Diodora aspersa is a sea slug belongs to the family Fissurellidae, the keyhole limpets. These limpets have a circular opening at the apical end of the shell, which serves both as an excurrent and anal opening.
The rough keyhole limpet is oval in shape with a circular hole marking.The animal is gray or white, sometimes with darker lines.This species prefers a carnivorous diet (encrusting sponges and bryozoans), than on algae. It is preyed on by sea stars.
Many keyhole limpets carry the commensal scaleworm Arctonoe vittata up under its shell. It is known, If attacked by a sea star, the scaleworm has been known to come to the defense of its host by biting the sea star's tube feet.