Specimens of 43 mm in length have been found near this site and, if their growth rates are similar to this population, their ages would be in the order of 120 yr. Size distributions from two sites in the same Y. eightsi bed 300 m apart showed significant differences. At the more exposed site the distribution was dominated by small juveniles, with 86% of the population 10 mm in length, while 13% were 〉20 mm in length. At the less exposed site the values were 27% 〈10 mm and 56% 〉20 mm. Icebergs have often been seen grounded on the Y. eightsi bed in this study, especially on the exposed outer portion. This factor, in association with inhibition of larval settlement by high densities of large individuals, is proposed as an explanation of the observed population distributions and the absence of very large specimens in the Factory Cove population.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 120 (1994), S. 279-286 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Larvae of the Antarctic brachiopod Liothyrella uva (Broderip, 1833) were released by brooding females between 10 and 15 January 1992. They were collected and cultured for the ensuing 45 d. At release they were at the gastrula stage, and were recognisable as the usual brachiopod three-lobed larva from around 18 d after release. At ≃22 d post-release, larvae began to congregate under shell fragments placed in culture vessels as potential settlement substrata. However, the larvae showed no signs of settlement which, combined with the absence of many of the attributes of mature larvae seen in previous studies, was taken as evidence that these larvae had not reached fully competent stages. Previous work had shown that L. uva spawns in October, indicating that the developmental period lasts for a minimum of between 115 and 160 d. The release and subsequent development of larvae also shows that what was previously thought to be a brooding species combines a long brooding period with a free-swimming phase. If this is true of other brachiopod species, then there may need to be a recategorization of some species from brooding to combined brooding and free-swimming developmental types. Even though the development period in L. uva was likely to have been underestimated because a fully competent stage was not reached, a comparison with development rates for temperate species indicated a slowing of between 8 and 70 times. This dramatic slowing of development rate in brachiopods now joins similar data previously reported for echinoderms and nemerteans, suggesting that this is a very widespred, perhaps universal, attribute of Antarctic marine invertebrates.
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  • 4
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An allozyme survey, using starch-gel electrophoresis, was carried out on eight populations of the Antarctic nemertean worm Parborlasia corrugatus (McIntosh, 1876) collected from locations around the South Orkney Islands, Antarctica. These populations were separated by distances in the order of tens of kilometres. Genetic variation was estimated over 22 enzyme loci for all populations examined, giving an observed heterozygosity of 0.142. This was much lower than the expected heterozygosity (H e  = 0.201), and it was found that there was a significant deficiency of het‐erozygotes across four enzyme loci ( p ≤ 0.01). A more detailed examination of this deficiency of heterozygotes was undertaken for the six populations and six variable enzyme loci for which the most complete data sets existed. A significant deficiency of heterozygotes was found at the enzyme locus Odh-1 for four of the six populations examined ( p ≤ 0.01). Mean F is (0.240) indicated a significant ( p ≤ 0.01) within-population component of the heterozygote deficiency estimated for the six populations sampled, and this was mainly due to the␣Ap-1, Odh-1 and Pgm-1 loci. The mean F st value (0.036) was also significant ( p ≤ 0.01), indicating a degree of genetic differentiation between populations. The observed levels of genetic differentiation between populations of P. corrugatus and the significant heterozygote deficiencies were unexpected, because this species has been reported to have a long-lived planktotrophic larva. It is hypothesised that recruitment of P. corrugatus in the South Orkney Islands originates from genetically distinct populations located in the Weddell Sea and to the west of the Antarctic Peninsula. Shifts in the relative position of the Weddell Sea Front, Weddell–Scotia Confluence and Scotia Front, relative to the South Orkney Islands, provide a mechanism for variation in the origin of recruits over time.
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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Copper toxicity was tested on a coastal population of the mysid Praunus flexuosus (Müller) from Southampton Water (Southern England) under winter and summer conditions. Ten-day toxicity tests were performed on the different life-cycle stages (female, male and juvenile) present in winter (December/February) and summer (August). The individuals were in winter or summer physiological condition and were exposed to seawater to which 0, 5, 25, 75 and 200 μg l−1 copper was added. There were significantly different copper toxicity effects in winter and summer. In winter mortality was ≤ 1% at all levels of copper exposure, while in summer identical exposure levels caused mortality of up to 93%. The 96 h LC50 was 30.8 μg l−1 copper added in the summer. In winter, the low mortality prevented calculation of LC50. There were differences in responses to copper between the life-cycle stages. Juveniles were more sensitive than adults, and were severely affected within 24 h. Females were more affected than males at lower doses and shorter exposure times.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 116 (1993), S. 301-310 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryonic and larval development were followed from fertilisation to settlement in the Antarctic heteronemertean Parborlasia corrugatus (McIntosh, 1876). The first cleavage occurred 10 to 15 h after fertilisation, and the second at ≃17 h. Larvae hatched at the gastrula stage, between 170 and 200 h post-fertilisation, and were ≃150 μm in diameter. Early larval stages aggregated in dense groups near the surface of incubation vessels and were positively phototactic. Early pilidium larvae were recognisable 435 h post-fertilisation. They were 155×152 μm in size, and possessed a complete apical tuft of cilia and a full marginal band of locomotory cilia. At this stage, the gust was visible through the body wall, and the mouth was open and was ≃40 μm in diameter. Late pilidia, 222×193 μm in size, were helmet-shaped. They had an apical tuft over 100 μm long, and possessed a lobed marginal band of locomotory cilia. Pilidia were observed aggregating close to the bottom of incubation vessels 1200 to 1350 h (50 to 56 d) after fertilisation, and this was interpreted as settlement behaviour. At this stage, the apical tuft had been lost and they were highly contractile, being capable of compressing their bodies. However, neither developing juveniles within the larval envelope nor hatched juveniles were observed. Pilidia consumed the microalgae Tetraselmis suecica, Thalassiosira pseudonana and Isochrysis galbana. They also fed on particulate organic material 〈 1 μm in size, as shown by the presence of material in the guts of larvae offered filtered extracts of algal cultures. There was some indication that larvae could use dissolved organic material, since pilidia held in seawater with organic material removed did not survive as long as those in filtered seawater or in filtered water with added amino acids. However, the only larvae to exhibit settlement behaviour in the feeding experiments were those offered Tetraselmis succica and Thalassiosira pseudonana, and these required a longer development time to reach this stage than pilidia in the standard cultures, where a mixed algal diet was offered.