Histochemical observations on the distribution of various oxidative and phosphorylative enzymes in larval digeneans parasitizing Bithynia tentaculata (Mollusca: Gastropoda).

Abstract

A comparative histochemical study is made on the distribution of succinate dehydrogenases, isocitrate dehydrogenases, malate dehydrogenases, glucose-6-phosphate dehydrogenases, α-glycerophosphate dehydrogenases, alcohol dehydrogenases, lactate dehydrogenases and glycogen phosphorylases in the tissues of sporocysts, rediae, cercariae and metacercariae parasitizing the gastropod mollusc Bithynia tentaculata. The results suggest that metabolic sequences resembling the conventional Embden–Meyerhoff pathway, the Pentose-Phosphate cycle and Krebs’ citric acid cycle may be operational in these larval digeneans. Heaviest enzyme activity is evident in the redial pharynx, the cercarial and metacercarial sucker and in the cercarial tail. Presumably the enzymes giving this heavy reaction form part of the energy producing mechanism for these active organs. Encysted metacercariae show a very heavy enzyme activity when compared with the sporocysts and developing cercariae of the same species. This is presumably associated with the breakdown of food storage materials, particularly glycogen, by these encysted stages.