The athecate dinoflagellate genus Karlodinium (Kareniaceae: Dinophyceae) from Mexican coastal waters, with three new records for the eastern Pacific Ocean

The athecate dinoflagellate genus Karlodinium (family Kareniaceae) has a relatively high diversity and is known for its potential ichthyotoxicity in coastal marine environments. In this study, we report the occurrence of four species of Karlodinium in the Mexican Pacific: K. azanzae, K. cf. elegans, K. decipiens, and K. zhouanum. Three species (K. azanzae, K. decipiens, and K. zhouanum) were isolated from Acapulco Bay in March 2023, and one species (K. cf. elegans) was detected in fixed samples collected from the western coasts of Baja California in September 2020. The cell morphology was studied mainly by light microscopy and only K. cf. elegans was examined by scanning electron microscopy. Relevant morphological characters of all studied species were consistent with previous descriptions, and their morphological identification was confirmed by phylogenetic analysis of large subunit (LSU) rDNA sequences. The synonymy of K. jejuense and K. zhouanum was proposed based on a combination of morphological and molecular data.