White Aeolis

Overview

The White Aeolis (Favorinus branchialis) is a small, translucent nudibranch often found in association with the egg masses of other sea slugs. It is a specialized predator that thrives wherever other opisthobranchs are abundant, making it a frequent visitor to areas where these mollusks congregate to spawn.

Appearance

This species typically features a translucent white body adorned with opaque white pigment, including a distinct triangular patch on the head and diamond-shaped markings along the back. Its rhinophores are a key identification feature, characterized by a brown base, a noticeable swelling near the tip, and a white apex. The cerata are arranged in six or seven rows, and their internal color often shifts depending on the specific egg mass the individual is currently consuming.

Feeding

Favorinus branchialis feeds almost exclusively on the egg ribbons of other sea slugs, such as sea hares and various nudibranchs. Because it derives its coloration from its diet, the digestive gland visible within its cerata can change hue as it moves between different food sources. While adults focus on these egg masses, juveniles have been observed feeding on hydroids, such as those in the genus Obelia.

Distribution & habitat

This nudibranch is widely distributed across the Northeast Atlantic, ranging from the coasts of Norway and the British Isles down to the Mediterranean Sea and the Canary Islands. It is typically found in shallow, subtidal rocky environments, often remaining in close proximity to the egg masses it relies on for sustenance.