Cool Inverts


Enjoy the wonderful world of invertebrates, which comprise 95 percent of all living animal species.  Featured invertebrates on this page will change as time allows.

Crustaceans that Replace Organs

The crustacean order Isopoda (the pillbugs, sowbugs, gribbles, etc.) includes ~10,000 described living species, split more-or-less evenly between terrestrial/freshwater and marine environments.  The largest species live in the sea, where they can reach ~2.5 ft in length (Bathynomus).  One of the largest isopod families is Cymothoidae, which are ectoparasites on marine and freshwater fishes around the world.  Cymothoid mouth parts are specialized to “suck” blood from their host fish.  Some cymothoids live on or under (encapsulated) the skin, whereas others inhabit the gill chamber or mouth.  All are protandric hermaphrodites, developing first as males and then changing sex to become females.  One of the most unusual cymothoid species is Cymothoa exigua that, in the Gulf of California, parasitizes a range of fishes, one of which is the spotted rose snapper Lutjanus guttatus.  Uniquely, the isopod drains so much blood from the snapper’s tongue while feeding, that the tongue degenerates and disappears.  (The tongue in fishes is little more than an extension of the basihyal bone.)  This isopod remains attached to the muscular tongue stub with its hooklike legs, and the snapper then utilizes it as a “replacement tongue,” apparently continuing to feed and respire normally.  This phenomenon appears to be the only known example (in animals) of a functional replacement of a host structure by a parasite.  In 2013 a second occurrence of this phenomenon was documented from the Indian Ocean, where the parasite species is Cymothoa borbonica and the host fish the large-spot pompano Trachinotus botla (although there have been several erroneous reports from other species and localities in the world).   Brusca & Gilligan 1983 Tongue Replacement.pdf