GUT HISTOCHEMISTRY IN OIKOPLEURA DIOICA

Functions of the various gut regions of Oikopleura dioica were investigated by means of histochemical, histoenzymatic and immunohistochemical techniques with optical and electron microscopes. Data reveal a specific localization of the enzymatic activities and storage material along the gut. Absorptive processes (alkaline phosphatase), active transport (ATPase) and nitrogen excretion (D-amino acid oxidase) occur along the entire gut at the level of both ciliated microvllar and globular cells. The latter, typical of the left gastric lobe and the rectum, are also involved in endocytosis processes (exogenous peroxidase as a tracer) and intracellular digestion (alpha-amylase, aminopeptidase, acid phosphatase, 5'-nucleotidase, non-specific esterase). The giant cells of the gastric band participate in extracellular digestion; they contain secretory granules positive to varios hydorlytic enzymes, the activity of which is recognisable also in the faecal pellet inside the intestinal lumen. Lipid storage occurs mainly in the right gastric lobe and the vertical intestine, whereas protein storage takes place in the rectal granular cells.