Presence of a partial urea cycle in the leech,Poecilobdella granulosa

Ornithine carbamoyltransferase (OCT) and arginase, but not arginine synthetase (AS), were detected in the body wall and gut tissues of the leech. The activities of these enzymes were not altered by starvation. The high activity of arginase in body wall is probably due to the association of the latter with botryoidal tissue. Hirudineans, which evolved from oligochaete ancestors, appear to have lost the citrulline-arginine segment of the urea cycle due to their ammonotelic mode of nitrogen excretion.S. N. and B. J. thank the Council of Scientific & Industrial Research and the Department of Ocean Development, Government of India, respectively for the award of research fellowships.