STUDIES ON DOMECIA ACANTHOPHORA, A COMMENSAL CRAB FROM PUERTO RICO, WITH PARTICULAR REFERENCE TO MODIFICATIONS OF THE CORAL HOST AND FEEDING HABITS WENDELL K. PATTON Ohio U'cslcyan University, Dclait'arc, Ohio 43015 In the summer of 1965, a survey was made of the fauna of living portions of Acropora colonies at La Parguera, on the south coast of Puerto Rico. Collections and underwater observations were made in shallow depths (0-10 feet) at the west end of Enrique Reef. This region has good coral growth but less wave action than the southern, seaward face of the reef (Almy and Carrion-Torres, 1963). Contrary to my expectations, the xanthid crab Domecia acanthophora (Desbonne and Schramm ) was the only commensal found. Studies were made on the biology of this animal and on its relationship with the host coral. I am grateful to Dr. P. W. Glynn, Acting Director of the Institute of Marine Biology of the University of Puerto Rico at Mayagiiez for reading portions of the manuscript and for the assistance which he and the staff of the Institute offered during my stay in Puerto Rico. Dr. John Garth, of the Allan Hancock Founda-tion, kindly donated specimens of Doinccia hispida from the Galapagos Islands. METHODS The coral to be collected was covered as completely as possible with one or more cloth bags while still in place, then broken off and returned to the laboratory for study. Placing the coral inside bags was awkward but necessary since many of the crabs would have escaped if the coral had simply been lifted from the water. At the laboratory dock, the pieces of coral were weighed and carefully examined while the cloth bags were rinsed in a bucket of water which was poured through a fine mesh screen. The crabs found on each colony were collected and measured. In addition, living crabs were studied both in nature and in the laboratory. OBSERVATIONS AND CONCLUSIONS Doinccia acanthophora is a small crab with a mottled brown and cream carapace. Of 180 specimens examined, 162 were above 5.0 mm. in carapace breadth and easily identifiable as to sex, 58 being males and 104 females. The largest male had a carapace breadth of 15.0 mm. while the mean for males was 8.2 mm. For females the comparable figures were 14.0 mm. and 8.4 mm. The smallest ovigerotis female had a carapace breadth of 5.6 mm. 56
BioStor
