Meeting Abstract

P1.14  Friday, Jan. 4  Decoration preference and habitat selection in early stage juveniles and megalopae in the decorator crab Oregonia gracilis HEIN, S.R.*; JACOBS, M. W.; Mcdaniel College; Mcdaniel College srh001@mcdaniel.edu

Often referred to as decorator crabs, many species from the family Majoidea (Decapoda; Brachyura) adorn their bodies with decorations by attaching pieces of algae, sponge, or other items from their habitats onto hooked setae. Oregonia gracilis is a wide ranging cold water Pacific decorator crab. We investigated carapace morphology of and habitat selection by megalopae and juveniles, as well as juvenile decoration preferences. Hooked setae were absent in megalopae, but appeared in first instar juveniles, and were arranged in distinct sparse rows of single setae. As the crabs progressed in size the number of rows increased and setae began to occur in clusters. The young crabs began to decorate during their first instar. When presented with a choice of three materials commonly found attached to adults (sponges, erect bryozoans, and red algae), juveniles preferred to decorate with unidentifiable debris found free floating in the water or stuck to offered decorating materials. The sparsely arranged setae or weak chelae of very young juveniles may make it easier for the juveniles to attach debris over other more robust materials. When given habitat choices using the same aforementioned materials plus a mixture of all three, both megalopae and juveniles favored bryozoans. We think this behavior may be related to crypsis. Compared to other potential habitats, erect branching bryozoans have a great deal of structural complexity and a large attachment of debris for decoration, both qualities that could be exploited by the young crabs who likely rely on crypsis as a means of survival.