The genus Acanthodendrilla in the Mediterranean Sea with description of a new species

Three specimens of a keratose sponge not ascribable to any known Mediterranean genus were collected by trawling off the continental shelf of the Blanes littoral (NE Spain, western Mediterranean). The sponge is foliose, erect, attached to the substratum by one or several short stalks. The stalks skeleton is formed by ascendant fascicled fibres, which repeatedly divide, anastomose, and reticulate in the foliose part, to form a dendro-reticulate network. The surface is conulose with long conules, up to 5 mm apart. Fibres have distinct pith filled with noticeable amounts of foreign debris, and a multi-stratified bark. The skeleton features do not match those of any genus known from the Mediterranean Sea but are similar to a new genus recently described from the Indo-Pacific: Acanthodendrilla Bergquist, which was represented up to now by the species A. australis. The Mediterranean species, here described as Acanthodendrilla levii n. sp., differs from A. australis in its dendro-reticulate skeleton (instead of that totally reticulated in the Pacific species), the way the sponge attaches to the substratum by means of one or several short stalks (which are absent from A. australis), and its foliose thin growth habit (instead of that massive and thicker in A. australis). The finding of a second species confirms the validity of the genus Acanthodendrilla. This is the first record of the genus outside the type locality, and the first time that a representative of the family Dictyodendrillidae has been reported in the Mediterranean Sea.