9615461 CUNNINGHAM Hermit crabs are best known for using empty snail shells as shelters. Most morphological features that define hermit crabs as a group seem to be adaptations to the asymmetrically coiled shell. A surprising number of species, however, use objects other than snail shells for shelters, or use no shelter at all. These hermit crabs tend to be more symmetrical than their shell-using relatives, and those that use no shelters are also often "carcinized"; that is, the abdomen is reduced and tucked under a wide, heavily armored carapace. Such crabs may not be recognized as hermit crabs, but may instead be wrongly placed in other crab groups. The lack of a reliable phylogenetic history has made it impossible to resolve long-standing questions concerning the evolution of shell use, asymmetry and carcinization in hermit crabs. In this collaborative research project, Cliff Cunningham (molecular sequences) and Alan Harvey (morphology) will integrate extensive morphological and molecular data to generate a robust phylogeny for the hermit crabs and their allies (i.e., the Anomura). With this phylogeny, Cunningham and Harvey will determine 1) how many times anomuran crustaceans independently adopted the shell-using habit; 2) whether the carcinized morphology of nonshelter-using hermit crabs evolved from the asymmetrical morphology of shell-using hermit crabs, or vice versa; 3), which features of both the carcinized and asymmetrical morphologies are influenced by the presence and type of shelter used by hermit crabs.
