One of the many predators the reefbuilder crabs must defend their livestock from is the sonic sucker. Sonic suckers are false fish with one skull formed into a parabolic dish (though some species make use of the fusion of two or three skulls). The sucker places this dish on the surface of a shell and bombards it with sound until it finds the right frequency to crack it open. Once this is accomplished, it sucks the meat out through the hole. While in most species it is the parabolic head with the mouth and the forward head with the eyes, some species retain a second mouth in the forward head for chewing weeds. While suckers are too fast for crabs to catch, breaking open a shell can take a long time, allowing the crabs to chase them off. Unfortunately some sucker species have graspers to carry a meal away with them while they swim.
Written by Daniel Noe, ChampionOfTheGalaxy.com