The diatom Minutocellus polymorphus is a widely studied species because it is an ideal model for toxicity tests since it grows rapidly. Although the gross morphology has been extensively described, the ultrastructural characters associated with its importance, are unknown. It is also the only species in the genus that has been documented in the North American Atlantic, but unknown on the Eastern Pacific coasts. In a collection made in Acapulco Bay, Guerrero, Mexico, cells morphologically identical to M. polymorphus were isolated. From cultures and observations in transmission electron microscope, a first description of the ultrastructure of the genus is provided, and from sequences of 18S, we confirmed its taxonomic identity as M. polymorphus. However, more detailed studies are needed to continue increasing the knowledge about the ultrastructure of diatoms on the Mexican Pacific coasts, where they are previously unknown.

Algae constitute a non-natural group of organisms that share morphological, physiological and ecological characteristics due to a complex shared evolutionary history. They live attached to a substrate or floating in a column of fresh or marine water. These latter are classified into macro and microalgae, whose current diversity recorded in Mexico is represented by approximately 1,700 species of macroalgae and 1,500 of microalgae. However, this diversity is based on morphological attributes. The problem of the morphospecies is that it depends on the expression of the genotype in response to the environmental heterogeneity in which these organisms establish themselves, resulting in phenotypic plasticity or morphological monotony, with the consequent overlapping of characters, generating misidentifications with several taxonomical problems associated and unstable classification systems. The molecular characterization of species has generated great taxonomic changes and more robust classifications. Currently, the diversity of Mexican phylospecies is reduced, with only 250 macro and microalgae, representing 12.5 and 2.3 % of the diversity, respectively. However, of the 142 works associated with phylospecies, 82 have led to taxonomic changes and proposals with important implications in the construction of more stable classification systems and a better understanding of Mexican phycofloristic diversity in all groups.

The genus Eutreptiella (Euglenophyceae/Euglenozoa) comprises unicellular organisms known for their photosynthetic capacity and significant role in marine ecosystems. This review highlights the taxonomic, ecological, and biotechnological characteristics of Eutreptiella species, emphasizing their morphological and genomic adaptations. Eutreptiella species exhibit high phenotypic plasticity, enabling adaptation to various environmental conditions, from nutrient‐rich waters to high‐salinity conditions. They play a crucial role in primary production and nutrient cycling in marine ecosystems. Genetic and transcriptomic studies have revealed their complex regulatory mechanisms and potential for biofuel and nutraceutical production. Eutreptiella blooms significantly impact local ecosystems, influencing nutrient availability and community dynamics. Additionally, interactions with associated bacteria enhance their growth and metabolic capabilities. The genus shows substantial genetic variability, suggesting potential misidentifications or a polyphyletic nature. Further comprehensive studies are needed to clarify their taxonomy and evolutionary relationships. Understanding and managing Eutreptiella populations is essential to leverage their biotechnological potential and ensure the health of marine ecosystems.

Se reportan nuevos registros de zooplancton en el Pacífico tropical mexicano, con un énfasis particular en apendicularias. Las muestras se recolectaron entre enero de 2023 y junio de 2024 en diversas localidades utilizando redes de plancton, así como técnicas de ADN ambiental y filogenia molecular para la identificación precisa de ciertas especies. Se determinó un total de 12 nuevos registros para el Pacífico mexicano y tres registros específicos en ciertas áreas, incluyendo especies de los géneros Pseudevadne, Penilia, Appendicularia, Fritillaria y Oikopleura. Entre los hallazgos, destaca la primera caracterización molecular de Oikopleura dioica en México, revelando alta similitud genética con poblaciones japonesas, lo que subraya la distribución compartida entre la parte nororiental y noroccidental del Océano Pacífico. El nuevo registro de dos subespecies del género Fritillaria para México y el hallazgo de preferencias entre aguas oceánicas y costeras de los géneros Oikolpeura y Fritillaria. Este estudio no solo amplía el conocimiento sobre la riqueza y distribución de estos organismos en el Pacífico tropical mexicano, también proporciona una base sólida para futuras investigaciones en taxonomía, ecología y biogeografía de apendicularias y otros zoopláncteres, así como enfatizar en las posibles limitantes en el conocimiento de estos grupos. Los resultados obtenidos subrayan la necesidad de realizar estudios específicos con mayor esfuerzo de muestreo en diferentes escalas espaciales y temporales para entender mejor la biodiversidad marina de esta región. Asimismo, se recomienda el uso de técnicas moleculares para mejorar la precisión en la identificación y comprensión de la dinámica de las comunidades zooplanctónicas.

Levanderina fissa, a globally distributed mixotrophic dinoflagellate, is known for its ability to photosynthesize and phagocytize microorganisms. This study aims to approximate the phylogenetic position and explore the morphological variability of L. fissa in Acapulco Bay, Mexico, while providing observations on its diatom feeding behavior. Phylogenetic analysis based on 28S and 18S ribosomal DNA sequences suggests the existence of a monophyletic group within the Gymnodiniales, though with low phylogenetic resolution, indicating potential cryptic species within the genus. Morphological analysis reveals variability that may be influenced by regional environmental factors. Observations on diatom ingestion provide further, albeit limited, insights into the mixotrophic behavior of L. fissa. These findings emphasize the need for further research to better understand the species' ecological role and phylogenetic position, particularly concerning its feeding strategies in tropical ecosystems.

Levanderina fissa, a globally distributed mixotrophic dinoflagellate, is known for its ability to photosynthesize and phagocytize microorganisms. This study aims to approximate the phylogenetic position and explore the morphological variability of L. fissa in Acapulco Bay, Mexico, while providing observations on its diatom feeding behavior. Phylogenetic analysis based on 28S and 18S ribosomal DNA sequences suggests the existence of a monophyletic group within the Gymnodiniales, though with low phylogenetic resolution, indicating potential cryptic species within the genus. Morphological analysis reveals variability that may be influenced by regional environmental factors. Observations on diatom ingestion provide further, albeit limited, insights into the mixotrophic behavior of L. fissa. These findings emphasize the need for further research to better understand the species' ecological role and phylogenetic position, particularly concerning its feeding strategies in tropical ecosystems.