Cave-dwelling calcareous sponges (Porifera: Calcarea) from the Marquesas Islands, French Polynesia

Abstract The Marquesas Islands harbour numerous underwater caves, with different geomorphologies and a rich diversity of invertebrates dominated by sponges. However, although calcareous sponges are known to be abundant in cryptic habitats, only one of the four species reported from Marquesas was found in caves. Hence, our objective was to study the diversity of cave-dwelling calcareous sponges from the Marquesas Islands. Sponges were collected in semi-dark or dark caves, most of them being lava tubes. Through morphological and molecular (ITS and C-LSU) tools, five species were identified, four of them new to science: Borojevia moana sp. nov., Bidderia watremezi sp. nov., Leucascus polynesiensis sp. nov., Leucandra cavernicola sp. nov., and Murrayona phanolepis. In general, sponge assemblages in caves are different from those on adjacent rocky shores. Indeed, in French Polynesia, Leucascus polynesiensis sp. nov. was the sole species found inside and outside caves. We found that M. phanolepis is a cave-dwelling and widespread species, which might represent a cryptic diversity. Besides, aliactine spicules could be a synapomorphy in the subclass Calcaronea. Even though the number of species for the region is still underestimated, it is noticeable that Marquesan caves seem to harbour a unique diversity of calcareous sponges.