Parasitic isopods may seem strange and disgusting, but can also be fascinating creatures. There are a variety of parasitic isopods – a type we see frequently at MSI are the fish gill isopods (Elthusa californica and Elthusa vulgaris). They are small crustaceans that differ from free swimming isopods because of their hooked legs, which are adapted to grasping onto their host.
The isopod will climb into the gill chamber of a fish and use their mouth parts to attach to the fish’s blood-rich gills. Young fish can be quickly killed by feeding isopods. Adult fish are better able to handle being host to an isopod or two, but will not be as healthy as an isopod-free fish.
Parasites often have complicated, multi-host life cycles and can be really interesting to study (once you get past the “ick” factor!). Give parasites another look – starting with the fish gill isopod!