Agonistic interactions in most animals reflect individual social experience and nutritional status. Crustaceans establish social hierarchies in which dominant individuals tend to be largest, most aggressive, and have the greatest access to resources such as mates, shelter, and food. Subordinates, on the other hand, are smaller and lack access to resources. However, to become dominant, individuals must grow, a process that requires nutrients. Crustacean grow through a process known as molting, where animals shed their external skeleton and rebuild a larger carapace. During molt, animals are very vulnerable to predators and potential competitors. Thus, an animal must balance the potential benefit of growth with the risk of injury resulting from agonistic interactions during molting. In this study we asked how being in a social group influences molting behavior. The crayfish Orconectes obscurus were isolated for 7 days and then placed into either an individual tank or into a tank with 2 same-sex crayfish. Interactions in group tanks were recorded and analyzed to determine social status of each individual. Animals were observed daily for 30 days to note movement patterns and molts. Although dominant individuals typically have greater access to limited resources required for molting and would theoretically molt sooner and more frequently than subordinates, when food was equally available to all individuals, subordinates actually molted sooner and more frequently than dominant individuals. Additionally, there was a seasonal effect in which the molt rate and frequency was greatest in the summer. These findings suggest that sociality and seasonality strongly influence molting behavior in crustaceans.
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Vol. 88 • No. 1