ZARDUS, J.D.*; HADFIELD, M.G.; University of Hawaii, Kewalo Marine Lab: Larval development, breeding system and host selection in a turtle barnacle: intriguing aspects of a commensal life-history

Turtle barnacles are obligate commensals of sea turtles and comprise several genera in the balanomorph family Coronulidae. They colonize all seven species of marine turtles worldwide, but host specificity varies by species as does attachment mode; some cement to turtle scutes and scales, others grip the skin and one bores into the shell. How their life-histories facilitate the colonization of turtles and how their population dynamics are influenced by host behavior are intriguing questions. Heretofore, complete life cycles have not been reported for any turtle barnacle nor have factors promoting their association with turtles been examined. To begin bridging these fundamental gaps in understanding, we documented larval development and tested settlement selectivity in Chelonibia testudinaria,a scute-cementing species. We reared it from egg to settlement and metamorphosis, confirming that it follows the typical barnacle pattern of six naupliar stages followed by a non-feeding cyprid. We also found complemental males (apparently dwarf protandric individuals) attached to the opercular valves and settled in pits in the crevices between wall plates of large hermaphrodites. Using larvae from this species, we tested selectivity in laboratory experiments by offering sections of scute from several species of sea turtles along with artificial materials as a settlement substratum. A preference for green turtle over hawksbill was found in preliminary trials. Tests with other species are currently in progress. Differential settlement of barnacles by host species may influence population connectivity and isolation. Preliminary findings on genetic population structure are presented, and the possibility of using barnacles as turtle-tracking devices is discussed.