The ultrastructure of the epidermis and associated structures in the metacercaria cercaria and sporocyst of Diplostomum phoxini (Faust, 1918).

Abstract

Ultrastructural studies of the epidermis of the metacercaria of Diplostomum phoxini show a folded outer plasma membrane which increases the surface for the absorption of nutrients during early development. Folding is less in the adult where nutrients are absorbed by the adhesive or feeding organ and the mouth. In the sporocyst which has no mouth nutrients are absorbed through the surface which is increased by branched processes. Spines on the adult develop in the metacercaria but do not reach the surface. Spines on the cercaria which help in attachment to the fish second intermediate host are lost after entry new spines developing later. The cercaria tail bears sense receptors, probably rheoreceptors. Three types of secretion bodies regularly arranged in the outer epidermal layer of the metacercaria occur in the adult but more sparsely. The adhesive organ is not fully developed in the metacercaria but the lappets are complete and contain three types of gland cells. Alkaline phosphatase possibly concerned with extracorporeal digestion is present in the adhesive organ and possibly the epidermis of the metacercaria and acid phosphatase concerned with intra cellular digestion is present throughout the body.