[Scanning electron microscopical observations on Pagumogonimus skrjabini metacercaria and juveniles]

The present paper reports on the results of scanning electron microscopical observations on seven excysted metacercariae and twelve juveniles of Pagumogonimus skrjabini. The former were from the naturally excysted metacercariae in fresh water in Ningquang District of Shaanxi Province and the latter were collected from the dogs and rats experimentally infected with metacercariae from the District mentioned above. Both excysted metacercariae and juveniles have tegumental ridges or folds on the surface of the body. The anterior two-thirds of the body surface are covered with many dome-shaped sensory papillae. There are rings of this kind of papillae on the rim of oral and ventral suckers. The papillae being obviously in decreasing number in the 30-40-day-old juveniles and adult worms. Except for the suckers and excretory pores, the whole body surface of the metacercariae and the juveniles are covered with posteriorly pointing tegumental spines which are relatively denser in the forebody than in the hindbody. Spines around the oral sucker are bayonet-shaped, and those on the rest part of the body surface are basically chisel-shaped. The authors considered it important that spines of P. skrjabini can be arranged singly or in groups.