Occurrence and Effects of Barnacle Infestations on Diamondback Terrapins (Malaclemys terrapin)

The occurrence and effects of barnacle infestations on two populations of diamondback terrapins were studied from 1977 to 1979 at the Merritt Island National Wildlife Refuge, Brevard Co., Florida. Three species of barnacles were found on Malaclemys: Balanus eburneus, Chelonibia manati and C. testudinaria. Of 125 turtles examined, 76% were infested by barnacles. Barnacles settled on the carapace of turtles significantly more frequently than on the plastron. Infestation rates differed sharply between the two populations. No differences in fouling rates were found between the sexes. The major effects of barnacles on Malaclemys were interference with nesting activity and shell erosion. In a few cases, such erosion was severe enough to cause fatal injuries to turtles. It is suggested that barnacles infesting turtles be considered as parasites, rather than commensals.