Molecular Description of Macroorchis spinulosus (Digenea: Nanophyetidae) Based on ITS1 Sequences

We performed a molecular genetic study on the sequences of 18S ribosomal RNA (ITS1 region) gene in 4-day-old adult worms of Macroorchis spinulosus recovered in mice experimentally infected with metacercariae from crayfish in Jeollanam-do Province, Korea. The metacercariae were round, 180 µm in average diameter, encysted with 2 layers of thick walls, but the stylet on the oral sucker was not clearly seen. The adult flukes were oval shape, and 760-820 µm long and 320-450 µm wide, with anterolateral location of 2 large testes. The phylogenetic tree based on ITS1 sequences of 6 M. spinulosus samples showed their distinguished position from other trematode species in GenBank. The most closely resembled group was Paragonimus spp. which also take crayfish or crabs as the second intermediate host. The present study is the first molecular characterization of M. spinulosus and provided a basis for further phylogenetic studies to compare with other trematode fauna in Korea.

Developmental surface ultrastructure of Macroorchis spinulosus in albino rats

Developmental surface ultrastructure of Macroorchis spinulosus was studied by scanning electron microscopy. One-day-old juvenile fluke was leaf-shaped and bent ventrally. Body surface was covered densely with peg-like spines and with cobblestone-like cytoplasmic processes. Ciliated sensory papillae were concentrated around oral sucker. Several unciliated sensory papillae occurred equidistantly on oral sucker and acetabulum. The ciliated papillae appeared in two longitudinal lines symmetric bilaterally on dorsal surface. On adult flukes, tegumantal spines became wider in middle of the body surface. The cytoplasmic processes differentiated into more fine velvety form. It is likely that the differentiated fine cytoplasmic processes are an increased absorptive surface to adult M. spinulosus. It is suggested that single pointed tegumental spines on anterior half of the body may be supportive for this fluke to migration.