How does it look like?
Orange or brownish coloured opisthobranch, depending on the diet. On the back it has 14 to 16 rows of cerata (tube-shaped protuberances typical of nudibranchs), the first rows of which are shorter and paler. The tips of the cerata are whitish or yellowish, especially in the first row, where the digestive tube reaches only half of the total length of the cerata.
Where does it live?
It is a mainly found under rocks, at shallow depths or in intertidal environments (waterlogged areas permanently covered with water). Geographically it can be found throughout the Mediterranean and the British Isles.
How does it feed?
Like almost all mollusks, it has a radula (toothed tongue) through which it can fragment and crush food before swallowing it. Its diet is based mainly on actinians (cnidarians-anemones), mainly Cereus pedunculatus.
How does it reproduce?
It has a direct development, so there is no planktonic (swimming) veliger phase. Individuals are hermaphrodites (they have reproductive apparatus of both sexes) and reproduce by cross-fertilization (one individual fertilizes another and the other way around, at the same time).
Is a confusion possible?
Confusion is easy with Spurilla neapolitana. The most direct way to recognize them and distinguish the two species is through the cerata. Aeolidiella alderi has them more numerous, thin and smooth, while Spurilla neapolitana has them wavy, fewer and thicker.
· An interesting feature of many nudibranchs is the ability to acquire defense systems through their prey. Cnidarians have a special type of cells that they use to defend themselves, the cnidocytes, which nudibranchs like Aeolidiella alderi are able to ingest and incorporate into their own defenses without destroying them. This gives them a stinging property similar to that of jellyfish and corals.
Phylum: Mollusca, Class: Gasteropoda, Subclass: Opisthobranchia, Order: Nudibranchia, Suborder: Aeolidiina, Family: Aolidiidae