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

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.

Taxonomy of Plakortis and Plakinastrella (Demospongiae: Plakinidae) from oceanic islands off north-eastern Brazil, with description of three new species

Three species of Plakortis and one of Plakinastrella (Demospongiae: Homosclerophorida) collected mostly at oceanic islands off north-eastern Brazil (Atol das Rocas, Fernando de Noronha and São Pedro e São Paulo Archipelago) are described, three of which are new to science: Plakortis angulospiculatus, P. insularis sp. nov., P. microrhabdifera sp. nov, and Plakinastrella microspiculifera sp. nov. External morphological characters such as colour, oscules, and consistency are sufficient to discriminate all the four species in the field, except Plakortis angulospiculatus from P. microrhabdifera. Internal features such as skeletal arrangement, shape and size of diods, and presence of microrhabds and calthrops are also important taxonomic characters for western Atlantic Plakortis and Plakinastrella. We consider as valid only five species of Plakortis in the western Atlantic: the three species described here plus P. halichondrioides and P. zyggompha. All these species except P. zyggompha have been recorded from Brazil. Plakinastrella has now two species in the western Atlantic, P. onkodes and P. microspiculifera sp. nov. The generic distinction between Plakortis and Plakinastrella is tenuous, based only on the presence of spicule size-classes and of deformed vs normal calthrops, and both genera need detailed revision.