Studies on larval trematodes infecting freshwater snails in Pakistan. VII. Echinostome cercariae

Three new echinostome cercariae parasitizing Lymnaea rufescens in Pakistan are described. Cercaria spinicephala n. sp. is characterized by a collar bearing 26 spines, arranged in an uninterrupted double row, five penetration glands on either side of the esophagus, cystogenous glands with rod-shaped contents, intestinal caeca reaching the posterior region of the body, an almost triangular excretory bladder, ascending excretory ducts enclosing refractile concretions, and a tail without a finfold. C. paraspinicephala n. sp. is furnished with 47 collar spines arranged in an uninterrupted double row, four pairs of penetration glands around the esophagus, an acetabulum larger than the oral sucker, a large, rounded excretory bladder, bunches of cilia in descending excretory ducts, and a thick cytoplasmic covering around the tail. C. heterolophoformis n. sp. is characterized by 25 collar spines arranged in an uninterrupted double row, a small prepharyngeal saccular structure containing bundles of refractile rod-like material, six pairs of large penetration glands laterally along the esophagus, an acetabulum larger than the oral sucker, a small rounded excretory bladder, numerous refractile concretions in the ascending excretory ducts, and a discontinuous caudal finfold.