Gastropods

Tylodina perversa – Yellow Tylodina / Yellow Umbrella Slug

Description

Tylodina perversa is a nudibranch belonging to the Tylodinidae family, with a yellow, rounded shell that resembles a small umbrella. Although it appears to have a shell, it is classified as a sea slug. It reaches a size of about 2–3 cm and is recognizable by its yellow to yellow-brown coloration and a flat, disc-shaped cover.

Diet

Tylodina perversa is a specialist feeder, consuming exclusively the sponge Aplysina aerophoba (gold sponge). During strong water movement, it often hides inside the sponge.

Lifestyle

• Habitat: It is found in the Mediterranean Sea and the northeastern Atlantic Ocean (up to the British Isles) in shallow waters up to about 40 meters deep.
• Distribution: In the Mediterranean and Eastern Atlantic, there are three similar species of the genus Tylodina: Tylodina perversa and Tylodina rafinesquii in shallow water, and Tylodina duebenii in deeper water.
• Reproduction: It lays spiral-shaped egg ribbons.

Fun Facts

• Pseudo-Shell: Although it looks like a snail with a shell, its "house" is primarily made of protein, not calcium carbonate, as in typical snail shells.
• Specialized Diet: It is specialized in feeding on the gold sponge and cannot survive without it, making it unsuitable for aquarium keeping.
• Scientific History: Originally described as Patella perversa in 1791, it was later classified under the genus Tylodina. In 2020, it was discovered that Tylodina perversa from the Mediterranean and Eastern Atlantic actually comprises two similar species, with Tylodina rafinesquii being recognized as a distinct species again.