The ultrastructure of the posterior gut and caecum inAlona affinis (Crustacea, Cladocera)

Abstract

The posterior midgut, the anterior hindgut and the caecum ofAlona affinis were studied by transmission electron microscopy. The caecum arises from the junction of the entodermal midgut and the ectodermal hindgut. It consists of gastrodermis and epidermis. Because of the ultrastructural similarity of the caecum with the posterior midgut and the anterior hindgut it is concluded that the caecum is a functional supplement of the latter gut parts. But the functional significance of these gut parts is poorly understood. Some ultrastructural features suggest that they contribute in excretion and salt regulation.