SHALLOW-WATER AND TERRESTRIAL BRACHYURAN CRABS OF ROATAN AND THE SWAN ISLANDS, HONDURAS ,„„.„,> CRUSTACEA LIP"' DONALD E. KEITH JJJM^HSONLAHJ '1 KEITH, DONALD E. 1985 12 30. Shallow-water and terrestrial brachyuran crabs of Roatan ant SAR5IA the Swan Islands, Honduras. - Sarsia 70:251-278. Bergen. ISSN 0036-4827. There are relatively few published accounts of Brachuyra from the northwestern Caribbean and none dealing specifically with the Bay Islands and Swan Islands off mainland Honduras. Brachyura were collected from shallow-water and terrestrial habitats at the Swan Islands from April 1973 through June 1976 and at Roatan and other Bay Islands from May 1975 through March 1979. Sixty-seven species are reported including 32 from the Swan Islands and 50 from Roatan. Of these, 21 species were not previously reported from northwestern Caribbean waters. One new species of Potamocarcinus was discovered in a freshwater stream at Port Royal, Roatan. Species diversity was greater at Roatan resulting primarily from the much greater diversity of habitats. Donald E. Keith, Department of Biological Sciences, Tarleton State University, Tarleton Station, Stephenville, Texas 76402, U.S.A. Swan. There is no source of freshwater. One INTRODUCTION brackish-water pool is located near Buffalo Point. There are few published accounts of Brachyura from Drinking-water on the Islands is obtained from the western Caribbean and none dealing specifically cisterns constructed by the US. Weather Service. with the Bay Islands or Swan Islands, Honduras. There are no mangroves or mud flats as found on the Major taxonomic publications on west Indian Brach- Bay Islands. The low habitat diversity results in a yura include papers by CHACE & HOBBS (1969) and low diversity of crab species as compared to the Bay RATHBUN (1933). Other broad resources of major Islands. Principal habitat types at the Swan Islands taxonomic significance include four monographs by include coral reefs, Thalassia flats with loose coral RATHBUN (1918, 1925, 1930, 1937) on crabs of rubble, rocky shores, sand beaches, and wooded America and papers by WILLIAMS (1965), GUINOT terrestrial areas. Of the 32 species collected from the (1970), and GARTH (1978). POWERS' (1977) catalog Swan Islands, none was limited to the islands and and bibliography of crabs of the Gulf of Mexico also most ranged throughout the Caribbean. contains Caribbean species. Taxonomic nomencla- The Bay Islands include 65 cays and 8 islands of ture in this study follows primarily that of RATHBUN which Roatan is the largest. Besides Roatan, Saint except where noted. GUINOT (1970) made major Helene, Morat, and Barbaret were also visited. revisions of genera in the family Xanthidae. These Roatan, however, was most extensively collected revisions have been included, and RATHBUN'S older during the study. This island is approximately 30 km nomenclature also cited. GARTH (1978) used Gui- long and has 4 km maximum width. It is the not's revised names as subgenera of the older emergent crest of a narrow ridge which runs along genera. the south side of the Bartlett Trough. An account of The Swan Islands and Bay Islands are located in the geology of the island is given by MCBIRNEY & the northwestern Caribbean off the coast of BASS (1969). Geographical information may be mainland Honduras. The Swan Islands are situated found in DAVIDSON (1974). approximately 160 km northeast of the Honduran Unlike the Swan Islands, Roatan has an extreme coast and the Bay Islands about 50 km north of the diversity of habitats including coral reefs, Thalassia mainland (Fig. 1). flats, cobble and sand beaches, rocky shores, man- Three islands oonstitute the Swan Islands chain: grove swamps, mud flats, estuarine bays, freshwater Great Swan, Little Swan, and Booby Cay. Fringing streams, and wooded terrestrial areas. The increased reefs are developed around the perimeter of the habitat diversity results in an increased crab diversi- islands with the most extensive reef growth occurr- ty. Fifty crab species were identified from Roatan. ing along the northern shores. This paper provides a convenient means for Habitat diversity at the Swan Islands is consider- recognizing most of the Bay Islands and Swan ably less than at the Bay Islands. Maximum eleva- Islands species and includes information important tion on Great Swan is only 14 m and 20 m on Little to the geographic distribution of many Caribbean 251 Dromia erythropus (GEORGE EDWARDS, 1771) Fig. 2A. Distinguishing features. Carapace pilose, wi- der than long with posterior lateral margins converg- ing. Front small and tridentate. Four prominent anterior lateral teeth. Range. From Bermuda and the Bahamas, throughout the Gulf of Mexico and Caribbean to Sao Paulo, Brazil. Habitat. Hard substrates