Phyllodesmium horridum, the coral nudibranch, is a species of sea slug, specifically an aeolid nudibranch. It is a marine gastropod mollusc in the family Facelinidae.
This species is found around the South African coast from False Bay to Sodwana Bay, intertidally to at least 30 m.[1] It has been erroneously reported from Australia and Japan due to confusion with Phyllodesmium serratum.
Around the South African coast, the coral nudibranch is typically between 30 and 40 mm[2] in total length. It is a slender pale-bodied aeolid with long paired pinkish cerata. The cerata have a bluish-white stripe running down their length, as does the body. The rhinophores are smooth. This species contains no zooxanthellae.[3]
Phyllodesmium horridum feeds on sea fans (gorgonians) of the genus Melitodes (family Melithaeidae). It has also been reported to feed on gorgonians of the genus, Acabaria (also family Melithaeidae).[3] The egg ribbon is a gelatinous mass with many small white eggs.[4]