NANO alumni publication: The harmful unarmored dinoflagellate Karlodinium in Japan and Philippines, with reference to ultrastructure and micropredation of Karlodinium azanzae sp. nov. (Kareniaceae, Dinophyceae)

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Abstract

Twenty‐six cultures of the harmful marine dinoflagellate Karlodinium , isolated from Japanese and Philippine coastal waters, were examined using LM, SEM and molecular phylogeny inferred from ITS and LSU rDNA. Seven Karlodinium species (6 from Japan and 4 from Philippines), K. australe , K. ballantinum , K. decipiens , K. gentienii , K. veneficum , K. zhouanum , and a novel species Karlodinium azanzae sp. nov., were identified based on their morphology and phylogenetic positions. Karlodinium azanzae from Manila Bay, Philippines was further characterized by TEM, HPLC (chloroplast pigment) and bioassay on brine shrimp and other marine zooplankton. Cells of K. azanzae were the largest (mean 25.3 µm long) in Karlodinium , possessed numerous tiny reflective particles, starch grains and lipid granules, and usually swam at the bottom of the culture vessel. The straight apical structure complex and a ventral pore were common to the genus. The longitudinally elongated nucleus was located at the center, and the yellowish chloroplasts contained an embedded pyrenoid and carotenoid pigments typical of the genus (i.e., fucoxanthin as major carotenoid with its derivatives). TEM revealed a part of the flagellar apparatus, of which the long striated ventral connective is the first report in the Kareniaceae. Phylogenetic trees showed closest affinity of K. azanzae with K. australe and K. armiger. The new species could be differentiated from related species by cell size, position of the nucleus, and characteristic swimming behavior. Lethality of K. azanzae to large zooplankton and micropredation using a developed peduncle were also observed.

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