Identification of the Gene sxtA (Domains sxtA1 and sxtA4) in Mexican Strains of Gymnodinium catenatum (Dinophyceae) and Their Evolution

Saxitoxin (STX) and its analogs are a broad group of natural neurotoxic alkaloids, commonly known as paralytic shellfish toxins. SxtA is the initial gene in the biosynthesis of saxitoxin. It has been proposed that the genes for STX biosynthesis had a bacterial origin and were acquired in the dinoflagellates by a horizontal gene transfer (HGT). In Gymnodinium catenatum, the origin of the STX genes is not well established. In this paper, we sequenced sxtA gene (domains sxtA1 and sxtA4) and determined the gene copy number in the genome in four Mexican strains of G. catenatum. We compare them with sequences of G. catenatum, Pyrodinium bahamense, and Alexandrium spp. from other geographic regions, and non-toxic producing dinoflagellates. Amplifications were performed for domains sxtA1 and sxtA4 from strains of G. catenatum and the phylogenetic analyses was done by maximum likelihood and Bayesian inference. The copy number determination was carried out using qPCR. The phylogenetic tree of domain sxtA4 showed the formation of two clades where G. catenatum sequences separated from the Alexandrium/Pyrodinium clade. The domain sxtA1 formed a higher number of clades than sxtA4. Sequences of G. catenatum were grouped together with sequences of Alexandrium. Dinoflagellates sequences that do not produce saxitoxin formed a separate clade. The gene copy number was 64 ± 30 and 110 ± 50 copies of sxtA1 and sxtA4 respectively. The identification of the gene sxtA of G. catenatum shows that the sequences are similar to those of Alexandrium species with low variations between species. These results may indicate that the acquisition of the gene sxtA was an early HGT event in the evolution of dinoflagellates. The possible loss of the ability to produce STX in some species suggests that the HGT from Alexandrium species toward G. catenatum is not possible

Paralytic Toxin Producing Dinoflagellates in Latin America: Ecology and Physiology

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

Lipophilic Toxins in Wild Bivalves from the Southern Gulf of California, Mexico

Most of the shellfish fisheries of Mexico occur in the Gulf of California. In this region, known for its high primary productivity, blooms of diatoms and dinoflagellates are common, occurring mainly during upwelling events. Dinoflagellates that produce lipophilic toxins are present, where some outbreaks related to okadaic acid and dinophisystoxins have been recorded. From January 2015 to November 2017 samples of three species of wild bivalve mollusks were collected monthly in five sites in the southern region of Bahía de La Paz. Pooled tissue extracts were analyzed using LC-MS/MS to detect lipophilic toxins. Eighteen analogs of seven toxin groups, including cyclic imines were identified, fortunately individual toxins did not exceed regulatory levels and also the total toxin concentration for each bivalve species was lower than the maximum permitted level for human consumption. Interspecific differences in toxin number and concentration were observed in three species of bivalves even when the samples were collected at the same site. Okadaic acid was detected in low concentrations, while yessotoxins and gymnodimines had the highest concentrations in bivalve tissues. Although in low quantities, the presence of cyclic imines and other lipophilic toxins in bivalves from the southern Gulf of California was constant

Una revisión sobre los dinoflagelados marinos bentónicos en México: Benthic dinoflagellates in Mexico

Background. Studies on marine benthic dinoflagellates (MBD) began in 1942 from the offshore region of Oaxaca, based on water column samples. Subsequently, in ten Mexican maritime states, both epibenthos and plankton samples have been collected, species have been cultured, and field and laboratory studies have been carried out. Many of these species are related to ciguatera fish poisoning and diarrhetic shellfish poisoning. Goals. The objective of this contribution was to review the studies on MBD in Mexican waters. Methods. Available literature on MBD published from 1942 to 2022 was analyzed. Results. A review of the studies on MBD is presented, subdivided into two sections: (1) taxonomic diversity (morphological and molecular) and (2) toxigenicity and species interactions. A map of the studies on MBD, a list of taxonomic and ecological studies on MBD in Mexico and a list of ca. 60 species (mainly Prorocentrum, followed by Amphidinium, Gambierdiscus, Ostreopsis and Sinophysis) is presented, accompanied by scanning electron microscopic images of 15 species. Knowledge of the toxigenicity of MBD is still scarce. Experimental studies on MBD begun in this century have shown great potential; Prorocentrum lima has been the main object of these studies. Conclusions. Studies on MBD have slowly increased, probably due to the availability of a greater number of strains, as well as to international collaboration. Confirmed links between particular benthic harmful algal blooming species and events associated with the etiology of toxic syndromes are rare. However, the lack of reports does not indicate an absence of intoxications. Studies on toxicity, allelopathy, ecology, impact on cultivated organisms, biosynthesis of metabolites and biotechnological potential still need to be undertaken in Mexico.Antecedentes. Los estudios sobre dinoflagelados bentónicos marinos (DBM) en México comenzaron en 1942 desde la región oceánica de Oaxaca, basados en muestras de la columna de agua. Posteriormente, en diez estados costeros mexicanos se recolectaron muestras de epibentos y plancton, se han cultivado especies, y se han realizado estudios de campo y de laboratorio. Muchas de estas especies están relacionadas con la intoxicación por consumo de peces (ciguatera) y la intoxicación diarreica por consumo de mariscos. Objetivos. El objetivo de esta contribución fue revisar los estudios sobre DBM en aguas mexicanas. Métodos. Se analizó la literatura disponible sobre DBM publicada desde 1942 hasta 2022. Resultados. Se presenta una revisión de los estudios sobre DBM subdividida en dos secciones: (1) diversidad taxonómica (morfológica y molecular) y (2) toxigenicidad y relaciones entre especies. Se presenta un mapa de los estudios sobre DBM, una lista de estudios taxonómicos y ecológicos sobre DBM en México y una lista de aproximadamente 60 especies (principalmente Prorocentrum, seguido de Amphidinium, Gambierdiscus, Ostreopsis y Sinophysis), acompañado de imágenes de microscopía electrónica de barrido de 15 especies. El conocimiento de la toxigenicidad de DBM aún es escaso. Los estudios experimentales sobre DBM iniciados en este siglo han demostrado un gran potencial, y Prorocentrum lima ha sido el principal objeto de estudio. Conclusiones. Los estudios sobre DBM han aumentado lentamente, probablemente debido a la disponibilidad de un mayor número de cepas, así como a la colaboración internacional. Los vínculos confirmados entre especies particulares de florecimientos algales nocivos bentónicos con los eventos asociados con la etiología de los síndromes tóxicos son escasos. Sin embargo, la falta de informes no indica ausencia de intoxicaciones. En México aún faltan por realizar estudios sobre toxicidad, alelopatía, ecología, impacto en organismos cultivados, biosíntesis de metabolitos y potencial biotecnológico