OPISTHORCHIS-VIVERRINI - CHANGES OF THE TEGUMENTAL SURFACE IN NEWLY EXCYSTED JUVENILE, 1ST-WEEK AND ADULT FLUKES

Opisthorchis viverrini: changes of the tegumental surface in newly exc ysted juvenile, first-week and adult flukes. International Journal for Parasitology 23: 829-839. The tegumental surface of the newly excyste d juvenile, first-week and adult stages of a human liver fluke, Opisth orchis viverrini, was studied by scanning electron microscopy. The sur face of the newly excysted juvenile is characterized by circumferentia lly arranged ridges alternated with troughs which bear rows of spines encircling the body. These spines are characterized by the shapes of t heir edges: the first type with serrated edge appears on the anterior part, and the second type with single sharp edge appears on the middle part. There are no spines on the posterior part of the body. Three ty pes of presumed sensory papillae are present: type A is a single small cone-shaped ciliated papilla; type B is a group of ciliated papillae on a common dome-shaped base; and type C is a large papilla with nonci liated bulb. Type A papillae are scattered evenly on the surface but a re more concentrated around the oral and ventral suckers, as well as t he excretory pore. Pairs of both type A and B papillae are located in rows along the lateral surfaces of the body. Type C papillae are locat ed solely on the lip of the ventral sucker. In the first-week fluke th e tegumental surface appears corrugated and covered with short develop ing microvilli, and spines are mostly lost. In the fully-grown adult f luke the surface appears highly corrugated with wave-like folds encirc ling the body which are covered in turn with closely packed stubby mic rovilli. Microvilli are more numerous and are taller on the ventral th an on the dorsal surface. Among microvilli on the surface of both olde r stages three types of sensory papillae as in the newly excysted juve nile were observed, but they are of larger sizes. The number of type A papilla increases whereas that of type B papilla decreases during mat uration. The distribution of papillae in both stages is similar to the newly excysted stage.