A skeleton‐less sponge of C aribbean mangroves: invasive or undescribed?

Recent surveys of sponges occurring on Caribbean mangrove roots demonstrated the presence of a skeleton‐less sponge of the genus H alisarca, very similar in its morphology to the temperate H . dujardinii . This study evaluated the possibility that the mangrove sponge was actually H . dujardinii that had been introduced into the Caribbean mangroves. Detailed histology revealed differences between the mangrove sponge and H . dujardinii in cuticle thickness, and in characteristics of the choanocytes, spherulous, and granular cells. Also, phylogenetic reconstruction and genetic distance estimates based on cytochrome oxidase I gene sequences clearly differentiated the mangrove H alisarca sp. from H . dujardinii . Therefore, we rejected the hypothesis of the invasion of H . dujardinii , recognizing instead the mangrove H alisarca sp. as a new species and naming it H . restingaensis sp. nov. Estimated levels of genetic variation in the ribosomal internal transcribed spacers indicated that populations of H . restingaensis sp. nov. are highly differentiated between Venezuela and Panama ( F st =0.71). This level of population differentiation is consistent with the short larval competence period that is common in members of the genus H alisarca .