Parasitism of Placobdelloides siamensis (Oka, 1917) (Glossiphoniidae: Hirudinea) in Snail-eating Turtles, Malayemys spp., and the effects of host and aquatic environmental factors

寄生于食螺龟属（Malayemys spp.）的暹罗蛭（Placobdelloides siamensis (Oka, 1917) (舌蛭科：蛭纲)）及其宿主和水生环境因素的影响