Intracellular haemolytic agents of Heterocapsa circularisquama exhibit toxic effects on H. circularisquama cells themselves and suppress both cell-mediated haemolytic activity and toxicity to rotifers (Brachionus plicatilis).
A harmful dinoflagellate, Heterocapsa circularisquama, is highly toxic to shellfish and the zooplankton rotifer Brachionus plicatilis. A previous study found that H. circularisquama has both light-dependent and -independent haemolytic agents, which might be responsible for its toxicity. Detailed analysis of the haemolytic activity of H. circularisquama suggested that light-independent haemolytic activity was mediated mainly through intact cells, whereas light-dependent haemolytic activity was mediated by intracellular agents which can be discharged from ruptured cells. Because H. circularisquama showed similar toxicity to rotifers regardless of the light conditions, and because ultrasonic ruptured H. circularisquama cells showed no significant toxicity to rotifers, it was suggested that live cell-mediated light-independent haemolytic activity is a major factor responsible for the observed toxicity to rotifers. Interestingly, the ultrasonic-ruptured cells of H. circularisquama suppressed their own lethal effect on the rotifers. Analysis of samples of the cell contents (supernatant) and cell fragments (precipitate) prepared from the ruptured H. circularisquama cells indicated that the cell contents contain inhibitors for the light-independent cell-mediated haemolytic activity, toxins affecting H. circularisquama cells themselves, as well as light-dependent haemolytic agents. Ethanol extract prepared from H. circularisquama, which is supposed to contain a porphyrin derivative that displays photosensitising haemolytic activity, showed potent toxicity to Chattonella marina, Chattonella antiqua, and Karenia mikimotoi, as well as to H. circularisquama at the concentration range at which no significant toxicity to rotifers was observed. Analysis on a column of Sephadex LH-20 revealed that light-dependent haemolytic activity and inhibitory activity on cell-mediated light-independent haemolytic activity existed in two separate fractions (f-2 and f-3), suggesting that both activities might be derived from common compounds. Our results suggest that the photosensitising haemolytic toxin discharged from ruptured H. circularisquama cells has a relatively broad spectrum of phytoplankton toxicity, and that physical collapse of H. circularisquama cells can lead not only to the disappearance of its own toxicity, but also to mitigation of the effects of other HABs.
Graduate School of Fisheries Science & Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Tomoki
T
Nishiguchi
Jeju Center, Korea Basic Science Institute (KBSI), Smart Building 1F, Jeju Science Park, 2170-2, Ara-dong, Jeju-Si, Jeju Special Self-Governing Province 690-756, Republic of Korea; Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, Republic of Korea.
Kichul
K
Cho
Graduate School of Fisheries Science & Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Masumi
M
Yasutomi
Graduate School of Fisheries Science & Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Mikinori
M
Ueno
Graduate School of Fisheries Science & Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Kenichi
K
Yamaguchi
Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan.
Leila
L
Basti
Department of Applied Aquabiology, National Fisheries University, 2-7-1 Nagata-Honmachi, Shimonoseki, Yamaguchi 759-6595, Japan.
Yasuhiro
Y
Yamasaki
Joint Research Division, Center for Industry, University and Government Cooperation, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan.
Satoshi
S
Takeshita
Jeju Center, Korea Basic Science Institute (KBSI), Smart Building 1F, Jeju Science Park, 2170-2, Ara-dong, Jeju-Si, Jeju Special Self-Governing Province 690-756, Republic of Korea. Electronic address: dkim@kbsi.re.kr.
Daekyung
D
Kim
Graduate School of Fisheries Science & Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan. Electronic address: t-oda@nagasaki-u.ac.jp.
Tatsuya
T
Oda
D000818:Animals; D004141:Dinoflagellida / Q000378:metabolism*; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D053878:Hemolytic Agents / Q000633:toxicity*; D008027:Light; D017319:Photosensitizing Agents / Q000378:metabolism / Q000633:toxicity; D011166:Porphyrins / Q000378:metabolism / Q000633:toxicity; D011817:Rabbits; D012403:Rotifera / Q000187:drug effects*
D053878:Hemolytic Agents; D017319:Photosensitizing Agents; D011166:Porphyrins
Antidote; Brachionus plicatilis; Hemolytic activity; Heterocapsa circularisquama; Mitigation; Porphyrin derivative