Unarmored dinoflagellates in the Kareniaceae are known to be harmful to a variety of marine organisms due to their toxicity. In 2021, a red tide dominated by Karenia selliformis, along with a few occurrences of K. mikimotoi, K. longicanalis, and Takayama spp., caused the death of fish and sea urchins along the Pacific coast of Hokkaido, Japan. In our present study, brevetoxins (PbTxs) and cyclic imines (CIs) in kareniacean culture strains collected from the Pacific coast of Hokkaido and Mutsu Bay in northern Japan were analyzed using selected reaction monitoring (SRM) liquid chromatography-quadrupole tandem mass spectrometry (LC/MS/MS). PbTxs and CIs were not detectable in the kareniacean cultures collected from the red tide along the Pacific coast of Hokkaido in 2021. The K. selliformis strains isolated from Hokkaido in 2021 were closely related to those isolated from the coasts of Kamchatka and Chile based on molecular phylogenetic analysis. Interestingly, K. selliformis from Kamchatka and Chile exhibited high toxicity to some marine organisms. On the other hand, K. selliformis cultured strain MoKr600 from the Mutsu Bay produced GYM-A and B/C of CIs. This strain belonged to the same intraspecific phylogenetic group of K. selliformis that produces GYM in New Zealand. Our findings suggest that toxin production and intraspecific phylogeny are closely related in K. selliformis.
Uchida et al. (Fri,) studied this question.