Overview of the biodiversity and distribution of the Class Homoscleromorpha in the Tropical Western Atlantic

Abstract

In this study we revise the current knowledge on the biodiversity and distribution of the Class Homoscleromorpha in the Tropical Western Atlantic (TWA). Twenty-seven species are currently recognized in the TWA, belonging to the generaOscarella(O. nathaliae),Plakortis(P. angulospiculatus, P. dariae, P. edwardsi, P. halichondrioides, P. insularis, P. microrhabdifera, P. myrae, P. petrupaulensis, P. potiguarensis, P. simplex, P. spinalis, P. zyggompha),Plakinastrella(P. globularis, P. microspiculifera, P. onkodes, P. stinapa),Plakina(P. coerulea, P. elisa, P. jamaicensis, P. monolopha, P. tetralopha, P. trilopha, P. versatilis),Corticium(C. diamantense, C. quadripartitum) andTetralophophora(T. mesoamericana). Three of these ‘species’ are cosmopolitan and in fact represent complexes of cryptic species:Plakina monolopha, P. trilophaandPlakortis simplex. All other 24 species reported are TWA endemics. Only four species are found both in the Caribbean and in Brazil:Plakortis angulospiculatus, P. halichondrioides, Plakinastrella microspiculiferaandP. onkodes, but these may also be species complexes. Seven species are Brazilian endemics:Plakina coerulea, Plakinastrella globularis, Plakortis insularis, P. microrhabdifera, P. petrupaulensis, P. potiguarensisandP. spinalis. Thirteen species are restricted to the Tropical North-western Atlantic:Corticium diamantense, C. quadripartitum, Oscarella nathaliae, Plakina elisa, P. jamaicensis, P. tetralopha, P. versatilis, Plakortis dariae, P. edwardsi, P. myrae, P. zyggompha, Plakinastrella stinapaandTetralophophora mesoamericana. The Greater Antilles is the richest ecoregion, with 12 species reported. Only the Guianan ecoregion has no records of Homoscleromorpha. Several undescribed species ofOscarellaandPlakinaare also known from the TWA. We estimate that the biodiversity of Homoscleromorpha in the TWA is at least twice as high than currently known.