J. Moll. Stud. (1994), 60,141-147 © The Malacological Society of London 1994 NITROGEN EXCRETION IN THE ANTARCTIC LIMPET NACELLA CONCINNA (STREBEL, 1908)

Excretion of ammonia, urea and primary amines (assayed as fluorescamine-positive substances, FPS) was measured in the Antarctic limpet Nacella concinna. The mean contributions to overall excretion rate were 89 % ammonia, 8 % urea and 3 % FPS, although in some individuals urea formed almost 40 % total excre-ted nitrogen and in others primary amines formed over 30%. Ammonia and urea excretion rates were not correlated, suggesting the ureagenesis has a speci-fic physiological role and is not simply an alternative end-point to ammonia. In starved limpets urea excre-tion at first increased by at least x2, and then declined to low levels after 44 days. Ammonia excre-tion also increased, but only after 20 days, and then stayed high until at least day 44. These different pat-terns confirm the independent roles of ammonia and urea production in Nacella