ABSTRACT

This chapter considers the sites, conditions, and digestive enzymes in echinoderms. Bernard defined digestion as the cleavage of complex macromolecules or otherwise complex nutrients to simple metabolizable forms as a result of the activity of specific hydrolytic enzymes. The simplest digestive process in animals is considered to be intracellular with evolutionary trends towards greater development and specialization of the alimentary tract towards extracellular digestion. The possible involvement of bacteria in digestion was raised when Lasker and Giese showed that the large number of bacteria present in the gut of Strongylocentrotus purpuratus digested agar and a red alga, Iridaea flaccidum. The information on digestion in larvae of echinoderms is obviously very fragmentary and considerable opportunity for contributions exists. The understanding of digestion in echinoderms remains as unsatisfactory as when reviewed by Arvy, Anderson, Binyon, Ferguson. The production of acid mucus and possibly hydrolytic enzymes was postulated to result from the stimulus of cilia of the animal plate by food particles.