Alexandrium Halim 1960

3.1.1 Alexandrium a ffi ne (Inoue et Fukuyo) Balech (Figures 2–8)

References: Balech 1995, 55, pl. XIII, figs 20–36; Usup et al. 2002, 267, figs 2 A–D; Gu et al. 2013, 72, figs 2 A–D; Lassus et al. 2016, 42, pl. 2 A–E; Kim et al. 2017, 428, figs 1 A–L.

Synonyms = Protogonyaulax affine Inouye et Fukuyo

Chain-forming species, with chains of 3–8 cells observed (Figures 2 and 3). Individual cells of medium-size, slightly longer than wide (Figures 2 and 3). The epitheca is domed to conical, cingulum excavated and the hypotheca is concave (Figure 4). The first apical plate (1′) is rhomboidal, in contact with Po, and with a small ventral pore on its right margin (Figures 5 and 6). The apical complex pore is conspicuous, with a large connecting pore and a relatively small foramen, both aligned in the same axis (Figures 6 and 7). The posterior sulcal plate (Sp) has a small pore and the two anterior ends are projected (Figure 8).

Measurements: 30–43 µm length (L), 33–43 µm width (W) (Table 1).

Toxicity: this is a species that produces saxitoxins at very low concentrations, so they do not represent a risk of poisoning (Kim et al. 2023).

Distribution: in the southern part of the Gulf of California.