Article: Direct observation of contact digestion in inside-out oriented Aurelia aurita polyps.

Extracellular digestion in a scyphozoan polyp has been assumed to be mediated by digestive enzymes freely secreted into the small and simple gastric cavity ("luminal digestion") (1). But, histological examination of Aurelia aurita polyps, fixed at various time intervals after ingestion of an Artemia nauplius, indicated that the prey is in intimate contact with the polyp's gastrodermis throughout digestion, and that digestive enzyme secretion, extracellular digestion, and endocytosis are all highly confined to this region of contact ("contact digestion") (Bumann, Kuzirian, and Storch, in prep.). No digestive enzyme activity was detected elsewhere in the gastric cavity. To ...