Seasonal differences in citrate synthase and digestive enzyme activity in larval and postlarval antarctic krill, Euphausia superba |
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| Authors: | B Meyer R Saborowski A Atkinson F Buchholz U Bathmann |
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| Institution: | (1) Department of Pelagic Ecosystems, Alfred Wegener Institute for Polar and Marine Research, Handelshafen 12, 27570 Bremerhaven, Germany;(2) Biologische Anstalt Helgoland at the Alfred Wegener Institute, Marine Station, 27498 Helgoland, Germany;(3) Natural Environment Research Council, British Antaretic Survey, High Cross, Madingley Road, CB3 0ET Cambridge, UK |
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| Abstract: | Antarctic krill maintain large population sizes despite dramatic seasonal fluctuations in food availability, but the mechanisms
for this are still debated. The aim of this study was to compare seasonal differences in enzyme activity and respiration rates
of larval and postlarval krill to provide insights into their overwintering strategies. Respiration rates, activity of the
metabolic enzyme citrate synthase (CS), and those of the digestive enzymes laminarinase and total proteinase were measured
in austral summer west of the Antarctic Peninsula, and in autumn in the southwestern Lazarev Sea. The 100-fold difference
in chlorophyll a concentrations between the two studies is representative of the classic transition from a summer bloom to sparse winter conditions.
Correspondingly, adult krill showed reduced respiration rates and CS activity in autumn. However, their digestive enzyme activity
was significantly higher, suggesting more efficient assimilation of food at low food levels. Similar-sized larvae showed no
summer-autumn differences in respiration rates and enzyme activity, supporting suggestions that they need to feed and grow
year-round. However, trends in enzymatic activity varied between the larval stages measured, implying ontogenetic changes
in body structure and function.
Published online: 1 August 2002 |
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