Rhodope placozophagus (Heterobranchia) a new species of turbellarian-like Gastropoda that preys on placozoans

Rhodope placozophagus nov. spec. from the western Gulf of Mexico that actively preys on placozoans is described. This white-translucent rhodopemorph was discovered on glass slides introduced in marine aquariums as part of an assemblage of small organisms including the vorticellids, ciliates, acoela, heliozoans and high populations of placozoans, which correlate with an abundance of this worm-like mollusk. When R. placozophagus comes into contact with placozoans, it immediately everts the anterior portion of the buccal bulb and sucks large portions of the disc-shape organism. The new species is likely to be a specialized predator since it was never observed chasing other microorganisms and especially because it can be reared for several generations while feeding exclusively on placozoans. It is known that the lipid granules called shiny spheres, located in the dorsal epithelium of Trichoplax, contain venoms and toxins that serve as an anti-predator defense. These properties can therefore be transmitted, at least transitorily, to a predator. Apart from one report of Riedl (1959) of Rhodope veranii preying on Trichoplax, no other predator-prey association has been described for placozoans.