Molecular identification of Alexandrium pseudogonyaulax from Bahía de La Paz, Mexico

The Gulf of California is recognized as an area with a high primary productivity. Dinoflagellate species of the genus Alexandrium such as A. catenella and A. ostenfeldii, that produce hydrophilic and lipophilic toxins inhabit in this region. In April 2019, from a water sample collected in southern Bahía de La Paz individual cells were identified morphologically as Alexandrium pseudogonyaulax. To corroborate the identification, monoclonal cell cultures were grown in GSe medium, at 24 ± 1 °C at a salinity of 34, under a 12:12 h L:D cycle at 150 μmol photons m-2 s-1. Molecular identification was performed amplifying rDNA regions: 28S, 18S and 5.8S, with rDNA universal primers. The length of the sequences was 682 bp, 1657 bp, and 493 bp, respectively. Maxima Parsimony, Maximum Likelihood, and Bayesian Inference algorithms were used to perform phylogenetic analyzes. The best substitution model selected for 28S and 5.8S was TrN+G, and GTR+G for 18S sequences. The sequences of BP0419 strain from Bahía de La Paz fell within the A. pseudogonyaulax clade. These isolates also produced goniodomin A (0.23 pg cell-1), a lipophilic toxin with hemolytic activity, and is the primary reason this species is suspected of being ichthyotoxic. In coastal waters of Mexico A. pseudogonyaulax has been reported in the Pacific coast and the Gulf of California, although these previous studies did not confirm the species identification molecularly. The toxicity in animal and cellular models, as well as the allelopathic interactions between this strain and other microorganisms will be determined in future studies