Natural history update of the orange-clawed hermit crab Calcinus tibicen (Herbst, 1791) (Anomura: Diogenidae) in the Southwestern Atlantic

Abstract The Calcinus tibicen (Herbst, 1791) is one of the most widespread species of hermit crab in the Western Atlantic. However, important gaps remain in our knowledge of its ecology, distribution, and natural history in the South Atlantic. In this study, we present updated information on the geographic distribution and natural history of C. tibicen , including new records of its habitats, shell occupancy, and symbiotic associations. Data on its distribution, habitat use, and shell occupancy were obtained from field collections along the Brazilian coast. Additional occurrence records were compiled from literature reviews and public databases. In total, we recorded 1,306 occurrences, including 497 new records (417 in the North Atlantic and 80 in the South Atlantic). The species inhabits diverse microhabitats and is associated with several marine organisms, including anemones, corals, barnacles, mussels, sponges, zoanthids, and macroalgae. Specimens from Brazilian ecoregions primarily occupied gastropod shells, and epibionts were frequently recorded on these shells. Additionally, we present the first documented cases of C. tibicen associations with anemones and chitons. These findings expand our knowledge of this species' natural history and ecological interactions in the South Atlantic.