Similar to the intestine, the bloodstream is a habitat of high current flow that can dislodge parasites. However, it is a closed system and so dislodgment does not have consequences nearly as serious as those for intestinal parasites. There are relatively few morphological features of blood parasites that can be considered as adaptations for attachment. Most are protozoans and simply "go with the flow"
Schistosomes have two adaptations for attachment that are useful in the bloodstream. The male has a large, pedunculate acetabulum. The gynecophoric canal of the male provides a refugium for the female, enabling these dioecious trematodes to remain in proximity to their mate.
