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.

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.

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.

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.

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.

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.

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.