Effect of temperature on production of okadaic acid, dinophysistoxin-1, and pectenotoxin-2 by Dinophysis acuminata in culture experiments

摘要

ABSTRACT: We cultivated Dinophysis acuminata, a mixotrophic dinoflagellate causing diarrhetic shellfish poisoning worldwide, at different temperatures by providing a mixotrophic ciliate Myrionecta rubra as a food source. We examined the effects of temperature on growth rates and monitored production of the toxins okadaic acid (OA), dinophysistoxin-1 (DTX1), and pectenotoxin-2 (PTX2) using liquid chromatography-tandem mass spectrometry. Cell densities of D. acuminata increased at temperatures of 10, 14, 18, and 22°C, and the mean specific growth rates during the exponential growth phase were higher at higher temperatures (0.14 to 0.28 d–1). The concentration of all toxins increased as cell densities increased. The mean cellular PTX2 content during the exponential growth phase was greater at lower temperatures, but clear differences in the other toxin concentrations in relation to temperature were not observed. The cellular content of OA and DTX1 significantly increased during the exponential growth phase at all temperatures except at 10°C for OA, whereas that of PTX2 did not significantly increase at temperatures greater than 10°C. Cellular toxin production rates temporarily increased at or just before the end of the exponential growth phase at 14, 18, and 22°C, and the mean rates for OA production over the entire incubation period were higher at higher temperatures. Our results indicate that increasing temperature generally stimulates toxin production in D. acuminata populations due to an increase in cell density, but cellular content and production rates of OA and PTX2 in response to temperature differ and are influenced by growth phase.