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We compiled known occurrence records of seven species of crabs identified in the literature and one documented in this report as having undergone range extensions in southern Africa. Of these eight species, six (Austruca occidentalis , Neosarmatium africanum , Ocypode ceratophthalmus , Portunus segnis , Tubuca urvillei , and Varuna litterata) have extended their ranges either across a major biogeographic boundary that separates the subtropical and warm temperate ecoregions of this coast, or into estuaries that historically lack mangrove forests. For the seventh and eighth species, Charybdis smithii and Scylla serrata , we were unable to find any distributional data that supported poleward range extension. In addition, we contribute the first record of the blue swimming crab, P. segnis , from the temperate south coast of South Africa. This early detection is likely to be part of an ongoing regional trend of tropical-adapted brachyuran crab species extending their ranges into temperate ecoregions. Résumé: Nous avons compilé les données d'occurrence connues de sept espèces de crabes identifiées dans la littérature et une documentée dans ce rapport comme ayant développé des extensions de répartition en Afrique du Sud. Sur ces huit espèces, six (Austruca occidentalis , Neosarmatium africanum , Ocypode ceratophthalmus , Portunus segnis , Tubuca urvillei , et Varuna litterata) ont étendu leur répartition soit à travers une limite biogéographique majeure qui sépare les écorégions subtropicale et tempérée chaude de cette côte, soit dans les estuaires qui historiquement n'ont pas de forêt de mangrove. Pour les septième et huitième espèces, Charybdis smithii et Scylla serrata , nous n'avons pas pu trouver de données de distribution qui supportent une extension vers le pôle. De plus, nous apportons le premier signalement du crabe bleu P. segnis , de la côte tempérée sud de l'Afrique du Sud. Cette première détection s'inscrit probablement dans une tendance régionale en cours des espèces de brachyures adaptées aux tropiques qui étendent leur aire de répartition vers des écorégions tempérées. [ABSTRACT FROM AUTHOR]

East Africa has a reduced mangrove crab species richness when compared to Asian mangroves. To date, only one species of Perisesarma de Man, 1895 has been reported in East Africa, despite more than 30 years of mangrove research in this region. Based on morphology, colour, mtDNA and behaviour, we describe a new species of Perisesarma from Kenya, P. samawati sp. nov. Surprisingly, when comparing molecular data from other species within this genus, P. samawati sp. nov. and the sympatric P. guttatum (A. Milne Edwards, 1869) are not sister species. Some aspects of the ecology of P. guttatum and P. samawati sp. nov. are compared and the differences discussed. Additionally, we compare P. samawati sp. nov. with the ecological literature of a possible sister species P. eumolpe from Malaysian mangroves. Our findings suggest that the new species is an ecologically important species in East African mangroves. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 141, 435–445. [ABSTRACT FROM AUTHOR]

The behavior and ecology of two mangrove crabs, Sesarma meinerti De Man, 1887 and Cardisoma carnifex (Herbst, 1794) were investigated at the beginning of the rainy season (October-November 1988) at Mida Creek, Kenya. Both species occupy upper intertidal levels, above mean high-water neap, and completely overlap in their zonation. Each burrow lasts ca. 3 wk, with no significant difference between the species. Both are more active around dusk and dawn and also follow a similar trend in their foraging activity, but differ in that burrowing is mainly diurnal in C. carnifex and nocturnal in S. meinerti. A hierarchy of food preference, established by offering C. carnifex and S. meinerti leaves of five mangrove species, proved similar for both, with Bruguiera gymnorhiza ranking first and Avicennia marina last, but significant only for C. carnifex. A rough estimate of the amount of litter consumed by these two species and of the soil mixed up by their burrowing activity indicates that they play a role of primary importance in the ecology of East African mangroves. [ABSTRACT FROM AUTHOR]