Activity and origin of digestive enzymes in gut of the tropical earthworm Pontoscolex corethrurus

Abstract

Activities of glucidic digestive enzymes in the gut (content plus walls) of a tropical endogeic earthworm, Pontoscolex corethrurus, have been assayed. In order to determine the origin of the enzymes found in the gut, the wall tissues were cultured in vitro, and enzymatic activities were measured both in the cultured tissues and in the culture medium. The earthworm possesses a weak but quite complete enzyme system. In the gut, the enzymes were capable of degrading the following substrates: heteroside (N-acetylglucosamine), oligosaccharides (maltose, laminaribiose) and polysaccharides (starch, laminaran, pullulan, microcrystalline cellulose, carboxymethylcellulose, mannan, glucomannan and caroub galactomannan, lichenin). The strongest enzymatic activities were located in the foregut and midgut. Among the main enzymes found in the gut, cellulase and mannanase were neither detected, in the cultured tissues nor in the culture medium, which indicates that these two enzymes were produced by micro-organisms ingested with the soil. The oligosaccharidase and heterosidase activities were higher in the cultured tissues than in the medium, which was not the case for the polysaccharidases.