Meeting Abstract
Adult graceful decorator crabs (Oregonia gracilis) decorate by attaching pieces of algae, sponge, or other items from their habitat onto hooked setae, but decoration behavior has not previously been studied in juvenile crabs. Decoration is thought to provide camoflauge in the adult habitat, suggesting that decoration behavior might begin soon after settlement into that habitat. Alternatively, juvenile crabs may rely on crypsis initially and begin decorating once they are too large to hide effectively. SEM revealed that hooked setae were absent in megalopae, but present in first instar juveniles and adults. Megalopae did not exhibit any decorating behaviors, but first instar juveniles actively and profusely decorated with organic debris. Thus, the onset of decorating occurs very soon after settlement into the adult habitat, at the molt from megalopa to first instar juvenile. Crypsis may also be a priority: in a habitat choice experiment, megalopae and first instar juveniles chose the most structurally complex habitat (erect bryozoans) over sponges or red algae. Although decorating behavior begins immediately after settlement, it changes over time: juvenile and adult crabs chose different materials for decorating. This may be the result of size-related differences in which materials make for the most effective camoflauge, or it may be the result of biomechanical differences in the material handling ability of adults and juveniles. We conducted preliminary investigations on material handling behavior in adult crabs, and propose several testable hypotheses regarding size-related changes in material handling ability and preference in decorator crabs.
