MORPHOLOGICAL AND MOLECULAR EVIDENCE FOR A NEW ENDEMIC FRESH-WATER CRAB, SESARMA-AYATUM SP. N., (GRAPSIDAE, SESARMINAE) FROM EASTERN JAMAICA

Recent morphological studies have shown that the Jamaican mountain str eam crab. Sesarma bidentatum Benedict, 1892 (Sensu Abele 1992), consis ts of several allopatric forms. Three new species have been described from western Jamaica (summarized in Reimer ct al. 1998) restricting th e range of S. bidentatum to central and eastern Jamaica. In this study we used morphology and genetic markers to further distinguish crab po pulations from different East Jamaican river systems. Morphological ch aracters such as the shape of male gonopods, front, chelar carpus, and walking legs, as well as mtDNA sequence (16S rRNA gene) comparisons w ere consistent in the separation of populations of S. bidentatum into two distinct groups. A new species, Sesarma ayatum sp. n., is describe d with a distribution from easternmost Jamaica to the eastern Blue Mou ntains. (C) 1998 The Norwegian Academy of Science and Letters.