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Ocean Ecosystems/ESRIG, University of Groningen and Arctic Centre, University of Groningen and the RaTS program, British Antarctic Survey.

Authority

(Hust.) Jousé, in Kozlova (1962: 10, fig. 3, no. 2)

Class

Diatomophyceae

Order

Centrales

Family

Thalassiosiraceae

Synonyms

?Podosira adeliae Manguin (1960: 240, pl. 1, figs 10–12; pl. 21, figs 250, 251)

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Basionym

Coscinodiscus pseudodenticulata Hust. (Hustedt, 1958: 117, figs 20, 21)

Additional References

Jousé et al. (1962: 66, pl. 4, figs 15, 16), Priddle & Fryxell (1985: 145, figs A, B), Andreoli et al. (1995: 469, fig. 15), Hasle & Syvertsen (1997: 43, pl. 3, tab. 5)

Description

Cells solitary or attached by mucilage threads from the valve surfaces to form loose chains (Fig.d), discoid to cylindrical. Valves circular, 36–80 µm diameter; pervalvar axis 10–30 µm. Areolation radial; striae spiralling; areolae 10–16 in 10 µm, loculate, with external foramina and internal cribra. Strutted processes scattered over valve face, although sometimes sparse in the centre (Fig. d, e), 3–4 in 10 µm, simple or with short tubes from which mucilage threads emerge (Fig. d). Labiate process solitary, inside margin (Fig. f). Girdle bands with areolae similar to valves (Fig. d). Chloroplasts small, discoid, numerous.

Distribution

Sea-ice near Davis Station, East Antarctica, and Southern Ocean, south of Australia; type locality, South Atlantic Ocean and Antarctic, c. 44–69°S and 0–6°30’E (Hustedt, 1958); Weddell-Scotia Confluence (Garrison et al., 1987); Antarctic, circumpolar (Hasle, 1973); Terra Nova Bay, Ross Sea (Andreoli et al., 1995); Lützow-Holm Bay (Tanimura et al., 1990).

Comments

Specimens from Prydz Bay, photographed here, fit the descriptions of P. pseudodenticulata, but they are somewhat smaller in size and can have a higher density of areolae (10–16 in 10 µm) than was reported by other authors (10–12 in 10 µm).

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