Cave-dwelling Homoscleromorpha (Porifera) from Cape Verde archipelago (Northeast Atlantic): one new genus of aspiculate Plakinidae and five new species

Abstract

Significant efforts have been made to describe the diversity of the sponge class Homoscleromorpha across various oceanic regions, yet the Tropical Eastern Atlantic remains largely unexplored. The insular nature and volcanic origin of the Cape Verde archipelago favour the presence of numerous submarine caves, which are recognized as favourite habitats for Homoscleromorpha. Prior to this study, three species had previously been reported from shallow-water habitats of Cape Verde: Plakina monolopha, Plakortis simplex, and Oscarella lobularis, and all three species had long been considered cosmopolitan. Our exploration of submarine caves has led to the discovery of four new species and one new genus, belonging to the Families Oscarellidae and Plakinidae: Oscarella antea sp. nov., Aspiculina malanoba gen. nov., sp. nov., Plakinastrella fauvelotae sp. nov., and Plakinastrella freitasi sp. nov. We have also examined the two Plakinidae reported in past studies, which in fact correspond to a fifth new species, here named Plakinastrella cachupa sp. nov. These descriptions have been conducted using an integrative approach, combining molecular investigation with accurate morphological analyses. Among the new taxa, two skeleton-less sponges could be described only after histological and cytological investigations, underscoring the need to generalize this type of approach for all Homoscleromorpha. Additionally, for three new Plakinastrella, we have used, for the first time, a mathematical method to analyse spicule size distributions in different classes. We believe that only detailed descriptions of phenotypes such as these can help to reveal the true diversity of Homoscleromorpha and their evolutionary history.