Trapezia and Tetralia (Decapoda, Brachyura, Xanthidae) as Obligate Ectoparasites of Pocilloporid and Acroporid Corals

Abstract

The occurrence of marine invertebrates in the branches of living and dead corals has long been recognized. Two crab genera, Trapezia and Tetralia, of the family Xanthidae are determined by Garth (1964) as being obligate commensals of the coral families Pocilloporidae and Acroporidae, respectively. Crane (1947) lists species of the genus Trapezia as being found only in pocilloporid corals along the west coast of tropical America. Miyake (1939), in listing the Brachyura of Micronesia, records Trapezia cymodoce as collected from Stylophora, a pocilloporid coral. Garth 's original collecting techniques used at Eniwetok Atoll, Marshall Islands, were refined in his later collecting in July 1959, at which time he segregated each collection of coral by species to avoid mixing coral commensals found therein.