Tylodina perversa (Gmelin, 1791)

Description

A notaspidean with a limpet-like shell. The shell is composed mainly of conchiolin (protein) rather than calcium carbonate and is yellowish-brown to nearly black, flat and cap-shaped. The body is bright yellow, reaching up to about 7 cm in length, making this a comparatively large species. The soft body extends out from beneath the shell, giving an umbrella-like appearance.

Distribution

North-east Atlantic (the British Isles, Portugal, Canary Islands, Madeira, Azores, Cape Verde) and throughout the Mediterranean.

Etymology

The specific epithet perversa is Latin for "reversed, contorted", probably in reference to the unusual shell coil and form, which differs from typical gastropod patterns.

Remarks

Known in English as the Yellow Umbrella Slug. Feeds exclusively on the sponge Aplysina aerophoba. A defining family character is the largely proteinaceous (rather than calcareous) shell.

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References

• Tylodina perversa (genus Tylodina), Rafinesque C.S. (1814). Précis des découvertes et travaux somiologiques de Mr. C.S. Rafinesque-Schmaltz entre 1800 et 1814. Royale Typographie Militaire, Palerme. 56 pp.