THE SPONGIVOROUS DIET OF BATHYCHITON BIONDII  DELL’ANGELO & PALAZZI, 1988 WITH COMMENTS ON THE DIET OF MEDITERRANEAN DEEP SEA CHITONS

During CNR cruise LM99 of r/v Urania, a specimen of the deep-sea polyplacophoran Bathychiton biondii Dell'Angelo & Palazzi, 1988 has been found alive on the surface of a hardground slab dredged from the S.Lucia bank, southern Ligurian sea, at a water depth of 303-180 m. This finding allowed to investigate the trophic habits of one the rarest Mediterranean chitons. In fact, the  specimen was still closely associated with the sponge Hamacantha johnsoni (Bwk) suggesting its potential spongivory. In order to test this hypothesis, we have examined stomach, gut and fecal pellet contents of this specimen as well as those of another rare Mediterranean species (Ischnochiton dolii Van Belle & Dell'Angelo, 1998) by dissecting a specimen living-collected inside a fragment of an amphora at 480m off the Latium coast. The results of our investigation suggest that the diet of both species is mostly based upon sponges. In particular, I. dolii cannot be considered monophagous, since spiculae belonging to different sponge orders were isolated, while for B. biondii there are no conclusive data yet. Spongivory was previously reported in literature only for two Atlantic deep sea chiton species: Hanleya hanleyi (Bean, 1844) and the closely related species H. nagelfar (Lovén, 1846).

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