Activities of the digestive enzymes in the gut and in tissue culture of a tropical geophagous earthworm, Polypheretima elongata (Megascolecidae)

Abstract

Endogeic geophagous earthworms from tropical areas seem to digest soil organic matter through a mutualist earthworm microflora-digestion system and the intestinal mucus produced by earthworms was supposed to play a central role in the process of digestion. A large range of glucosidic substrates characteristic of plant material was used to reveal the activities of digestive enzymes in the gut (wall and contents) of Polypheretima elongata. This worm consumes some plant substrates tested and is able mainly to degrade root and fungal substrates. It corroborates that tropical endogeic earthworms feed on litter debris and soils poor in organic matter. These glucosidic activities were higher than those found previously in Pontoscolex corethrurus. The in vitro tissue culture of gut wall allowed us to infer that P. elongata can synthesize by itself all its extra and intracellular enzymes, contrary to P. corethrurus which requires the microflora of the soil ingested in order to hydrolyse some substrates such as cellulose and mannan. It should be interesting to compare cellulases and mannanases of both earthworms after extraction and purification and to study the mechanisms by which P. corethrurus may enhance microbial activities.