First records of the dinoflagellate genus Dicroerisma (Actiniscales, Dinophyceae) in the Mediterranean Sea

About 700 species of dinoflagellates have been reported in the Mediterranean Sea, including ca. 90% of the dinoflagellate genera of the world’s oceans (GÓMEZ, 2003, 2005). Despite the historical tradition of taxonomic studies, some genera remain unreported in the Mediterranean basin. TAylor & CATTEll (1969) described the genus Dicroerisma from Canadian Pacific coastal waters. The type, D. psilonereiella F.J.r. Taylor & S.A. Cattell, was described as a nonphotosynthetic gymnodinioid cell possessing a single, hollow, internal skeletal element, longitudinally orientated and forked in the manner of an inverted y. Dicroerisma psilonereiella was later reported from other cold regions of the northern hemisphere (HArvEy et al., 1997; BérArD-THErriAulT et al., 1999; HornEr et al., 2005; SiMAkovA & konovAlovA, 1995; SErGEEThis study is the first to describe and illustrate the dinoflagellate genus Dicroerisma in the Mediterranean Sea. Twenty individuals ascribed to Dicroerisma psilonereiella were encountered. The highest abundance (12 cells L-1) was recorded in the Balearic Sea at 50 m depth. Other specimens were found in subsurface waters (>75 m depth, with some records at 250 m depth) in the Ionian and Levantine Basin. These findings suggest that Dicroerisma is a widespread genus and its presence has gone unnoticed due to its small size, deep water distribution and misidentification with other gymnodinioid cells