First record of Pseudadenoides kofoidii, a marine sand-dwelling dinoflagellate, from Geoje Island, Korea: morphology, phylogeny, and growth and fatty acid content under different temperature conditions

다국어 초록 (Multilingual Abstract)

To clarify an unidentified marine sand-dwelling dinoflagellate isolated from samples collected at a sandy beachof Geoje Island, Korea, its morphology and molecular phylogeny based on the small and partial large subunit rRNAgene sequences were examined. In addition, growth responses and fatty acid content of the isolate under differenttemperature conditions were investigated to assess its physiological traits and aquaculture potential. Cells were26.3–41.5 μm long (34.8 ± 3.6 μm) and 19.8–40.8 μm deep (28.9 ± 4.8 μm), and a nucleus located in the dorsal half of thecell and pyrenoid surrounded by a starch sheath were observed. Scanning electron microscope observations revealedthat the cells were characterized by a lack of precingular plates, scattered thecal pores, a single flagellar pore and ashallow anterior cingulum. One or two pores were present on the plate 3p, and one pore was consistently observedon plate 4p. The phylogenetic analyses revealed that the Korean isolate can be identified as Pseudadenoides kofoidiithat has not previously been described in Korean coastal area. In the growth experiments, the isolate appeared toprefer moderate temperatures (15 and 20°C) rather than higher temperature (25°C). Although this species exhibitedtemperature-dependent variation in docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) production, P.
kofoidii maintained remarkably high levels of DHA and EPA in its fatty acid composition (>42% of total fatty acids),highlighting its potential as a promising marine source of fatty acids for aquaculture applications.