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  • 1
    Electronic Resource
    Electronic Resource
    Growth and population structure in the infaunal bivalve Yoldia eightsi in relation to iceberg activity at Signy Island, Antarctica (1993)
    Springer
    Marine biology 117 (1993), S. 235-241 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345668
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  • 2
    Electronic Resource
    Electronic Resource
    Pelagic larval development in the brooding Antarctic brachiopod Liothyrella uva (1994)
    Springer
    Marine biology 120 (1994), S. 279-286 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349689
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  • 3
    Electronic Resource
    Electronic Resource
    Population genetics of the Antarctic heteronemertean Parbolasia corrugatus from the South Orkney Islands (1998)
    Springer
    Marine biology 131 (1998), S. 1-13 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050290
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  • 4
    Electronic Resource
    Electronic Resource
    Variations between winter and summer in the toxicity of copper to a population of the mysid Praunus flexuosus (2000)
    Springer
    Marine biology 137 (2000), S. 631-636 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270000383
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  • 5
    Electronic Resource
    Electronic Resource
    Larval development in the Antarctic nemertean Parborlasia corrugatus (Heteronemertea: Lineidae) (1993)
    Springer
    Marine biology 116 (1993), S. 301-310 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350020
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  • 6
    Electronic Resource
    Electronic Resource
    Reproductive patterns in the Antarctic brachiopod Liothyrella uva (1998)
    Springer
    Marine biology 132 (1998), S. 153-162 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050381
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  • 7
    Electronic Resource
    Electronic Resource
    A pelagic bryozoan from Antarctica (1995)
    Springer
    Marine biology 123 (1995), S. 757-762 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349118
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  • 8
    Electronic Resource
    Electronic Resource
    Growth and tissue mass cycles in the infaunal bivalve Yoldia eightsi at Signy Island, Antarctica (2000)
    Springer
    Polar biology 23 (2000), S. 420-428 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Shell growth in Yoldia eightsi was measured over an austral summer and winter in 1992. In specimens 〈 12 mm length, growth was not significantly different between summer and winter periods, and the fastest recorded rate, 6.3 μm day−1 was for 5-mm individuals during the winter. In summer, specimens of all lengths grew significantly, but in winter bivalves 〉 27 mm length did not increase in length. Tissue dry and ash-free dry mass (AFDM) cycles were assessed at monthly intervals between December 1988 and January 1991. ANCOVA indicated significant interannual and seasonal effects on this cycle. Tissue mass increased in the summer, coinciding with the phytoplankton bloom and the period of maximum sedimentation of organic material from the water column. A standard 20-mm-length animal reached a maximum AFDM of 114 mg in February 1990. The minimum value (68 mg AFDM) throughout the 2 years of measurements was in early December 1988, at the end of the austral winter. Periods of tissue mass increase were, therefore, decoupled from shell growth, at least in juveniles. Tissue mass was significantly higher in 1990 than 1989, which was mainly due to high organic contents in the summer (January to May). This was not consistent with the pattern of organic content in the sediments at the study site, but was in phase with the cycle in sediment chlorophyll a content. Tissue mass increase depended on major resource input during the summer, but Y. eightsi was capable of maintaining winter condition from stocks of benthic microalgae in years of poor ice cover. Tissue mass declined between April and July each year. This was accompanied by large falls in tissue ash content, and coincided with the spawning period in early June. These are the first monthly tissue mass data collected over a 2-year period for an Antarctic mollusc. They are the first such data indicating seasonal variation in tissue mass and showing a decoupling of shell and tissue growth in a polar bivalve. The P/B ratio calculated from these data was 0.106, which is slightly lower than previous values found for this species, but is in line with general values for Antarctic marine benthos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050463
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  • 9
    Electronic Resource
    Electronic Resource
    Intracellular pH and energy metabolism in the highly stenothermal Antarctic bivalve Limopsis marionensis as a function of ambient temperature (1999)
    Springer
    Polar biology 22 (1999), S. 17-30 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in oxygen consumption, ammonia excretion and in the acid-base and energy status of various tissues were investigated in the cold stenothermal Antarctic bivalve, Limopsis marionensis, and compared to similar data in the limpet, Nacella concinna, for an assessment of thermal sensitivity. Oxygen consumption of L. marionensis varied between −1.5 and 2°C with a Q 10 of 2.2. Ammonia excretion could only be detected in animals exposed to elevated temperature for periods in excess of 45 days and close to death and it is interpreted as the onset of protein and amino acid catabolism with starvation under temperature stress. In L. marionensis any change in temperature as well as starvation stress at constant temperature induced a decrease in phospho-l-arginine and ATP levels. However, only temperature stress resulted in a drop in the Gibb's free energy change of ATP hydrolysis. Intracellular pH rose in all tissues during upward or downward temperature changes of only 1.5 or 2°C for 24 h with a concomitant trend to accumulate succinate and acetate in the tissues. These changes are seen to reflect disturbances of the tissue acid-base and energy status with any under- or overshoot in aerobic metabolic rate during a temperature decrease or increase. Elevated temperature at 2°C during 2 weeks of incubation resulted in continued net ATP depletion, at low levels of ATP free energy. This indicates long-term stress, which was also mirrored in the inability to establish a new steady-state mean rate of oxygen consumption. Incubation at even higher temperatures of 4 and 7°C led to an aggravation of energetic stress and transition to an intracellular acidosis, as well as a fall in oxygen consumption. In N. concinna a drop in energy levels was also visible at 2°C but was compensated for during long-term incubation. In conclusion, L. marionensis will be able to compensate for a temperature change only in a very narrow range whereas the thermal tolerance window is much wider in N. concinna. The inability of the metabolic rate to rise continually and the concomitant transition to anaerobic metabolism and long-term energetic stress characterize the upper critical temperature. Stenothermality is discussed, not only as reflecting the permanent and very stable low temperature in the natural environment, but also regarding dif- ferences in the level of activity and aerobic scope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050386
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons (1999)
    Springer
    Journal of comparative physiology 169 (1999), S. 597-604 
    Details
    ISSN: 1432-136X
    Keywords: Key words Antarctic fish ; Temperature ; Mitochondrial respiration ; Proton leakage ; Isocitrate dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The thermal sensitivity of mitochondrial function was investigated in the stenothermal Antarctic fish Lepidonotothen nudifrons. State 3 respiration increases with increasing temperature between 0 °C and 18 °C with a Q 10 of 2.43–2.63. State 4 respiration in the presence of oligomycin, an inhibitor of mitochondrial ATP synthase, quantifies the leakage of protons through the inner mitochondrial membrane, which causes oxygen consumption without concomitant ATP production. This parameter shows an unusually high Q 10 of 4.21 ± 0.42 (0–18 °C), which indicates that proton leakage does not depend merely on ion diffusion but is an enzyme-catalysed process. The differential thermal sensitivity of oxidative phosphorylation (=state 3) and proton leakage (=state 4 in the presence of oligomycin) leads to progressive uncoupling of the mitochondria and decreased efficiency of oxidative phosphorylation under in vivo conditions if the body temperature of L. nudifrons increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050260
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