June 4, 2010
June 4 - Lernaeocera branchialis
Life is about dealing with changes, but for Lernaeocera branchialis, some of those changes are pretty profound. This parasitic copepod starts out as a free-swimming nauplius, like other crustaceans. Then, it turns into a copepodid and seeks out an intermediate host, something slow and easy to find, like a flounder. It mates with an opposite-sex copepodid on this host and then sets off to find its final host, usually a cod or haddock. It then completely metamorphosizes into a large (4 cm), red, worm-like thing with a big egg sac and "antlers". Its head remains inserted into the gills of the fish where it feeds from the blood and pumps out new eggs.
The photo is from this site.