Phycologia (2004) Volume 43 (4), 416-421 Published 30 July 2004 RESEARCH NOTE Observations on Ceratoperidinium (Dinophyceae) FERNANDO GO ´ MEZ 1* ,YUKIO NAGAHAMA 1 ,YASUWO FUKUYO 2 AND KEN FURUYA 1 1 Department of Aquatic Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan 2 Asian Natural Science Environmental Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan F. GO ´ MEZ,Y.NAGAHAMA,Y.FUKUYO AND K. FURUYA. 2004. Observations on Ceratoperidinium (Dinophyceae). Phycologia 43: 416-421. Until now, the rare dinoflagellate genus Ceratoperidinium Margalef has been recorded only from the Mediterranean Sea. For the first time, photomicrographs (bright field, Nomarski and epifluorescence) are reported from Lugol-fixed samples collected from the Sulu and Celebes Seas and the western Equatorial Pacific Ocean. The specimens showed high variability in the relative size of the flexible extensions. Several specimens corresponded to the type species, Ceratoperidinium yeye, and lacked the apical extension. Other specimens showed an apical extension of variable size that corresponded to the description of C. mediterraneaum. This taxon is considered to be a morphological variety of C. yeye on the basis of the high interspecimen variability in the length of the extensions; specimens intermediate between C. yeye and C. mediterra- neaum occur where both forms coexist. The ventral view is proposed (confirmed by 4,6-diamidino-2-phenylindole staining) to be that with the nucleus located in the left side of the cell. Thecal plates were not observed in specimens stained with Fluorescent Brightener 28. Consequently, the placement of this genus in the order Peridiniales on the basis of the initial description from a single cell should be reconsidered. Ceratoperidinium Margalef is a genus of planktonic marine dinoflagellate rarely reported in the literature. Margalef (1969) described the type species Ceratoperidinium yeye Margalef from a single individual collected in coastal waters of the Spanish Mediterranean Sea. Margalef reported a cell body that was pentagonal in outline and compressed dorsoventrally. The cingulum was weakly impressed and a sulcus was not ob- served. The cell surface was rigid and lacked sculpture or relief. No thecal plates were observed. The hypotheca (hy- posoma) was drawn out into two long, slightly curved, rigid, cylindrical appendices with a row of three swellings at their extremities. The tips of the antapical extensions presented a tentacle-like shape. One large pusule, plastids and small drops of lipid occur in the cytoplasm and the nucleus is centrally located. Later, Loeblich (1982, p. 108) and Sournia (1986, p. 96) translated the description by Margalef (1969) to English and French, respectively. The type species was redescribed as C. margalefii by Loe- blich (1980) because of the absence of a Latin diagnosis. As reported by Sournia (1982, p. 153), Loeblich only added the Latin diagnosis, but instead of retaining the name with a new authority, C. yeye Margalef ex Loeblich III, he proposed the new name C. margalefii Loeblich III. The case of C. yeye is comparable to that of taxa such as Petalodinium porcelio J. Cachon & M. Cachon, in which the original publication of the type species lacked the Latin diagnosis; under the Inter- national Code of Botanical Nomenclature (Greuter et al. 2000; article 45.5 ex. 5), the name should retain its original author- ship and date. * Corresponding author (fernando.gomez@fitoplancton.com). After the initial record by Margalef (1969), Abboud-Abi Saab (1989) reported one specimen of C. yeye from Lebanese coastal waters. She further reported a new species, C. medi- terraneum Abboud-Abi Saab (Abboud-Abi Saab 1989), that differs from the type species by the presence of a rounded tubular apical (capitate) process. The description of C. medi- terraneum lacked a Latin diagnosis, line drawings and good- quality illustrations. This almost inaccessible publication goes unnoticed in or omitted from later literature. Vela ´squez (1997) reported C. yeye in the Gulf of Lions (NW Mediterranean Sea) and more recently Go ´mez & Ab- boud-Abi Saab (2003) reported new records of C. yeye from the Albora ´n and Balearic Seas. These authors also reported a Ceratoperidinium sp. with a distinctive curved apical process more elongate than that in C. mediterraneum (Go ´mez & Ab- boud-Abi Saab 2003). There are no other records, either for the Mediterranean Sea (Go ´mez 2003) or for the rest of the world, to the best of our knowledge. Ceratoperidinium has been placed in the family Ceratoper- idiniaceae Margalef (Loeblich 1982) or incertae sedis (Sour- nia 1986), both in the order Peridiniales Haeckel, and later tentatively as an unarmoured taxon of the order Ptychodis- cales Fensome, Taylor, Norris, Sarjeant, Wharton & Williams (Fensome et al. 1993). This study presents photographic records of the genus for the first time. We tried to elucidate the presence of cellulose thecal plates by using the Fluorescent Brightener staining technique. The position and the shape of the nucleus were studied by using a DNA fluorochrome. The orientation of the cell is proposed for the first time. The morphological vari- ability in the relative size of the extensions is emphasized. Cambiado con la DEMO VERSION de CAD-KAS PDF-Editor (http:/ / www.cadkas.com).