Variability and species discrimination within the Protogonyaulax tamarensis/catenells species complex : toxic red-tide dinoflagellates

Thecate gonyaulacoid dinoflagellates referable to the genus Protogonyaulax Taylor cause paralytic shellfish poisoning (PSP) in coastal regions throughout the world. Isolates of the Protogonyaulax tamarensis/ catenella species complex from diverse geographical regions, including ten contemporaneous isolates from the same location, were subjected to chemotaxonomic analysis of soluble isozymes by gel electrophoresis, an analysis of toxin components using high-pressure (performance) liquid chromatography and quantitative nuclear DNA determinations by epifluorescence microphotometry. The results were compared with conventional morphological criteria used to discriminate among species, to establish taxonomic linkages and to estimate phenotypic and genotypic variation within this group. These biochemical methods, along with measurements of acclimated growth rate, offered a means of distinguishing between isolates of this species complex, for which the thecal plate patterns were substantially the same. The isozyme patterns revealed a high degree of genetic polymorphism within and among morphotypes and geographical populations. Yet, within the tamarensoid morphotype, isolates from the same location were more similar than to those from elsewhere. This general trend was supported by evidence from toxin profiles and DNA analysis, although toxin heterogeneity was a more conservative measure of variation than isozyme diversity. Protogonyaulax isolates varied markedly in total toxin concentration and toxicity, even through the culture cycle of individual isolates, but the toxin ratios were distinctive and relatively constant. The catenelloid and tamarensoid forms, the dominant morphotypes within this species complex, were not well correlated with the biochemical characters investigated. Given the occasional presence of morphological intermediates, the morphological features presently used to identify P. catenella and P. tamarensis cannot always be used to reliably discriminate between these morphospecies, and appear to be inadequate as stable species descriptors. At least two smaller isolates from allopatric populations exhibited morphological and biochemical differences large enough to indicate possible species divergence. The high level of genetic diversity reflected in the biochemical heterogeneity within populations from a given geographical area suggests that sibling species may also have arisen within sympatrically distributed Protogonyaulax populations.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat

Toxicity Bioassay and Cytotoxic Effects of the Benthic Marine Dinoflagellate Amphidinium operculatum

Benthic dinoflagellates produce a wide array of bioactive compounds, primarily polyketides, that cause toxic effects on human consumers of seafood and perhaps mediate species interactions in the benthic microenvironment. This study assesses toxic and other bioactive effects of the benthic dinoflagellate Amphidinium operculatum (strain AA60) in two targeted bioassays. The brine shrimp (Artemia salina) bioassay revealed lethal effects of direct exposure to live dinoflagellate cells (Treatment A) and even higher potency with ethanolic extracts of lysed cells (Treatment D). There were no inimical bioactive effects of components released to the aqueous growth medium (Treatment B) or from aqueous cell lysates (Treatment C). The hypothesis that released bioactive compounds provide a chemical defense against metazoan grazers is therefore not supported by these results. The cytotoxic effect of ethanolic crude extracts of this dinoflagellate exhibited mild to high growth reduction effects on six human cancer cell lines. In particular, crude cell-free extracts proved highly growth-inhibitory activity towards breast and lung cancer cell lines MCF-7 and SKLU-1, respectively. Preliminary anti-cancer results indicate that natural bioactive compounds from Amphidinium are worthy of structural characterization and further toxicological investigation as potential therapeutants

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