Proterometra macrostoma (Trematoda: Azygiidae): Functional morphology of the tegument of the redia

Abstract

Scanning and transmission electron microscopy were used to study the tegument of the redia of Proterometra macrostoma. The predominant feature of the tegument is the presence of orderly arranged channels giving the tegument a honeycomb appearance in thin sections. The channels are closely apposed like stacked cylinders and lie perpendicular to the basal lamina. The channels are about 0.75 μm long by 0.2 μm in diameter each opening to the outside by a small pore. Mitochondria are located between the basal lamina and the bases of the channels. The free surface of the tegument is amplified secondarily by annular folds and small unbranched mierovilli. In vitro experiments were then designed to test the biophysical properties of this unusual tegument with respect to the flow of water and solutes through the channels. Addition of 5 m m glucose stimulated the uptake of 14C-mannitol suggesting that a concentration gradient of 14C-mannitol was generated in the channels.