(Manton & Parke) Desikachary (1973: 447, pl. 1, fig. 1)
Barlow & Cattolico (1980: 321, figs 1–30), Hallegraeff (1983: 499, fig. 25a, b), Marchant et al. (1989: 168, figs 1–3, 7–11, 22)
Micromonas squamata Manton & Parke (1960: 293, figs 1–29)
Cells 2.7–3.5 µm diameter (dried preparation), with 2 unequal flagella arising from anterior part of cell. Body scales (140–) 240 (–330) nm diameter, with a spider’s web pattern of fibrils and a small central protuberance, with 7 radial spokes, concentric ribs not regularly spaced, gaps seen around central protuberance. Long flagellum (10–) 22 (–30) µm long; short flagellum c. 1 µm long. Flagella scales arranged in rows, apparently attached by their rims, flat, discoid, 0.18–0.26 µm diameter, patterned like body scales; flagella also sparsely decorated with hair-scales that can form a terminal tuft on the long flagellum; hair-scales c. 0.5 µm long, 30 nm diameter, tapering proximally, with a delicate cross-banded structure with a periodicity of c. 12 nm.
Pack-ice and land-fast ice, Weddell Sea (Marchant et al., 1989); Great Britain (Manton & Parke, 1960); eastern Australia (Hallegraeff, 1983); Denmark (Manton & Leadbeater, 1974); Greenland (Thomsen, 1982).
Cell dimensions and flagellar lengths are variable (Marchant et al., 1989). Scales of Antarctic specimens are the same size as those reported for the type material from Great Britain, but they differ structurally. Scales of the latter have 8 radial spokes while the Antarctic cells have 7. Moreover, concentric ribs are ±regularly spaced in the type material, less so in Antarctic populations.