STUDIES ON DOMECIA ACANTHOPHORA, A COMMENSAL CRAB FROM PUERTO RICO, WITH PARTICULAR REFERENCE TO MODIFICATIONS OF THE CORAL HOST AND FEEDING HABITS

Abstract

1. The xanthid crab Domecia acanthophora was collected from three species of the coral Acropora at Enrique Reef, La Parguera, Puerto Rico. 2. The commensal was most commonly found on the flattened coral sheets of Acropora palmata. Here the majority of crabs inhabit various types of structural deformation of the coral which are called resting places. These are believed to be formed by the growth of the coral around and to some extent away from a resting crab. 3. Although undisturbed crabs remain quite motionless, ones which are disturbed are capable of rapid movement over the colony. There is at least some movement of crabs around the reef as vacated resting places will be re-occupied by new crabs. 4. The mouthparts of D. acanthophora differ from those found in typical crabs. In particular, the mandible is weakly calcified and the second maxilliped possesses rows of peculiar paddle-tipped spines on the distal margin of the dactyl. The most likely food for the animal seems to be organic detritus which it separates from the surrounding water. 5. The genus Acropora harbors numerous commensal decapods in the Indo-Pacific but apparently only one in the Caribbean.