Cymothoa exigua is a powerful little crustacean, with seven pairs of legs tipped with spines, which help her anchor into the fish's mouth. However, the first step in the process is to use her five sets of jaws modified with a variety of ice-pick-like tubes to puncture the fish's tongue and suck out the fish's blood. This process, by the way, is not thought to be very pleasant for the fish.

As the isopod drains the fish's tongue of blood, the muscle itself atrophies and withers away. At this point, she grasps what remains of the tongue stub with three or four of her spined leg sets and digs in, functionally replacing the tongue all together.

As unpleasant as this is, these isopods generally don't kill their host. However, Cymothoa exigua does not survive well without a host.

"Without its host adult, fully mature isopods would not survive well, as it's an obligate parasite," says Wetzer. "It has lousy swimming capabilities and gravid females — females with eggs and juveniles in her pouch — are especially non-agile. This is in contrast to some species [of the same family of isopods] which are free-living and can occur in such large numbers that they can deflesh a fish or body entirely."