Metabolism and feeding in the Antarctic brachiopod Liothyrella uva : a low energy lifestyle species with restricted metabolic scope

The effect of feeding on metabolism (specific dynamic action; SDA) was assessed in the articulate brachiopod Liothyrella uva (Broderip, 1833) at Signy Island, Antarctica. The response was low and on a much longer timescale than previously reported SDA responses. Oxygen consumption rose post-prandially to a peak which was 1.64 $\times $ higher than the prefeeding basal metabolic rate. The response peaked on the 5$^{\text{th}}$ day and returned to basal levels on the 18$^{\text{th}}$ day after feeding. Maximum metabolic scope was therefore restricted, and was 0.41 $\mu $molO$_{2}$ h$^{-1}$ (24.5 microwatts) for a 290 mg ash-free dry mass individual. Unusually ammonia excretion was little affected by feeding, except for a short sharp peak on the 4$^{\text{th}}$ post-prandial day. Metabolic O:N ratios were very low, ranging from 2.9 to 6.6 and indicated an almost sole use of protein to fuel metabolism throughout. Urea excretion showed no pattern in relation to feeding, and accounted for around 7% of nitrogen excreted. It is suggested that metabolic scope is limited in L. uva for two reasons: because it has evolved to live at low temperatures and because of phylogenetic limitations related to articulate brachiopod lifestyles