Les osidases digestives de l'escargot Helix aspersa: localisations et variations en fonction de l'état nutritionnel

Abstract

Osidases were studied in brown garden snails, Helix aspersa Müller, fed or starved for 4 or 7 weeks. The digestive tract was divided into seven regions: oesophagus, crop, stomach, intestine, rectum, salivary glands, and digestive gland. The results revealed the presence of a large number of enzymes that attack alimentary carbohydrates. However, α-heterosides and starch were poorly hydrolysed, and amylase was not derived from saliva. Enzymatic secretions continued in snails subjected to 7 weeks of starvation and accumulated in the stomach, while these enzymes were active mainly in the oesophagus and the crop during nutrition. Several hypotheses are presented, including that the most active enzymes, mannanases and cellulases, may be secreted both by the salivary glands and by the digestive gland. A similar distribution is postulated for two oligosaccharidases, maltase and saccharase. Since a bacterial flora exists in the digestive tract, we also consider the possibility of a synergistic activity between osidases from the snail and those originating from the microflora.