Scanning electron microscopy of newly excysted metacercariae of Paragonimus westermani-like, Nakhon Nayok, Thailand.

Scanning electron microscope (SEM) observation of surface structure was done on newly excysted metacercariae of Paragonimus westermani-like (Nakhon Nayok, Thailand). The surface of the body was covered with numerous single-pointed tegumentary spines, large dome-shaped papillae, small one with a pit, and small one with a smooth surface were situated around the suckers. There were 27 to 30 of the small dome-shaped papillae with a pit around the oral sucker and 10 to 13 of the small ones with a smooth surface around the ventral sucker. The present report is the new record of excysted metacercariae of P. westermani-like (Nakhon Nayok, Thailand) by SEM.

Eggshell morphology of the small eggs of human trematodes in Thailand.

Light and scanning electron micrographs of Opisthorchis viverrini, Haplorchis taichui, H. pumilio, A Phaneropsolus bonnei, and Prosthodendrium molenkampi eggs were studied. Under light microscopy. O. viverrini eggs had rough eggshells and prominent shoulders. H. taichui, H. pumilio were similar in shape and had smooth eggshells and prominent shoulders. H. pumilio eggs were bigger than H. taichui eggs. P. bonnei and P. molenkampi eggs had smooth eggshells and indistinct shoulders. P. bonnei eggs were thinner and bigger than P. molenkampi eggs. Some deformed eggs of O. viverrini and Haplorchis sp. were found and they had no embryos and indistinct opercula. Under scanning electron microscopy, O. viverrini eggs looked like musk-melon skin; they had prominent shoulders and long knobs. H. taichui eggs had curly, thread-like ridges and prominent shoulders and knobs. H. pumilio eggs had streched ridges, like Chinese bitter mormodica, and prominent shoulders. P. bonnei and P. molenkampi eggs had smooth eggshells and small shoulders and knobs.

Scanning electron microscopy of adult Echinostoma malayanum.

Scanning electron microscopy observations of E. malayanum adult obtained from small intestines of infected rats was made. The number of collar spines were 41. The features observed were a pair of corner spines (3 oral and 2 aboral) total 10; a pair of lateral collar spines (10 spines each side); total 20; dorsal collar spines (5 oral and 6 aboral) total 11. Sensory papillae were found more densely situated on the circumoral disc around the oral sucker and on the ventral sucker. Other sensory organs, dome shaped, found only on the circumoral disc. The scales appear mainly on the ventral surface. The microvilli are present on the tegument where the scales occur, while the other part of dorsal side had pitted tegument.