Philometridae is a family of nematodes belonging to the order Rhabditida.

[1] All Philometridae are obligate tissue parasites of fish.

[2] First-stage larvae are ejected into the water, and develop to the third stage if they're eaten by a cyclopoid.

Once the copepod is eaten by a fish, the larvae develop into adults and mate.

Pregnant females migrate to a final site just under the fish's skin, in the swim bladder, or in the coelom; males die soon after mating and in many Philometridae species they have never been described.