Fine Structure of the Cuticle of the Cercaria of Acanthatrium oregonense (Macy)

Abstract

The integument of the cercaria of Acanthatrium oreganense was studied by means of electron microscopy and histochemistry. The ultrastructure of the cuticle varies in different regions of the body. The body cuticle is characterized by the presence of fibril-containing vesicles in the syncytial cytoplasmic layer. These vesicles occur in the sucker in great density, but are absent from the tail cuticle. Instead there are small elongate cavities along the periphery of the tail cuticle. These structural differences have been correlated with histochemical findings. Chemically the body cuticle and sucker may be differentiated from the tail cuticle by the presence of mucopolysaccharides. The subcuticular layer of the body has a concentration of glycogen. Only a few workers have investigated the ultrastructure of trematode larval stages. Kruidenier and Vatter (1960) studied the cercaria of Schistosoma mansoni, limiting their discussion to the musculature of the tail. The cercaria of Himasthla quissetensis was studied with some reference to the integument (Cardell and Philpott, 1960; Cardell, 1962). The only work to focus specifically on the integument of cercariae is a study of the histogenesis of trematode cuticle from the sporocyst stage to the adult trematode, made by means of the electron microscope (Bils and Martin, 1966). Their discussion of one strigeid and three echinostome cercariae did not include descriptions of the tail and sucker. A more recent paper by Rees (1966) in this area briefly describes the ultrastructure of the integument of the redia of Parorchis acanthus. Axmann (1947) did the first studies localizing glycogen deposits in various larval stages and in the adults of three schistosomes. Her work has been continued in investigations of the histochemistry of larval trematodes and their effects on the pathology of the molluscan intermediate hosts (Cheng, 1963a, b; Cheng and Snyder, 1962, 1963). The purpose of this investigation was to provide more detailed information about the structure of the cercaria. Such an investigation would provide valuable information about the host-parasite relationship. MATERIALS AND METHODS Naturally infected snails, Oxytrema siliqua (Gould), were collected from Oak Creek near Received for publication 28 November 1966. * Present address: Department of Biology, California State College at Hayward. Corvallis, Oregon. Emerged cercariae were fixed in preparation for ultrastructural and histochemical study.