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 132 (1998), S. 153-162 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The reproductive cycle of the Antarctic articulate brachiopod Liothyrella uva (Broderip, 1833) is described from monthly samples collected between September 1985 and July 1987 from a population at Signy Island, Antarctica. Spermatogenesis and oogenesis are described for the first time in this species. Surface dried-tissue masses for a standard individual (41 mm shell length) were calculated for the digestive diverticula, gut, lophophore and gonad from monthly dissections of 15 brachiopods. Seasonal patterns, with summer peaks, were observed in the digestive diverticula and gut. The lophophore and gonad masses did not exhibit seasonal trends. Females showed a sharp decrease in proportion of large oocytes between October and November in 1986, suggesting spawning during this period. There was no similar decrease during the same period in 1985. Mean percent spermatozoa measurements revealed a large increase in November 1985 and a rapid decline in December 1985. This suggested a large spawning event for males in 1985 which was not repeated the following year. These data indicate large inter-annual differences in reproductive activity as well as differences between males and females. They also suggest the possibility of sperm storage by females. Brood characteristics were also highly variable. The smallest brooding female was 31.5 mm in length. Some females brooded more than one developmental stage simultaneously, and variation in brood size (numbers of embryos or larvae held in the lophophore) and brood composition between individuals was high. All samples collected throughout the 2 yr period contained some females with broods. The data suggest that the reproductive strategy of L. uva is highly plastic, and that there may be three reproductive periodicities on seasonal, annual and inter-annual time scales.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 123 (1995), S. 757-762 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spherical or sub-spherical bryozoan colonies were collected from the surface waters of a coastal polynya in the southeastern Weddell Sea near Halley Station in February 1992. These are the first truly pelagic marine bryozoan colones yet recorded. The collection site is the edge of the Brunt ice shelf, which is between 150 and 250 m thick in this area, and the depth of water to the seabed is ∼-400 m. The colonies were hollow, composed of a single layer of autozooids, and appeared complete and undamaged. They were between 5.0 and 23.0 mm in diameter, were brownish in colour in life, and pale yellowish brown after preservation. Light and scanning electron microscope investigations of the colonies indicated that they belonged to the genus Alcyonidium, and they are here compared with A. flabelliforme Kirkpatrick, a known antarctic benthic species. Both a pelagic existence and hollow spherical colony form are new attributes for the phylum Bryozoa. However, because of the plasticity of form of species belonging to the genus Alcyonidium, these is not enough evidence for the introduction of a new species at this time. The colonies found may represent a previously undescribed juvenile stage of a known Alcyonidium species. It is postulated that these colonies may obtain nutrition from the often abundant populations of ice algae present in the lower layers of permanent sea-ice.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The absolute gut evacuation rate (GER) (g day−1) of Harpagifer antarcticus increased with increasing ration mass, fish mass only influenced the absolute GER at a daily ration level of 0·3% wet fish mass (approximately a maintenance ration). The relative GER (% of meal fed day−1) was also affected differently by fish and ration mass depending on the relative ration level being fed; at rations of 0·7% wet fish mass or above the relative GER decreased with increasing fish or ration mass (in such a way that the absolute GER remained constant and unaffected by fish mass). At maintenance (0·3% wet fish mass) rations the relative GER was not affected by fish size or ration mass. Thus, there appears to be a ration threshold above which the digestion physiology alters. Mass-specific GER (% g fish−1 day−1) decreased with increasing fish mass. Within a set relative ration level (% wet fish mass) an increase in fish mass decreased the mass-specific GER. At a fixed ration mass, an increase in fish mass (i.e. a reduction in the ration expressed as % fish mass) resulted in a decrease in mass-specific GER. Gut evaluation time (GET) decreased and absorption efficiency (A) increased with increasing absolute GER. The effect of ration and fish mass on the absolute and relative GER followed the same pattern irrespective of the diet, however the A and GER (% day−1 and g day−1) were higher and the GET shorter when the fish were fed shelled krill rather than amphipods.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 60 (2002), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Oxygen consumption and ammonia excretion of the Antarctic fish Notothenia coriiceps (18.4 cm LF) increased respectively two and fourfold above fasting levels 24 h after feeding with a single meal of shrimps (5.5 to 7.5% of body mass), and remained elevated for 120 h. In fasted fish, c-met positive cells in the fast muscle represented 5.5% of the total number of myonuclei. The number of c-met positive cells staining for the proliferating cell nuclear antigen was increased by 60% both 24 and 96 h after the meal, while the number of cells expressing the myogenic transcription factor, MyoD, was increased by 20% after 24 h, and by 44% after 96 h. The total numbers of c-met positive cells and cells expressing myogenic were not significantly altered 96 h following feeding. The results are consistent with an activation of myogenic progenitor cells proliferation by feeding but suggest a relatively long cell cycle time.
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