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<p>In May–July 2023, diarrhetic shellfish toxin (DST) exceeding the regulatory limit was detected in shellfish from Kyoto for the first time, and the dominant toxin was dinophysistoxins-3 (DTX3). The toxic marine dinoflagellate <i>Dinophysis</i>, including <i>D. acuminata</i>, <i>D. caudata</i> and <i>D. fortii</i>, was observed. To identify the potential cause of the DST occurrence, unialgal cultures of the three species were isolated from Miyazu Bay to investigate their growth characteristics and toxin production. Additionally, 36 strains of <i>D. fortii</i> were incubated for a month for toxin analyses. In the growth experiment, <i>D. acuminata</i> showed the highest specific growth rate (<i>µ</i>) of 0.32 ± 0.033/day, followed by <i>D. caudata</i> (0.23 ± 0.067/day) and <i>D. fortii</i> (0.20 ± 0.024/day). Toxins produced were DTX1, okadaic acid (OA) and pectenotoxin-2 (PTX2) in <i>D. acuminata</i> and <i>D. fortii</i>, and only PTX2 in <i>D. caudata</i>. In the stationary phase, DTX1 yield was higher in <i>D. fortii</i> (485.3 ± 150.07&#xa0;ng/mL) compared with <i>D. acuminata</i> (13.8 ± 2.15&#xa0;ng/mL), as was the DTX1/OA ratio (<i>D. fortii</i>: 61–318, <i>D. acuminata</i>: 0.122–0.249). Furthermore, 97% of the 35 <i>D. fortii</i> strains also had a high DTX1 yield (137.1 ± 81.43&#xa0;ng/mL) and a high DTX1/OA ratio (26.2–9602.7). The high DTX1/OA ratio in <i>D. fortii</i> was similar to that observed in the highly toxic population in northern Japan that originated from the subarctic waters of the Sea of Japan and may suggest that <i>D. fortii</i> was the potential causative species of the DST incident in Kyoto.</p>

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Comparative growth characteristics and toxin profiles of three Dinophysis species isolated from the first diarrhetic shellfish toxin (DST) incident reported in Miyazu Bay, Kyoto, western Japan

  • 期刊论文

  • 发表日期：

    2026年5月29日

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  • Wai Mun Lum,
  • Hajime Uchida,
  • Yuki Funakoshi,
  • Akira Miyazono,
  • Sirje Sildever,
  • Ryoji Matsushima,
  • Toshiyuki Suzuki,
  • Satoshi Nagai

摘要

In May–July 2023, diarrhetic shellfish toxin (DST) exceeding the regulatory limit was detected in shellfish from Kyoto for the first time, and the dominant toxin was dinophysistoxins-3 (DTX3). The toxic marine dinoflagellate Dinophysis, including D. acuminata, D. caudata and D. fortii, was observed. To identify the potential cause of the DST occurrence, unialgal cultures of the three species were isolated from Miyazu Bay to investigate their growth characteristics and toxin production. Additionally, 36 strains of D. fortii were incubated for a month for toxin analyses. In the growth experiment, D. acuminata showed the highest specific growth rate (µ) of 0.32 ± 0.033/day, followed by D. caudata (0.23 ± 0.067/day) and D. fortii (0.20 ± 0.024/day). Toxins produced were DTX1, okadaic acid (OA) and pectenotoxin-2 (PTX2) in D. acuminata and D. fortii, and only PTX2 in D. caudata. In the stationary phase, DTX1 yield was higher in D. fortii (485.3 ± 150.07 ng/mL) compared with D. acuminata (13.8 ± 2.15 ng/mL), as was the DTX1/OA ratio (D. fortii: 61–318, D. acuminata: 0.122–0.249). Furthermore, 97% of the 35 D. fortii strains also had a high DTX1 yield (137.1 ± 81.43 ng/mL) and a high DTX1/OA ratio (26.2–9602.7). The high DTX1/OA ratio in D. fortii was similar to that observed in the highly toxic population in northern Japan that originated from the subarctic waters of the Sea of Japan and may suggest that D. fortii was the potential causative species of the DST incident in Kyoto.