Description: A translucent white nudibranch with small tubercles and specks of white and/or yellow pigment on its dorsum. An opaque pale yellow ridge runs down the middle of the back to the tip of the tail. There is a transparent patch that is situated just behind the branchial plume, this looks like a small pore on the animals back. The lamellate rhinophores have a yellow tinge, the oral tentacles are dorso-ventrally flattened. This species may reach a length of 27mm.

Habitat: Juveniles feed on bryozoans, especially Alcyonidium diaphanum, but the adults feed on ascidians, especially Diplosoma listerianum and Dendrodoa grossularia.

Distribution: Distributed from north west Spain to the Faeroes. A common species all round the British Isles both on shore and in the shallow sublittoral, it has been recorded at depths down to 120m.

Key Identification Features:

• White animal with reduced thin frilly mantle rim and tail extending at rear.
• Front of head with oral tentacles visible from above.

Distribution Map from NBN: Okenia nodosa at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Okenia nodosa at iNaturalist World Species Observations database.

WoRMS: Okenia nodosa at World Register of Marine Species. Accepted name: Okenia nodosa (Montagu, 1808). AphiaID: 1723483.

Classification: Biota; Animalia; Mollusca; Gastropoda; Heterobranchia; Euthyneura; Ringipleura; Nudipleura; Nudibranchia; Doridina; Doridoidei; Onchidoridoidea; Goniodorididae; Goniodoridinae; Okenia