Stoeckeria algicida n. gen., n. sp. (Dinophyceae) from the coastal waters off Southern Korea: morphology and small subunit ribosomal DNA gene sequence.

This paper presents a new description of the morphology of the planktonic dinoflagellate Stoeckeria algicida n. gen., n. sp. and a report of the sequence of the small subunit rDNA (SS rDNA) from cultured cells. The vegetative biflagellated cell, gametes, triflagellated planozygotes, and cyst stages of this heterotrophic species were observed in cultures. The vegetative biflagellated cells are oval, with the cell length being considerably larger than the cell width. The ranges (and mean, n=60) of cell length and width of live biflagellated cells satiated with the raphidophyte Heterosigma akashiwo were 14.4-20.8 microm (16.8) and 10.0-17.4 microm (12.9), respectively, while those of biflagellated cells starved for 3 d (n=60) were 7.3-15.9 microm (11.6) and 2.7-12.2 microm (7.3), respectively. Thin plates of the vegetative biflagellated cells were arranged in a Kofoidian series of Po, cp, X, 4', 2a, 7'', 6c, 6s, 5''', 0 (p), and 2''''. When properly aligned, the sequence of the SS rDNA of the biflagellated cells of S. algicida (GenBank Accession no. AJ841809) was 3% different from that of a dinoflagellate from Shepherd's Crook and 4% different from that of Cryptoperidiniopsoid sp. brodyi, Pfiesteria spp., or Pfiesteria-like species. In a maximum-likelihood-distance phylogenetic tree generated using the SS rDNA sequences, Pfiesteria spp., Pfiesteria-like species, and a dinoflagellate from Shepherd's Crook were closest to S. algicida, but these dinoflagellates were clearly divergent with S. algicida. Based on morphological and genealogical analyses, we suggest that this is a new species in a new genus.