Variations of PSP toxin profiles during different growth phases in Gymnodinium catenatum (Dinophyceae) strains isolated from three locations in the Gulf of California, Mexico

In vitro experiments were performed with Gymnodinium catenatum Graham strains isolated from three locations in the Gulf of California to determine the variability in toxicity and toxin profiles. Strains were cultivated in GSe at 20°C ± 1°C, 150 μmol photons·m ^-2·s^-1 (12:12 light:dark cycle), and harvested during different growth phases. Growth rates were higher than in previous studies, varying between 0.70 and 0.82 day^-1. The highest cell yields were reached at 16 and 19 days, with maximum densities between 1090 and 3393 cells· mL^-1. Bahía de La Paz (BAPAZ) and Bahía de Mazatlán (BAMAZ) were the most toxic (101 pg STXeq·cell ^-1), whereas strains from Bahía Concepción (BACO) were the least toxic (13 pg STXeq·cell^-1). A strain isolated from cyst germination was one of the least toxic strains. No significant changes in toxin content with culture age were observed (0.2 and 0.6 pmol paralytic shellfish poisoning·cell^-1). All strains contained neosaxitoxin (NEOSTX), decarbamoyl-saxitoxin (dcSTX), decarbamoyl-gonyautoxin-2, -3, (dcGTX2-3), N-sulfocarbamoylsaxitoxin (B1), N-sulfo-carbamoylneosaxitoxin (B2), and N-sulfo-carbamoylgonyautoxin-2,-3 (C1-2). Bahía Concepción strains had the highest content of C1; BAPAZ and BAMAZ strains had a higher percentage of NEOSTX. Differences in toxin composition with culture age were observed only in BAMAZ and BAPAZ strains. Cultures with a higher percentage of long chains had more NEOSTX, while those with a higher proportion of short chains had a lower content of NEOSTX. Gulf of California strains are characterized by a high proportion of NEOSTX, and seem to have evolved particular physiological responses to their environment that are reflected in the toxin profile, suggesting different populations.