The influence of feeding on oxygen consumption and nitrogen excretion in the Antarctic nemertean Parborlasia corrugatus.

Abstract

The large nemertean Parborlasia corrugatus is common in nearshore benthic marine habitats around Antarctica, where it is an important predator and scavenger. Oxygen consumption and nitrogen excretion rates in worms freshly sampled from the field were low but similar to those reported for other polar marine ectotherms. Nitrogen was excreted primarily 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 protein-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 classic specific dynamic action response. Peak postprandial oxygen consumption was low (range, 1.5-2.6 times the prefeeding rate), and the duration 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 nitrogen used or lost were both very low, probably because of the large ration levels. We conclude that Parborlasia corrugatus has only a limited ability to increase its metabolic rate following a meal and, as a result, takes many days to process that meal fully.