Schistosoma spp.

Schistosoma japonicum. Adult worms (hematoxylin stain, scanning power). Male and female adults are in copula. The schistosomes are the only trematodes of humans that have separate sexes. The long, slender female worm lies within the gynecophoral canal of the more robust male. Several small, dark-staining testes are present in the anterior portion of the male worm. These flukes live in blood vessels of the human host, as do all the other schistosomes. They measure 12 to 20 mm in length.