This animal is pretending to be a different slug, and it hides the one part that would give it away.
Wart slugs are the untouchable ones on this reef: hard, ridged, loaded with toxins through the whole body, and left alone by everything. This species is not a wart slug and is not defended the same way. It is an ordinary soft dorid that has evolved the wart slug's look, down to the ridged black-and-pale back, and it gets the protection without the chemistry.
The detail that makes it remarkable is the gills. Every dorid carries a plume of them standing on the back; phyllidiids are the family that lost theirs entirely and breathe under the mantle rim instead. A mimic with a gill rosette waving on its back would be advertising exactly the wrong thing, so this one keeps the plume folded down and out of sight. The disguise is not only the paint job. It includes concealing an organ.
Which is presumably why it went unnamed until 2020. An animal that looks like a wart slug in every photograph gets filed as a wart slug, and the mimicry had to be seen through before anyone realized there was a second species there at all.
It is three centimeters, known from the Egyptian coast and the Gulf of Aqaba, and its name says what it does: hypocrita, the pretender.
- looks like a wart slug: hard-looking ridged back in black and pale patches
- gills usually hidden, which is what a wart slug would look like
- softer and lower than a real phyllidiid when seen from the side
- found in the Red Sea and nowhere else
