Size up to 270 mm. Large sea slug presenting the typical, wing-like parapodia that are characteristic of the genus Aplysia. Internal shell present. Color very variable, blackish, brown, green, yellow, with white and/or darker mottlings. Internal shell chitinous, translucent light-brown.
Sea hares are active swimmers using the parapodia to perform wing-like motions, and are voracious macro-herbivores, consuming large quantities of sea weed on a daily basis. This species was listed previously in this guide as Aplysia fasciata Poiret, 1789, but this is an eastern Atlantic species.
The Mottled Sea Hare may be distinguished from the Atlantic Black Sea Hare, Aplysia morio (A.E. Verrill, 1901), among other features, by the usually lighter coloration and smaller size. The sea hare in the photo was collected by R. Mensch in February 2017.