Growth and metabolism in the Antarctic brachiopodLiothyrella uva

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Abstract
Summer and winter growth rates were assessed separately for a population of the Antarctic brachiopodLiothyrella uvabetween early January 1992 and December 1993. Annual shell growth rates (1.6–2.3 mm yr−1for a 5 mm individual; 0.96–1.44 mm−1for a 20 mm specimen) were two to six times slower than those reported for temperate species. Growth in specimens less than 20 mm in length was faster in 1992 than in 1993, although differences between years over the whole size range were not significant. Surprisingly, growth was much faster in winter periods than during the summers. A 5 mm long individual grew five times faster in winter than in summer, and for a 20 mm long specimen the difference was 13 times. This runs contrary to current ideas on the effects of seasonality on the biology of polar marine invertebrates, but may be an effect of maximizing the efficiency of resource utilization. Comparisons with previous work showed shell growth to be decoupled from periods of tissue mass increase, and also from the main period of phytoplankton productivity. Oxygen consumption of 75 of the specimens used in the growth study was measured to test the hypothesis that basal metabolic rates should be inversely correlated with growth rates. Unexpectedly, an analysis of residuals produced no significant relationship, positive or negative, between growth rate and basal metabolism (F= 1.37,p=0.25,n= 75).