Meeting Abstract

106.2  Tuesday, Jan. 7 08:30  Social monogamy in Planes major, a facultative symbiont of loggerhead sea turtles PFALLER, JB*; BAEZA, JA; University of Florida, Gainesville; Clemson University, South Carolina jpfaller@ufl.edu

Theory suggests that symbiotic crustaceans should exhibit social monogamy and long-term heterosexual pairing when inhabiting small, scarce hosts in environments where mortality risk away from hosts is high. This prediction was tested in Planes major, a facultative but common symbiont of loggerhead sea turtles (Caretta caretta). In agreement with theory, crabs were found dwelling as heterosexual pairs in the inguinal space of host turtles more frequently than expected by chance alone. Additional observations, however, suggest that male-female pairing in P. major is not necessarily long-term. First, solitary females were commonly found brooding eggs, which suggests some degree of post-copulatory host switching. Second, body size of male and female crabs found in pairs and body size of crabs and host turtles were weakly correlated, which suggests the crabs form short-term associations with their individual hosts and, consequently, with the other crab inhabiting the same host. Third, we found sexual dimorphism in weaponry, which suggests that males compete for and/or defend receptive females via overt aggression. Collectively, these results suggest that P. major is indeed socially monogamous (males and females frequently inhabit host individuals as heterosexual pairs), but monogamy is not long lasting as males (and/or females) switch among host individuals in search of extra-pair copulations. Additional experimental studies are needed to understand the conditions favoring the evolution and adaptive value of short- and long-term monogamy in symbiotic crustaceans and other marine invertebrates.