First report of the epiphytic dinoflagellate Gambierdiscus caribaeus in the temperate waters off Jeju Island, Korea: morphology and molecular characterization.

Gambierdiscus spp. are epiphytic, benthic dinoflagellates. Some species have been shown to be toxic and cause ciguatera fish poisoning. We report, for the first time, the occurrence of Gambierdiscus caribaeus isolated from the waters off Jeju Island in Korea. Its morphology was similar to that of the original Belize strains of G. caribaeus. Gambierdiscus caribaeus has been reported in the tropical and subtropical waters of the Pacific, Gulf of Mexico, Caribbean Sea, and Floridian coast. Our report extends its range to the North Pacific Ocean. The plates of the Korean strain were arranged in a Kofoidian series of Po, 3', 7'', 6c, 6s, 5''', 1p, and 2'''', morphologically closer to other strains of G. caribaeus than to G. carpenteri. When properly aligned, its small subunit (SSU) rDNA was 0.5% different from those of Gambierdiscus sp. C-1, a strain that was isolated from the waters off eastern Japan, but was 2.4-4.0% different from those of the NOAA strains of G. caribaeus and 3.1-3.4% different from those of the NOAA strains of G. carpenteri. Additionally, the D1-D3 large subunit (LSU) rDNA sequence of the Korean strain of G. caribaeus was 4.7-5.3% different from those of the NOAA strains of G. caribaeus and 7.1-7.5% different from those of all reported G. carpenteri strains, including the NOAA strains. In phylogenetic trees based on SSU and LSU rDNA sequences, our Korean strain was basal to the clade consisting of the NOAA strains of G. caribaeus, which in turn was sister clade to all reported G. carpenteri strains.

Feeding by the Pfiesteria-like heterotrophic dinoflagellate Luciella masanensis.

To explore the feeding ecology of the Pfiesteria-like dinoflagellate (PLD) Luciella masanensis (GenBank Accession no. AM050344, previously Lucy), we investigated the feeding behavior and the kinds of prey species that L. masanensis fed on and determined its growth and ingestion rates of L. masanensis when it fed on the dinoflagellate Amphidinium carterae and an unidentified cryptophyte species (equivalent spherical diam., ESD=5.6 microm), which were the dominant phototrophic species when L. masanensis and similar small heterotrophic dinoflagellates were abundant in Masan Bay, Korea in 2005. Additionally, these parameters were also measured for L. masanensis fed on blood cells of the perch Lateolabrax japonicus and the raphidophyte Heterosigma akashiwo in the laboratory. Luciella masanensis fed on prey cells by using a peduncle after anchoring the prey with tow filament, and was able to feed on diverse prey such as cryptophytes, raphidophytes, diatoms, mixotrophic dinoflagellates, and the blood cells of fish and humans. Among the prey species tested in the present study, perch blood cells were observed to be the optimal prey for L. masanensis. Specific growth rates of L. masanensis feeding on perch blood cells, A. carterae, H. akashiwo, and the cryptophyte, either increased continuously or became saturated with increasing the mean prey concentration. The maximum specific growth rate of L. masanensis feeding on perch blood cells (1.46/day) was much greater than that of A. carterae (0.59/day), the cryptophyte (0.24/day), or H. akashiwo (0.20/day). The maximum ingestion rate of L. masanensis on perch blood cells (2.6 ng C/grazer/day) was also much higher than that of A. carterae (0.32 ng C/grazer/day), the cryptophyte (0.44 ng C/grazer/day), or H. akashiwo (0.16 ng C/grazer/day). The kinds of prey species which L. masanensis is able to feed on were the same as those of Pfiesteria piscicida, but very different from those of another PLD Stoeckeria algicida. However, the maximum growth and ingestion rates of L. masanensis on perch blood cells, A. carterae, H. akashiwo, and the cryptophyte were considerably lower than those of P. piscicida. Therefore, these three dinoflagellates may occupy different ecological niches in marine planktonic communities, even though they have a similar size and shape and the same feeding mechanisms.

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.