Berthella plumula, commonly known as yellow-plumed sea slug, is a gastropod mollusc usually found on rocky coasts in the infralittoral zone[1] and which can live up to 30m depth.

[2] Berthella plumula is an oval-shaped sea slug with an internal shell, which can be up to 30 mm (1.2 in) long.

The body is up to 60 mm (2.4 in) and has a cream to orange colour and often displays reticulate markings.

The head is flat and a large oral veil lies between the propodium and the mantle.

[4] Berthella plumula is a slow moving predator which scrapes its radula on rocks to feed on colonial ascidians of the genus Botryllus as well as on Oscarella sponges.