Doridunculus unicus is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Onchidorididae.

[1] Doridunculus unicus was first discovered in deep-sea basin of the Sea of Japan (depth 3000-3620 m).

The absence of notal crests, asymmetricalnotal lobes, and characteristics of the radula anatomy distinguish Doridunculus unicus from the two other known specimens of the species.

(Campanulinidae) and dwells in large aggregations of their colonies (numerous broken fragments of Egmundella sp.

[2][3] Unicus (Latin) refers to three distinct characteristics: the history of discovery and description, asymmetrical notal lobes, and living with and feeding on hydroid.