HISTOCHEMICAL AND BACTERIOLOGICAL STUDIES ON DIGESTION IN NINE SPECIES OF LEECHES (ANNELIDA: HIRUDINEA)

¹ Department of Zoology, The University of Leeds, England

1. Histological, histochemical and bacteriological methods have been used to study digestion and the nature and source of digestive enzymes in nine species of leech.

2. The gastrodermis is not differentiated morphologically into secretory and absorptive structures and there is little difference in the structure of the crop or intestine.

3. Endopeptidases, which initiate proteolysis in most animals, lipases and amylases do not appear to be produced by the leech digestive system.

4. The possibility that the gut flora is concerned in digestion in compensation for the lack of endogenous enzymes, has been investigated using mass cultures of the microorganisms normally present in crop and intestine. In two species the combined hydrolytic capacities of the gut flora are considered sufficient for it to play an important part in digestion of proteins, fats and carbohydrates; and in the other species there is evidence that it can participate to a lesser but still significant extent.

5. Exopeptidases, as typified by the presence of aminopeptidases, are produced in the intestinal gastrodermis and can be consistently demonstrated irrespective of the nutritive state of the animal. There is evidence that they act both intra- and extracellularly.

6. It is suggested that the exopeptidases play a part different from their normal one in animal digestive physiology, in that they act in the absence of endopeptidases by slowly degrading protein chains by progressive removal of terminal units. This proteolysis supplements any effected by the gut flora.

7. Acid and alkaline phosphatases are consistently present in the gastrodermis of the leech and are believed to be concerned with absorption of material from the gut lumen.

This article has been cited by other articles:

				Y. Kikuchi and T. Fukatsu Endosymbiotic Bacteria in the Esophageal Organ of Glossiphoniid Leeches Appl. Envir. Microbiol., September 1, 2002; 68(9): 4637 - 4641. [Abstract] [Full Text] [PDF]