CYTOLOGICAL EVIDENCE FOR CRYPTIC SPECIATION IN MEDITERRANEAN OSCARELLA SPECIES (PORIFERA, HOMOSCLEROMORPHA)

Three new sponge species without a skeleton, Oscarella viridis, O. mic rolobata, and O. imperialis, were found in sublittoral caves and on ve rtical walls along the coast of Provence (western Mediterranean Sea, F rance). 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 anatomica l characters are uniform in the genus, but details of external morphol ogy and especially cytological characters (mesohylar cells with inclus ions) provide good diagnostic features at the species level. Careful o bservation of morphological and cytological characters is essential fo r clarifying the systematics of Oscarella and reveals an unexpected bi odiversity of this genus in the Mediterranean Sea.