Cytological evidence for cryptic speciation in Mediterranean<i>Oscarella</i>species (Porifera, Homoscleromorpha)

Abstract

Three new sponge species without a skeleton, Oscarella viridis, O. microlobata, and O. imperialis, were found in sublittoral caves and on vertical walls along the coast of Provence (western Mediterranean Sea, France). Their morphology, anatomy, and cytology are described and they are compared with the two other valid Mediterranean Oscarella species, O. lobularis and O. tuberculata. Reproductive and internal anatomical characters are uniform in the genus, but details of external morphology and especially cytological characters (mesohylar cells with inclusions) provide good diagnostic features at the species level. Careful observation of morphological and cytological characters is essential for clarifying the systematics of Oscarella and reveals an unexpected biodiversity of this genus in the Mediterranean Sea.