How does it look like?
It is a small nudibranch, at most about 2 centimeters long. It is reddish/orange in color, with an oval dorsum (or noto), on which are numerous conical tubercles of different sizes. In the middle of the back there is usually a perpendicular band of a light mottled color, quite characteristic. The dorsum or noto is oval with numerous conical tubercles of different sizes. The rhinophores are thick and have 8 or 9 lamellae. The gills have 8 or 9 unipinnate blades and are arranged in a circle around the anus. The oral tentacles are not well defined.
Where does it live?
It is a Mediterranean species cited from Gibraltar to Catalonia or the Balearic Islands. It is usually found looking under the stones.
How does it feed?
It feeds on encrusting sponges, most probably of the Hemymicale columella species, on which it has often been found.
How does it reproduce?
It is hermaphroditic and probably, like most nudibranchs, exchanges sperm when two individuals are positioned opposite each other on their right side to connect their seminal ducts.
Is a confusion possible?
This species is very similar to its congener Aldisa smaragdina, although this second species lives ususally at the Atlantic Ocean. Morphologically, Aldisa smaragdina has fewer gill blades, 5 to 6, and these are white on top, when in Aldisa banyulensis they are completely red. Aldisa smaragdina also has the dorsal whitish spot further back and the size of the tubercles surrounding the gills and rhinophores is smaller. Aldisa banyulensis lays fewer eggs. Finally Aldisa smaragdina seems to feed on the sponge Phorbas fictitius.
· This is a species with a great lack in data. Not much is known about its life cycle.
Phylum: Mollusca, Class: Gasteropoda, Subclass: Opistobranchia, Order: Nudibranchia, Family: Dorididae, Genus: Aldisa