This draws an obvious dichotomy between marine and freshwater systems.
The ' prosobranch ' caenogastropods arose first in the sea and then moved into freshwater and onto land.
Human infections with the lung fluke are acquired by eating raw or undercooked freshwater crabs containing live metacercariae.
A slab of freshwater ice formed the smooth top of a billiard table made of ice blocks, with pockets and cushions crafted out of walrus-hide.
The available evidence on freshwater monogeneans supports the notion that monogenean infections are relatively more intense among hosts in which monogenean species richness is high.
This composition does not mean that marine hosts are only infected by marine parasites, freshwater hosts only by freshwater parasites, and so on.
Here they were maintained live in recirculating freshwater aquaria prior to their examination.
Two groups were maintained as controls and were examined after short-term or long-term transfer to laboratory freshwater.
