Intertidal Organisms EZ-ID GUIDES


on this species


Diodora aspera (Rough keyhole limpet)

photo of keyhole limpet
Copyright © 2005 Mary Jo Adams


Viewed from above, the rough keyhole limpet is oval in shape with a circular hole marking the apex, just anterior to the center.   Course ribs radiate out from the hole.   It reaches a length of about 2 ¾ inches.   The animal is gray or white, sometimes with darker lines. The actual surface of the animal may however be obscured due to the presence of encrusting algae or other organisms.


In spite of its common name, the rough keyhole limpet is not a true limpet but is more closely related to abalones.   Its gills are more primitive than those of true limpets and water circulation through the animal is also different. In addition, unlike limpets, which tend to be herbivores, this species prefers a carnivorous diet, feeding more on encrusting sponges and bryozoans than on algae.   It is preyed on by several species of sea stars.


Many keyhole limpets carry the commensal scaleworm Arctonoe vittata up under its shell in the mantle groove.   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.

This page was created by Mary Jo Adams on 12/5/05.



photo of rough keyhole limpet

photo of rough keyhole limpet


image of rough keyhole limpet with commensal worm