The ultrastructure of the digestive cells of Argulus japonicus, Thiele 1900 (Crustacea: Branchiura)

The ultrastructure of the cells of the digestive system of Argulus japonicus is described with the use of transmission electron microscopy. Specimens of Argulus japonicus were collected from the Vaal Dam in South Africa and fixed in Todd's fixative. The samples were post fixed in osmium tetroxide and embedded in resin. The anterior midgut is composed mostly of R cells while the enteral diverticula are composed mainly of R cells in the proximal diverticules and of F cells in the distal diverticula. The posterior midgut is composed of very large papilliform B cells and of R cells. The R cells in the anterior midgut probably absorb nutrients including lipids. The F cells are filled mostly with rough endoplasmic reticulum, suggesting enzyme synthesis, while the B cells portrayed endocytotic vesicles, indicating intracellular digestion of predigested food. The R cells of the posterior midgut are less active than cells present in the anterior midgut. E cells and peritrophic membrane were not observed.