New records of Planes crabs associated with sea turtles in Africa and adjacent waters

Abstract

Crabs of the genus Planes (family Grapsidae) live on floating debris and pelagic animals and spend their lives rafting at the surface of the open ocean. Among living substrata, Planes minutus is frequently found associated with sea turtles. However, prior to this study, crabs had never been documented on sea turtles in continental Africa or in the western Indian Ocean. We found P. minutus associated with olive ridley sea turtle Lepidochelys olivacea nesting and foraging/pre-nesting in Gabon, and with loggerhead Caretta caretta and green sea turtle Chelonia mydas foraging off the east coast of South Africa, as well as loggerheads nesting in Cape Verde and loggerheads foraging off Réunion. No crabs were found on nesting loggerheads surveyed in Oman. We integrate these new findings with a review of all known records of Planes–sea turtle interactions in the Atlantic and Indian oceans and the Mediterranean Sea, to better understand the geographic distribution and ecological characteristics of such associations.