THE INFLUENCE OF FEEDING ON OXYGEN-CONSUMPTION AND NITROGEN-EXCRETIONIN THE ANTARCTIC-NEMERTEAN PARBORLASIA-CORRUGATUS

The large nemertean Parborlasia corrugatus is common in nearshore bent hic marine habitats around Antarctica, where it is an important predat or and scavenger. Oxygen consumption and nitrogen excretion rates in w orms freshly sampled from the field were low but similar to those repo rted for other polar marine ectotherms. Nitrogen was excreted primaril y as ammonia (87%), with smaller amounts of urea (4%) and amines (9%). The O : N atomic ratio was low (10.4), indicating that free or protei n-derived amino acids were important metabolic substrates. When worms were fed at ration levels ranging from 20% to 110% of body mass, both oxygen demand and ammonia excretion increased after feeding in a class ic specific dynamic action response. Peak postprandial oxygen consumpt ion was low (range, 1.5-2.6 times the prefeeding rate), and the durati on of the specific dynamic action was unusually long (>30 d). Both the energy used and the nitrogen excreted in the specific dynamic action scaled with meal size, although the fractions of ingested carbon and n itrogen used or lost were both very low, probably because of the large ration levels. We conclude that Parborlasia corrugatus has only a lim ited ability to increase its metabolic rate following a meal and, as a result, takes many days to process that meal fully.