The ultrastructure of the tegument and clamp attachment organ of Gotocotyla bivaginalis (Monogenea, polyopisthocotylea)

Abstract

The tegument of Gotocotyla bivaginalis consists of a syncytium, perikarya and four kinds of secretory bodies, viz. electron-dense granules, moderately electron-dense vesicles, electronlucent vesicles and large multivesicular bodies occurring in the ratio of 83:50:40:1. Microvillus-like structures, finger-like projections and a thin coat of glycocalyx occur on the tegument. In contrast, the syncytium of the clamp is relatively thin and irregularly folded, containing only three kinds of secretory bodies, viz. electron-dense granules, a few moderately electron-dense granules and several large electronlucent vacuole-like structures in the ratio of 15:2:5. Exocytosis of the electron-dense and -lucent vesicles is apparently prevalent both in the syncytium of the haptor and general body surface. Tegumental damages induced by natural mechanical forces appear to occur in some regions of the syncytium of the clamps/ haptor. Sclerites of the clamp are electron-dense and they are interconnected by the basal lamina, tendon and radial muscle fibres. Interstitial space is absent between the sarcolemma of adjacent muscle fibres of the clamp. Groups of neurons and non-myelinated nervous processes can be seen in the vicinity of the clamps. The axon is subdivided by invaginations of the neurolemma. Presumed non-ciliated mechano-receptors occur on the body surface.