This review presents a detailed analysis of the state of knowledge of studies done in Mexico related to the dinoflagellate Gymnodinium catenatum, a paralytic toxin producer. This species was first reported in the Gulf of California in 1939; since then most studies in Mexico have focused on local blooms and seasonal variations. G. catenatum is most abundant during March and April, usually associated with water temperatures between 18 and 25 ºC and an increase in nutrients. In vitro studies of G. catenatum strains from different bays along the Pacific coast of Mexico show that this species can grow in wide ranges of salinities, temperatures, and N:P ratios. Latitudinal differences are observed in the toxicity and toxin profile, but the presence of dcSTX, dcGTX2-3, C1, and C2 are usual components. A common characteristic of the toxin profile found in shellfish, when G. catenatum is present in the coastal environment, is the detection of dcGTX2-3, dcSTX, C1, and C2. Few bioassay studies have reported effects in mollusks and lethal effects in mice, and shrimp; however no adverse effects have been observed in the copepod Acartia clausi. Interestingly, genetic sequencing of D1-D2 LSU rDNA revealed that it differs only in one base pair, compared with strains from other regions.

In this review we summarize the current state of knowledge regarding taxonomy, bloom dynamics, toxicity, autoecology, and trophic interactions, of saxitoxin producing dinoflagellates in this region. The dinoflagellates Gymnodinium catenatum, Pyrodinium bahamense and several species of Alexandrium are saxitoxin producers, and have been responsible of paralytic shellfish poisoning in different regions of Latin America, causing intoxications and important fisheries losses. The species distribution differ; most harmful algal blooms of G. catenatum are from the northern region, however this species has also been reported in central and southern regions. Blooms of P. bahamense are mostly reported in North and Central America, while blooms of Alexandrium species are more common in South America, however this genus is widely spread in Latin America. Species and regional differences are contrasted, with the aim to contribute to future guidelines for an international scientific approach for research and monitoring activities that are needed to increase our understanding of paralytic toxin producing dinoflagellates in this region.

Laboratory studies were performed to determine the effect of temperature, salinity, seawater sources and culture media on the vegetative growth of clonal cultures of Gymnodinium catenatum isolated from Bahía Concepción, Mexico. These isolates were heterothallic and isogamous. Exponential growth rates of G. catenatum in f/2 with different selenium concentrations and soil extract and GSe media were moderate. Maximum cell yields were obtained in GSe and f/2 media with selenium (10⁻⁸ and 10⁻⁷ M), while in f/2 medium with soil extract cell yields were considerably lower. The highest percentage of long chains was found in f/2 media supplied with selenium (10⁻⁸ M). The optimal temperature range for growth was 11.5–30°C, with the highest growth rates between 21 and 29°C. The range of salinity tolerated by G. catenatum changed with seawater source. With seawater from Vineyard Sound (Massachusetts, USA), G. catenatum grew at salinities from 15 to 36, with an optimal growth rate obtained at salinities between 26 and 30. With seawater from Bahía Concepción, this species tolerated salinities from 25 to 40, with optimal growth at salinities between 28 and 38. Ecophysiological measurements reported here are consistent with the environment of the bay, which has limited input of humic materials from runoff and high salinity and temperature. These data, when viewed with data from studies of globally distributed G. catenatum, demonstrate the ability of this species to live in a broad array of habitats.