including corals, shells, and rocks. Reported by FEEDER (1973) to be most common at depths of less than 46 m, but known to 364 m from some areas. Remarks. The dorsal surface of the carapace is characteristically covered with sponges or compound ascidians. A single specimen was collected at Fort Cay near the water's edge where it presumably was washed in from the nearby reef. Dromidia antillensis STIMPSON, 1858 Fig 2B. Distinguishing features. Carapace pubescent, species. Distinguishing features are given for each longer than braod with posterior lateral margins species as an aid for recognizing differences between subparallel. Frontal region longitudinally grooved related crabs and are not intended to be species along middle; front strongly deflexed and 5-toothed descriptions. including supraorbital teeth. Lateral margins of carapace 4-toothed and deflected toward corner of MATERIAL AND METHODS buccal areas. Brachyuran collections were made from terrestrial and Range. From Bermuda, North Carolina, Bahamas shallow-water habitats at the Swan Islands during April and Gulf of Mexico, throughout the Caribbean to 1973, July 1974. January 1975 and June 1976. Crabs were Espirito Santo, Brazil. collected by hand during the day. Night collections were Habitat. Reported from hard bottoms such as also made intertidally and in various terrestrial habitats using lights and nets. Collections from coral reef habitats rock, shells, and coral at depths from shore to 331 m. were made with the aid of SCUBA equipment. Some coral Collected at Roatan in shallow water from Thalassia heads were returned to the lab and pulverized to obtain flats. associated crab species. Shallow-water sediments were Remarks. The dorsal surface is commonly covered screened using a No. 60 standard sieve and the undersur- faces of coral rubble were carefully examined for crabs. by a sponge or compound ascidian. Similar techniques were used to collect brachyurans at Roatan and other Honduran Bay islands with the addition of dredging. Extensive collections were made along the Subsection Oxystomata southern shores of Roatan during March 1979. Less Family Calappidae extensive collections were made at Saint Helene and Barbaret. Collections of brachyurans made by Dr. J. C. Calappa angusta A. MILNE EDWARDS, 1880 Britton, Texas Christian University, during May 1975, May Fig. 2C. 1976, and March 1977 were also examined. May 1975 collections included some crabs taken by dredging in Distinguishing features. Carapace slightly wid- approximately 35 m of water off Roatan. er than long with anterolateral margins finely Drawings of crabs included in this study were made by granulate, with somewhat larger granules at inter- tracing projected transparencies of each species. Fine vals; front bilobed. Tooth at posterolateral angle of details were added by microscopic examination. carapace is largest followed anteriorly by four smaller teeth diminishing in size, and posteriorly by SYSTEMATIC ACCOUNT one small and one or two very minute teeth. Orbit Section Brachyura completely separated from antennular cavity. Cheli- peds with upper margin of palm bearing six to eight Subsection Dromiacea teeth and lateral margins with coarse granules Family Dromiidae interspersed with tubercles. 252 Range. North Carolina, Florida, Gulf of Mexico, and sand bottoms from depths from 13 to 274 m. Yucatan to Grenada and Barbados. Specimens were collected at Roatan by dredging Habitat. Reported from coral, broken shell, gravel over Thalassia flats. 253 Calappa gallus (HERBST, 1803) Habitat. Reported from coral, sand, gravel and Fig. 2D. shell bottoms from depths of 10 to 329 m. At Roatar Distinguishing features.Carapace width slight- this species was collected from dredges over a ly exceeds length with anterior two-thirds covered sand-flat area "at 10 m. with tubercles; posterior one-third bears short gra- Iliacantha sparsa STIMPSON, 1871 nulated ridges. A deep sulcus occurs between the Fig. 3A. gastric and hepatic regions. Longitudinal furrows Distinguishing features. Carapace globular, separate the cardiac and branchial regions. Postero- longer than broad with three spines at posterior end lateral expansions well developed with six teeth, which are widely separated and divergent. Median three anterior and two posterior to posterolateral spine longest and all have upturned tips. Spine also tooth. Prominent rostrum with four subequal blunt present on subhepatic margin. Chelipeds with slen- teeth. der palms. Fingers and palm subequal in length. Range. From Bermuda and Florida Keys, Range. Northwest of Tortugas, Puerto Rico, Bar- throughout the Caribbean to Bahia, Brazil. GARTH bados to Bahia, Brazil. Roatan collections extend (1978) reports this species to occur also in the the distribution to the