Montresor, Procaccani & Stoecker (1999: 187, figs 1–13, 20–22)
Buck et al. (1992), Stoecker et al. (1997: 591, fig. 5; 1998), Thomson et al. (2004: 867)
[modified from Montresor et al. (1999)] Vegetative cells: 10–15 µm long, 6–9 µm wide, with a rounded episome and a conical hyposome. Cell surface smooth, with a few small scattered protuberances; amphiesmal plates concealed by outer membrane. Cingulum deep, left-handed, displaced by c. 1 cingular width. Sulcus shallow, not extending into episome. Insertion point of flagella obscured by protrusion of the episome. Chloroplast(?s) present; it is unclear whether there is a single multilobed chloroplast or many chloroplasts converging towards the central part of the cell.
Drygalski Glacier, Ross Sea; in fast-ice near Casey, Davis and Mawson Stations and Larsemann Hills, East Antarctica (Thomson et al., unpublished data); abundant in brine pockets and channels of upper fast-ice (Stoecker et al., 1997, 1998; Thomson & McMinn, unpublished data); McMurdo Sound (Stoecker et al., 1997, 1998); pack-ice in the Indian sector of the Southern Ocean, 62°56.87’S 92°58.00’E (Thomson et al., 2004); Weddell and Scotia Seas (Garrison & Buck, 1989b; Buck et al., 1992); bipolar and circumpolar in the Antarctic (Montresor et al., 2003).
Larger cysts (to 25 µm diameter), morphologically indistinguishable from P. glacialis, have been reported from sea-ice near Davis Station and McMurdo Sound. Cysts with surface pores have been documented (e.g. Stoecker et al., 1992, fig. 9A), and Montresor et al. (1999) suggested that these cysts might be closely related species or, possibly, phenotypes of P. glacialis.