A morphological and histochemical study of the gland cells of a cercaria referable to the genus Acanthoparyphium (Trematoda: Echinostomatidae)

Abstract

A cercaria referable to the genus Acanthoparyphium encountered in Cerithidea cingulata has been named as Cercaria bengalensis II. The present paper is the first report on the glandular complex in this genus. Our studies revealed the presence of different types of gland in the body and tail of Cercaria bengalensis II. Morphologically, three types of gland cell were apparent: penetration, cephalic and cystogenous glands. Histochemically, three types could be discerned as cystogenous glands: dorsal granular, dorsal vacuolated and ventral gland cells. Altogether five types of gland cell occurred. During the intraredial stages, a layer covering the tegument of the cercaria originated from the secretions of the ventral gland cells. In addition to this layer, a second layer underlying it was formed by secretions of the dorsal vacuolated cells. The secretions of the penetration glands contained proteins such as keratin, elastin- and collagen-like substances, and carboxylated and neutral mucopolysaccharides. The cephalic glands contained only keratinized proteins and traces of non-sulphated acid mucopolysaccharides. Dorsal granular cells had the task of secreting keratin, disulphides, sulphydryls, elastin- and collagen-like substances as protein components and also sulphated and carboxylated acid mucopolysaccharides and traces of neutral mucopolysaccharides. Dorsal vacuolated cells behaved like dorsal granular cells, but did not secrete neutral mucopolysaccharides. Disulphide-containing proteins, lipids and phospholipids were also present. The ventral gland cells consisted only of strongly sulphated acid mucopolysaccharides and neutral mucosubstances, with no proteins.