The Harmful Unarmored Dinoflagellate Karlodinium in Japan and Philippines, with Reference to Ultrastructure and Micropredation of Karlodinium azanzae sp. nov. (Kareniaceae, Dinophyceae)¹

Abstract

In all, 26 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 (six from Japan and four 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 was also observed.

Fish Kills Related to Harmful Algal Bloom Events in Southeast Asia

“…Fish and Artemia bioassay evaluated and confirmed the presence of highly potent ichthyotoxic compounds in K. veneficum (e.g., [19]). Several studies also demonstrated the stronger micropredation capability of Karlodinium species, e.g., K. armiger, K. australe, K. azanzae and K. veneficum [26][27][28][29]. The presence of polysaccharide compounds or reactive oxygen species (ROS) has been confirmed in some harmful algae.…”

“…The unarmored dinoflagellates in the Kareniaceae, or Brachidiniaceae, have been reported from Southeast Asia [22,27,42]. Karenia mikimotoi, one of the most harmful bloom species in the world, has been recorded from Malaysia, Philippines and Singapore [4,[42][43][44].…”

Review of Harmful Algal Blooms (HABs) Causing Marine Fish Kills: Toxicity and Mitigation

“…The species K. armiger generates karmitoxin, a powerful nanomolar cytotoxin with an -NH 2 (amino) group, which is distinct from K. veneficum and K. conicum and was the primary contributor to fish fatalities from K. armiger [101,102]. None of these mixoplankton species, K. veneficum [103,104], K. armiger [105], and K. azanzae [106], have been adequately studied in terms of phagotrophy. Although dangerous dinoflagellates and haptophytes frequently exhibit phagotrophy, its relevance with respect to HABs is not yet fully understood [98,107].…”

“…De Salas et al [111] initially described K. australe, another species of Karlodinium; however, it was not until 2014 that this species was linked to fish death [112]. K. australe has been witnessed in the coastal waters of southeast Asian nations stretching along Malaysia, Singapore, Philippines to the East China Sea, Japan, and Australia [106,113,114]. This species bloomed in the West Johor Strait in February 2014, killing a significant number of fish in the wild and in cages [112].…”

Morphological variation and phylogeny ofKarenia selliformis(Gymnodiniales, Dinophyceae) in an intensive cold-water algal bloom in eastern Hokkaido, Japan in September–November 2021

“…Among the genera of this family, Asterodinium Sournia, Brachidinium Sournia, Gertia K. Takahashi et Iwataki, Karenia G.Hansen et Moestrup, Karlodinium Larsen, Shimiella Ok, Jeong, Lee et Noh, and Takayama de Salas, Bolch et Hallegraeff, species in Karenia, Karlodinium and Takayama have been reported as harmful algal bloom (HAB) causative species (Daugbjerg et al, 2000;de Salas et al, 2003;Benico et al, 2019;Takahashi et al, 2019;Ok et al, 2021). In the Northwest Pacific, fisheries damage has been reported with kareniacean blooms of Karenia mikimotoi (Miyake et Kominami ex Oda) G. Hansen Takayama acrotrocha Larsen, both in the Southeast and East Asia (Yang et al, 2000(Yang et al, , 2001Lim et al, 2014;Tang et al, 2014;Yamaguchi et al, 2016;Benico et al, 2020). In Japanese coastal waters, Kr.…”