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Authority

O.G.Kozlova (1962: 7, pl. 2, fig. 8)

Class

Diatomophyceae

Order

Centrales

Family

Thalassiosiraceae

Synonyms

N/A

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Basionym

N/A

Additional References

Fryxell & Hasle (1979a: 380, figs 1–11), Johansen & Fryxell (1985: 173, figs 5, 53–55), Fryxell & Johansen (1990: 99, pl. 11.8, fig. 1), Hasle & Syvertsen (1997: 83)

Description

Cells lightly silicified, discoid in girdle view; pervalvar axis 0.5–1.5 times cell diameter. Valves circular to slightly elliptical, 4–15 µm diameter, rounded towards the margins. Areolae in irregular radial rows, 18–24 in 10 µm; foramina partly occluded (Fig. a). Areolation on valvocopulae finer than on valve face (Fig. c). Strutted processes in a single marginal ring, 1–2 in 10 µm, operculate, each with a long internal extension (Fig. b), lacking an external extension; 1 strutted process in off-centre position; strutted processes with 4 (rarely 3) satellite pores at their base (Fig. b). Labiate process solitary, midway between 2 of the marginal strutted processes (Fig. a, b), internally slit-like and radially orientated (Fig. b).

Distribution

Coastal waters near Davis Station, East Antarctica; type locality, Indian sector of the Antarctic region between 20°E and 130°E, Second Expedition of the “Ob” (Kozlova, 1962); Antarctic and sub-Antarctic (Fryxell & Johansen, 1990); Weddell-Scotia Confluence (Garrison et al., 1987); Antarctic zones of the Weddell and Ross Seas and the Indian Ocean (Fryxell & Hasle, 1979a).

Comments

Small cells (4–10 µm diameter) usually have only 2 or 3 marginal processes, but larger cells (13–15 µm diameter) can have 5 or 6 (Fryxell & Hasle, 1979a).

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