Francisco Eduardo Hernández-Sandoval

Effect of temperature on growth and paralytic toxin profiles in isolates of Gymnodinium catenatum (Dinophyceae) from the Pacific coast of Mexico

The effects of temperature on growth, cell toxicity, toxin content, and profile of paralytic shellfish toxins was determined in eight isolates of Gymnodinium catenatum from several localities along the Pacific Coast of Mexico. The isolates were cultivated in modified f/2 media with Se (10(-8) M), and a reduced concentration of Cu (10(-8) M), under a 12 h:12 h day-night cycle with an irradiance of 150 μE m(-2) s(-1). Isolates were progressively adapted for three generations to each of the temperatures (16, 19, 22, 24, 27, 30, and 33 °C). The cultures were grown in 125 mL Erlenmeyer flasks with 60 mL of media and harvested by filtration in late exponential growth. Toxins were analyzed by HPLC with a post-column oxidation and fluorescent detection (FLD). G. catenatum isolates tolerate temperatures between 16 and 33 °C, with maximum growth rates of 0.32 and 0.39 div day(-1) at 21 °C and 24 °C, respectively; maximum cell densities of 4700 and 5500 cells mL(-1) were obtained at 27 and 21 °C, respectively. No effect of toxicity per cell with temperature was observed, varying between 10.10 and 28.19 pgSXTeq cell(-1). Ten saxitoxin analogues were detected in all isolates, observing changes in the toxin profile with temperature. C1/2 toxins decreased from 80% mol at 16 °C to 20% mol at 33 °C, B1/2 toxins increased from 19% mol at 16 °C to 42% mol at 33 °C, and decarbamoyl toxins were more abundant at 21 °C. These results show that G. catenatum isolates from different regions of the Pacific coast of Mexico have a similar response to temperature and that this parameter can modify growth rate, cell density, and toxin profile of the species, particularly the decarbamoyl and sulfocarbamoyl toxins.

Paralytic toxin profile of the marine dinoflagellate Gymnodinium catenatum Graham from the Mexican Pacific as revealed by LC-MS/MS

The paralytic shellfish toxin (PST) profiles of Gymnodinium catenatum Graham have been reported for several strains from the Pacific coast of Mexico cultured under different laboratory conditions, as well as from natural populations. Up to 15 saxitoxin analogues occurred and the quantity of each toxin depended on the growth phase and culture conditions. Previous analysis of toxin profiles of G. catenatum isolated from Mexico have been based on post-column oxidation liquid chromatography with fluorescence detection (LC-FLD), a method prone to artefacts and non-specificity, leading to misinterpretation of toxin composition. We describe, for the first time, the complete toxin profile for several G. catenatum strains from diverse locations of the Pacific coast of Mexico. The new results confirmed previous reports on the dominance of the less potent sulfocarbamoyl toxins (C1/2); significant differences, however, in the composition (e.g., absence of saxitoxin, gonyautoxin 2/3 and neosaxitoxin) were revealed in our confirmatory analysis. The LC-MS/MS analyses also indicated at least seven putative benzoyl toxin analogues and provided support for their existence. This new toxin profile shows a high similarity (> 80%) to the profiles reported from several regions around the world, suggesting low genetic variability among global populations.

Condiciones ambientales durante un florecimiento de Cochlodinium polykrikoides (Gymnodiniales, Dinophyceae) en la Ensenada de La Paz, Golfo de California

Abstract .- Environmental conditions are described during a bloom of Cochlodinium polykrikoides that occurred betweenSeptember 12 th and November 9 th 2012, in Ensenada de La Paz, Gulf of California. At the beginning of the bloom, the numberof cells, chlorophyll a , and peridinin was 6.2 x10 2 cells mL -1 , 10.1 mg m -3 , and 3.5 mg m -3 , respectively; 8.6 x 10 3 cells mL -1 ,121.2 mg m -3 and 40.2 mg m -3 in their maximum intensity; and 5 cells mL -1 , 1.02 mg m -3 of chlorophyll a , and 0.03 mg m -3 ofperidinin, at the end of the bloom period. Thermal interval fluctuated between 30.3 and 31.3 °C; salinity varied from 35.2to 36.8; dissolved O 2 ranged from 4.8 to 10.8 mL L -1 ; saturation percentage was > 200. The values of nitrate, phosphate, andthe N:P ratio at the initiation of the bloom were 1.8, 0.9 (μM) and 2.8, during the maximum intensity they were 8.5, 3.4 (μM),and 2.9. At the end of the bloom they were 5.3, 0.6 (μM) and 9.0. Prevailing winds were from the NNE (0.4-5.0 m s