Diversity and distribution of species of the planktonic dinoflagellate genus Alexandrium (Dinophyta) from the tropical and subtropical Mexican Pacific Ocean Author Hernández-Becerril, David U. Author Pichardo-Velarde, Jorge G. Author Alonso-Rodríguez, Rosalba Author Maciel-Baltazar, Ebodio Author Morquecho, Lourdes Author Esqueda-Lara, Karina Author Barón-Campis, Sofía A. Author Quiroz-González, Nataly text Botanica Marina 2023 Warsaw, Poland 2023-11-06 66 6 539 557 http://dx.doi.org/10.1515/bot-2023-0037 journal article 10.1515/bot-2023-0037 1437-4323 11000291 3.1.11 Alexandrium tropicale Balech ( Figures 67–69 ) Reference: Balech 1995 , 46, pl. IX, figs 11–27. Species either solitary or cells paired. Cells are rounded, small, longer than wide, with non-pronounced shoulders, excavated cingulum, not prominent apical pore, and convex hypotheca ( Figure 67 ). Plate 1′ has a very little connection with Po, and is rhomboid, larger than wide, with a ventral pore ( Figure 68 ). Po has a large foramen ( Figure 68 ). The posterior sulcal plate (Sp) is irregular and has no pore Figures 53–66: Alexandrium tamiyavanichii , LM and SEM. (53) Chain of 6 cells,LM.(54) Detail of two cells with cellular content of a chain, LM. (55) Cells in ventral view showing the anterior sulcal plate (Sa), LM. (56) Two cells slightly twisted in a chain,SEM.(57) Cell in ventral view showing plates of the ventral area, LM. (58) Empty cell in ventral view showing plate tabulation, the ventral pore is arrowed, LM. (59) Epitheca in ventro-lateral view with plate tabulation, the left sulcal list is arrowed, SEM. (60, 61) Hypotheca with plate tabulation and pore at the posterior sulcal plate (Sp),SEM.(62, 63) Po and plates around it; the ventral pore is arrowed, LM. (64) Posterior sulcal plate (Sp) with pore (arrow), LM. (65, 66) Anterior sulcal plate, LM. Figures 67–69: Alexandrium tropicale , LM. (67) Pair of cells. (68, 69) Epitheca and hypotheca with plate tabulation. ( Figure 69 ). Measurements: 28–38 μm L, 22–33 μm W (Table 1). Toxicity: this species is not considered to be toxic ( Long et al. 2021 ). Distribution: in the central Mexican Pacific.