An unusual midwater nudibranch

Cephalophyge trematoides is a pelagic nudibranch, meaning that it spends its entire life swimming or drifting in the ocean and never touching the bottom. It has a flat, transparent body and swims by undulating its entire body. It has been observed attaching to siphonophores and eating tentacles, and eventually whole colonies of siphonophores. Juvenile Cephalophyge parasitize medusae, by attaching to the inner bell and sucking up the medusa’s radial canals and manubrium. This video shows an adult Cephalophyg