Tuesday May 6, 2025, 5 pm GMT+2 (CEST)

Uriel T. Ruíz-García¹, María Luisa Núnez-Resendiz², María Eugenia Zamudio-Resendiz², Yuri B. Okolodkov³

Recent progress and emerging tools in athecate dinoflagellate classification and phylogeny

¹ Master's degree in Biology, Department of Hydrobiology, Autonomous Metropolitan University, Mexico City, 09340, Mexico
² Area ofComparative Phycology, Department of Hydrobiology, Autonomous Metropolitan University, Mexico City, 09340, Mexico
³ Marine Botany and Planktology laboratory, Institute of Marine Sciences and Fisheries, Universidad Veracruzana, Veracruz, 94294, Mexico

Dinoflagellates without cellulose in the cortical alveoli represent a diverse and complex group of organisms. Their fragility during fixation, complex life cycles, and difficulty in cultivating some species, coupled with the absence of stable morphological characters across higher taxa, have made their study a slow process compared to the much more studied thecate dinoflagellates. Traditional taxonomy has focused on variable characteristics such as the position of the cingulum and the number of turns around the cell, plastid types, nucleus position, and, more recently, the shape of the apical groove, which is stable enough for phylogenetic reconstruction in a handful of cases. The advent of molecular phylogeny has helped begin uncovering the diversity and relationships between groups beyond what a morphological approach has allowed. From molecular analyses it has been found that the largest group within the free-living athecate dinoflagellates, the Gymnodiniales, is polyphyletic and has been split into multiple groups, such as the Amphidiniales, Suessiales, Tovelliales, and many groups of uncertain placement. The absence of genetic sequences in GenBank complicates the evolutionary reconstruction and taxonomic classification of species. However, new studies are constantly providing new data that will allow for a more robust reconstruction of the phylogeny.