title: Possible factors responsible for the toxicity of Cochlodinium polykrikoides, a red tide phytoplankton.
abstract: Cochlodinium polykrikoides, a harmful red tide dinoflagellate, is highly toxic to fish, but the toxic mechanism is still unknown. Recent study has suggested that C. polykrikoides generates reactive oxygen species (ROS) such as superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)), and the ROS-mediated ichthyotoxicity has been proposed. In this study, we found that the levels of O(2)(-) and H(2)O(2) detected in C. polykrikoides were trace levels as compared with those of Chattonella marina which is well-known to produce ROS. Furthermore, no significant increase in O(2)(-) generation by C. polykrikoides was observed in the presence of lectins such as concanavalin A (Con A) and wheat germ agglutinin (WGA) or fish mucus prepared from skin and gill of yellowtail, whereas C. marina generated increased level of O(2)(-) responding to these stimuli. Interestingly, the cell-free aqueous extract prepared from C. polykrikoides showed toxic effect on the HeLa cells, but the extract of C. marina had no significant effect. Furthermore, gradual accumulation of polysaccharides in the medium was observed during the growth of C. polykrikoides, and the medium gradually became viscous, but no such changes were observed in the medium of C. marina. These results suggest that multiple factors may be responsible for the toxic mechanism of C. polykrikoides.
authors.affiliation: Japan Society for the Promotion of Science, Water and Soil Environment Division, National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Daekyung
authors.initials: D
authors.lastname: Kim
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Oda
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Daeil
authors.initials: D
authors.lastname: Kim
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Matsuyama
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Honjo
mesh_terms: D000818:Animals; D002452:Cell Count / Q000379:methods; D004141:Dinoflagellida / Q000302:isolation & purification / Q000378:metabolism*; D005399:Fishes / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D010839:Phytoplankton / Q000302:isolation & purification / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species