Molecular Assessment of Athecate Dinoflagellates of the Order Gymnodiniales (Dinophyceae) in Todos Santos Bay, Baja California México

Abstract

The Gymnodiniales are the most important group of athecate dinoflagellates both for its abundance and distribution and for the harmful potential of several of its species. Although morphologically it is well known, phylogenetically it has been very little studied. HABs impact important coastal activities in Todos Santos Bay, so a detailed characterization of potentially toxic phytoplankton species is crucial in monitoring surveys. Therefore, the aim of the present study was to carry out a molecular assessment to the morphospecies of Gymnodiniales currently recorded in Todos Santos Bay, from which discussed their phylogenetic relationships. 120 samples were obtained from monthly samplings during 2019 to 2020. For all of them, 18 s small subunit (SSU) and 28 s large subunit (LSU) genes of rDNA were amplified and sequenced using single-cell PCR. Also, they were photographed. A phylogenetic analysis was performed on MrBayes from the combined 18 s -28 s data set. The presence of 15 phylogenetic entities was confirmed, four of which constituted new records for the Mexican Pacific, as well as three harmful species, one toxic and two bloom-forming. Our molecular results evidenced the need to re-evaluate the current taxonomic system of athecate dinoflagellates at all hierarchical levels, integrating them with morphological evidence without preponderance of this criterion over taxonomic decisions.

First record of the genus Togula (Gymnodiniales, Dinophyceae) and of the species T. jolla for the South-West Atlantic coastal waters

“…The unarmored species are distinguished by size, shape and contour of the cells, relative sizes of epicone and hypocone, position and morphology of the cingulum and sulcus, displacement of the cingulum in relation to the cell length, presence/absence of chloroplasts and pyrenoids, shape and position of the nucleus, presence/ absence of surface striations, features observed with light microscopy (LM); presence/absence of apical groove, shape of the apical groove, ultrastructural features observed with scanning electron microscopy (SEM); vesicular chambers in the nuclear envelope, presence/absence of nuclear fibrous connector, among other complex ultrastructural features observed with transmission electron microscopy (TEM) (Daugbjerg et al, 2000;Larsen & Nguyen, 2004;Hoppenrath et al, 2009;Reñé et al, 2011;Escarcega-Bata et al, 2021). This group of dinoflagellates is more delicate than thecate ones and frequently do not maintain their shape, deteriorate or destroy when the sample is preserved with the most frequently used fixatives, thus species only can be detected in live samples.…”

“…When working with live samples, the most robust species are kept in good condition during the analysis by light microscopy, while other more delicate ones deteriorate during observation (Larsen, 2002). This characteristic explains the very limited knowledge of a great part of the gymnodinoid dinoflagellates (Larsen & Nguyen, 2004;Gómez et al, 2011;Escarcega-Bata et al, 2021.…”

Diversidad de dinoflagelados atecados del orden Gymnodiniales (Dinophyceae), con énfasis en aquellos formadores de florecimientos algales nocivos en las costas del Pacífico Mexicano

“…Esto ha generado un problema que con el tiempo llevó a los taxónomos a realizar identificaciones o descripciones incorrectas de las diferentes especies atecadas (Escarcega-Bata et al, 2022). A pesar de los esfuerzos de identificación a través de múltiples técnicas de microscopía, no ha sido posible conocer la diversidad real del grupo, debido a que estos organismos presentan un ciclo de vida complejo y una plasticidad fenotípica alta (Reñé et al, 2015;Gárate-Lizárraga, 2020;Escarcega-Bata et al, 2021). A partir de la década de 1990, se comenzaron a abordar nuevas técnicas de identificación en dinoflagelados mediante la extracción y amplificación de ADN ribosómico, pero esto solo era posible con especies disponibles en cultivos monoclonales (Hinnebusch et al, 1981).…”

“…2), la diversidad de dinoflagelados atecados se conoce exclusivamente con base en su morfología (Licea et al, 1995;Esqueda-Lara y Hernández-Becerril, 2010;Meave del Castillo et al, 2012;Almazán-Becerril et al, 2016;Gárate-Lizárraga, 2020;Escarcega-Bata et al, 2022). Adicionalmente, el único estudio de evaluación molecular en especies atecadas es el realizado por Escarcega-Bata et al (2021), donde se detectó mediante marcadores moleculares (genes 18S y 28S del ADNr), un problema en la clasificación actual de varias familias del orden Gymnodiniales, a partir de muestras colectadas en Bahía Todos Santos, Baja California. El objetivo de este estudio fue realizar un listado florístico a partir de una revisión bibliográfica, que integre únicamente a los registros respaldados por micrografías, para conocer la diversidad de dinoflagelados atecados del orden Gymnodiniales distribuidos a lo largo del PM, con énfasis en aquellos formadores de florecimientos algales nocivos.…”