Surface ultrastructure of Metagonimus miyatai metacercariae and adults

Abstract

A scanning electron microscopic study was performed to observe surface ultrastructures of excysted metacercariae and adults of Metagonimus miyatai. Metacercariae were collected from the scale of the pale chub (Zacco platypus), and adult flukes were harvested 1-4 weeks after infection to rats. In excysted metacercariae, the oral sucker was devoid of tegumental spines and had type I and type II sensory papillae. Anteriorly to the ventral sucker, spines were dense and digitated into 5-7 points, whereas near the posterior end of the body spines were sparse and digitated into 2-3 points. In one-week adults, 7 type II sensory papillae were arranged around the lip of the oral sucker, and at inner side of the lip one pair of small and two pairs of large type 1 sensory papillae were seen on each side. The distribution of tegumental spines was similar to that of metacercariae, but they were more differentiated with 9-11 pointed tips. In two- to four-week old adults, the surface ultrastructure was nearly the same as in one-week old adults, however, sperms were frequently seen entering into the Laurer's canal. Conclusively, the surface ultrastructure of M. miyatai was generally similar to that of M. yokogawai, however, differentiation of tegumental spines and distribution of sensory papillae around the oral sucker were different between the two species, which may be of taxonomic significance.

Surface ultrastructure of the adult stage of Acanthotrema felis (Trematoda: Heterophyidae)

“…For the case of H. continua, the number of digitations in the tegumental spines of the anterior body increased from 10-14 to 15-17 as the worm matured from a metacercaria to the adult fluke (Hong et al, 1991). Similar findings have been reported in other heterophyid flukes (Chai et al, 1998(Chai et al, , 2000. However, information on the surface ultrastructure of the metacercariae and juvenile worms of A. felis are, at present, unavailable, and the changing patterns of the tegumental spines according to the maturation of worms are unknown.…”

“…The tegument on the postero-dorsal surface, where the spines are long, but narrow, with 6-8 pointed tips. been observed in other heterophyid flukes (Køie, 1977(Køie, , 1992Lee et al, 1984;Taraschewski, 1984;Fujino et al, 1989;Hong et al, 1991;Chai et al, 1992Chai et al, , 1998Chai et al, , 2000Srisawangwong et al, 1997;Uga et al, 1998;Woo et al, 1998).…”

Tegumental ultrastructure of Echinoparyphium recurvatum according to developmental stages

“…In case of some intestinal digeneans, tegumental spines are enlarged and more pointed as the worm maturates (Køie, 1977;Lee et al, 1985;Hong et al, 1991;Chai et al, 1998Chai et al, & 2000. The aforementioned findings have been observed in some tissue migrating trematodes i.e., Fasciola hepatica (Bennett, 1975), Paragonimus westermani (Lee et al, 1981) and Paragonimus iloktsuenensis (Lee et al, 1989).…”

Tegumental Ultrastructure of Adult Gynaecotyla squatarolae (Digenea: Microphallidae)

“…This may reflect limitations of light microscopy. However, the presumed Laurer's canal of our specimen was different from that of Metagonimus miyatai, which was surrounded by several layers of sphincter-like structures, and numerous sperms were entering through it [15]. Since no sperm was observed near the opening of the present specimen, it is suspected to be a vestigial Laurer's canal resulting from an absence of cross-fertilization in G. squatarolae.…”