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The seasonal energetics of the Antarctic bivalve Laternula elliptica (King and Broderip) at Rothera Point, Adelaide Island

The seasonal energetics of the Antarctic bivalve Laternula elliptica (King and Broderip) at Rothera Point, Adelaide Island,10.1007/s003000100251,Polar

The seasonal energetics of the Antarctic bivalve Laternula elliptica (King and Broderip) at Rothera Point, Adelaide Island   (Citations: 22)
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Seasonal changes in feeding activity, metabolic rate and major tissue energy concentrations of the infaunal bivalve Laternula elliptica were monitored over a 12°month period in relation to phytoplankton standing stock. Chlorophyll a concentration displayed the prolonged winter minima and intense annual summer peak characteristic of polar environments. Divers made regular observations on the feeding activity of L. elliptica throughout the year, and siphons were completely withdrawn below the sediment surface at the start of the study in early September 1998. Siphons reappeared as chlorophyll concentrations rose at the end of September and these concentrations continued until late May 1999 when siphons were again withdrawn. There were, therefore, around 4 months in the austral winter when L. elliptica did not feed. Oxygen consumption rates were highly seasonal, varying from 4.3 µmol h-1 late in the winter (August 1999) to 12.9 µmol h-1 in summer (March 1999) for a 50°mm shell height individual, indicating a summer increase in oxygen consumption over winter levels of H&#503.0. Nitrogen was excreted as 90% ammonium and 10% urea, and excretion rates were also highly seasonal. The O:N ratio did not vary significantly with size in winter (September, August), but declined with shell length in summer (November, January and March), indicating that larger bivalves used a higher proportion of protein to fuel metabolism than younger animals when feeding in summer. O:N ratios in August 1999 ranged from 3 to 16, indicating a predominantly protein-based metabolism. ANCOVA showed that regressions of dry tissue masses of major non-reproductive body components (musculature, ctenidia and digestive tissue) against shell height did not change between late winter and late summer. ANCOVA also showed that the regression slope for gonad mass against shell height was greater in late summer than late winter (slope F=7.37, P=0.009), and gonad mass was greater in all animals by late summer. Although tissue masses remained constant, energy content of non-reproductive tissues (especially musculature) declined from summer to winter. Muscle tissue also showed the greatest reduction in protein content, which was consistent with O:N estimates of primarily protein-based metabolism, especially in winter. Reduction in whole body energy content (5.84 kJ) agreed closely with total power utilisation during winter estimated from oxygen consumption (5.78 kJ). The data also showed that in contrast to temperate bivalve species, L. elliptica survives the prolonged polar winter with little reduction in body mass.
Journal: Polar Biology - POLAR BIOL , vol. 24, no. 7, pp. 523-530, 2001
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    • ...Studies initially focused on its ecology [2], and general physiology: reproduction [3,4], development [5,6], growth [7,8] and seasonal energetics [9,10]...

    Melody S Clarket al. Insights into shell deposition in the Antarctic bivalve Laternula elli...

    • ...Adapted to extreme low temperatures and seasonality of food supply in the Antarctic marine environment, L. elliptica retreats its siphons during the austral winter, and reduces its metabolic activity using its energy reserves to maintain only vital activities (Brockington 2001)...
    • ...Studies about the ratio of the oxygen consumption to ammonia excretion rates (O:N ratio) of this bivalve have shown that its energy metabolism is predominantly protein based both during summer as well as in winter (Brockington 2001)...
    • ...Use of proteins for energy requirements leads L. elliptica to excrete about 90% of its nitrogen in the form of ammonia and 10% in the form of urea (Brockington 2001)...
    • ...To this end, the adaptation of the herbivore Wlter-feeding L. elliptica to the extreme conditions of temperature and seasonal energy inputs imposed by the Antarctic marine environment was investigated in relation to its capacity to control its oxygen consumption (Peck et al. 2002) and to reduce its energy metabolism rates depending on the seasonal supply of phytoplankton in the water column (Brockington 2001)...
    • ...Studies on the energy metabolism of this bivalve have shown that proteins are the principal energy substrate, in summer (diet proteins) as in winter (endogenous proteins) (Brockington 2001; Ahn et al. 2003)...
    • ...In this case, the catabolism of protein amino acids results in the excretion of nitrogen typical of ammoniotelic animals, basically composed of 10% urea and 90% ammonia (Brockington 2001)...
    • ...On the other hand, though the aerobic energy metabolism has been the subject of some studies (Ahn and Shim 1998; Brockington 2001; Pörtner et al. 2006), the aerobic ATP-generating pathway in the main tissues of L. elliptica has not been studied in the context of its protein-based metabolism...

    Edson Rodrigueset al. Arginine metabolism of the Antarctic Bivalve Laternula elliptica (King...

    • ...Both the Southern Ocean sea urchin, Sterechinus neumayeri, and the Antarctic soft shelled clam, Laternula elliptica, have reduced metabolic rates in winter when food availability is very low but water temperature is only 3 °C below summer temperatures (Brockington 2001; Brockington and Peck 2001)...
    • ...The metabolism of L. elliptica is primarily fuelled by protein throughout the year, either by the use of protein-rich food, or through the use of body stores during starvation (Brockington 2001)...
    • ...These data were compared with information on seasonal variation in metabolic rates (Brockington 2001) to investigate the importance of the seasonal reduction of activity to the energy budget...
    • ...Calculation of seasonal oxygen consumption was restricted to a standard 50-mm shell length individual to allow comparison with values calculated by Brockington (2001)...
    • ...By estimating the costs of siphoning activity in L. elliptica, we calculated a value (3.7) that is very similar to the seasonal diVerence (3.0) between maximum and minimum metabolic rates of L. elliptica as measured by Brockington (2001)...
    • ...Much of the diVerence between the maxima from the current study and those of Brockington (2001) may be due to interannual variability in the timing and the intensity of the plankton bloom...
    • ...In 2004/2005 the maximum metabolic rate was calculated in February, whereas in 1999 the minimum was recorded a month later, in March (Brockington 2001)...
    • ...Seasonal variation in activity therefore contributes signiWcantly to the seasonal reduction in metabolic rates measured by Brockington (2001)...

    Simon A. Morleyet al. Hypoxia tolerance associated with activity reduction is a key adaptati...

    • ...The photometric assay used an ammonium cell test based on the phenol hypochlorite method (Brockington 2001)...

    E. Brodteet al. Temperature-dependent energy allocation to growth in Antarctic and bor...

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