Meeting Abstract

P1.13  Friday, Jan. 4  Decoration preference in the Pacific crab Oregonia gracilis ODIERNO, J. A.*; JACOBS, M. W.; McDaniel College jao003@mcdaniel.edu

Decorator crabs (Brachyura: Majidae) attach resources from their environment to themselves throughout their lifespan. It is thought that this is a form of camouflage to protect the crab from predation. Some species of decorator crabs prefer to decorate with certain materials, while others are generalists and use whichever material is most opportune. Decorating is sexually dimorphic in Oregonia gracilis; adult males decorate sporadically while females and juvenile males decorate fully and consistently. To determine if the Pacific crab O. gracilis displays a preference in decorating material, crabs were collected, stripped of their existing decorations, and given either red algae, branching bryozoans, yellow Mycale sponges, or a mixture of the three. Male and female, and juvenile and adult O. gracilis preferred to decorate with the yellow Mycale sponges over the red algae and branching bryozoans. Although the reason for this preference is still unknown, we hypothesize that the sponge may be more easily manipulated by the crab, allowing for faster decorating time and in return a decrease in vulnerability time. An alternative hypothesis is that the sponge offers better chemical and physical defenses than the algae or the bryozoans. Unexpectedly, adult crabs decorated more with sponges when they were offered a mixture of materials, than when they were offered only sponges. The adult crabs may be inspired to decorate more when they are in a mixed environment.