Abstract
The effects of temperature on growth and production of Lipophilic Toxins (LT) by a monoclonal culture of Dinophysis caudata was studied. The cell density of D. caudata increased significantly with increasing temperature, and was the highest under 27, 30, and 32.5 °C. Temperature affected the average specific growth rate (µ) during the exponential growth phase (EG), which increased from 15 °C to 30 °C, and then decreased at 32.5 °C. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) revealed that this strain of D. caudata produced only pectenotoxin-2 (PTX-2) whose concentration increased significantly with incubation period, except at 32.5 °C. It was significantly different between temperatures ≤18 °C, ≥21 °C, and 32.5 °C. The cellular toxin production (CTP, pg·cell−1·day−1) showed variation with growth phase and temperature, except at 32.5 °C. The average net toxin production (Rtox) was not affected by temperature. During EG, the average specific toxin production rate (µtox) increased significantly with increase in temperature, reaching a peak of 0.66 ± 0.01 day−1 at 30 °C, and then decreased. Over the entire growth span, µtox was significantly correlated to µ, and this correlation was most significant at 27 and 30 °C. During EG, µtox was affected by both temperature and growth. This study shows that temperature affects growth and toxin production of this strain of D. caudata during EG. In addition, a positive correlation was found between toxin production and growth.
Highlights
The human seafood-borne intoxication known as diarrheic shellfish poisoning (DSP) was first identified in Japan in the 1970s [1]
The diarrheic shellfish toxins (DST) complex comprised three groups of lipophilic toxins that often co-occur in natural samples of plankton and shellfish, and are detected all together by the conventional mouse bioassay (MBA): the okadaic acid (OA) and its analogues the dinophysistoxins (DTX), the yessotoxins (YTX), and the pectenotoxins (PTX) [2,3]
The present study considers the effect of seven experimental temperatures, covering the natural range of geographical distribution of D. caudata, on the growth and toxin production of a strain isolated from western Japan and maintained in a monoclonal culture
Summary
The human seafood-borne intoxication known as diarrheic shellfish poisoning (DSP) was first identified in Japan in the 1970s [1] It is associated with the consumption of bivalve molluscs contaminated with lipophilic, polyether, diarrheic shellfish toxins (DST) produced by marine microalgae. The genus Dinophysis regroups over a 100 species of pigmented dinoflagellates, some of which have been shown to be mixotrophic [23,24] Among these species of cosmopolitan, polymorphic, and mostly rare marine protists, typically exhibiting low cell densities of 10–102 cells L1 and atypically occurring at 104–105 cells L1 in coastal waters [22,23,25], 12 have been found to produce OA, DTX, and/or PTX, and seven have been associated with DSP events (D. acuminata, D. acuta, D. caudata, D. fortii, D. miles, D. ovum, and D. sacculus) [26]. The present study considers the effect of seven experimental temperatures, covering the natural range of geographical distribution of D. caudata, on the growth and toxin production of a strain isolated from western Japan and maintained in a monoclonal culture
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