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Authority

(Ehrenb.) Hasle & P.A.Sims (1986: 111, figs 18–27)

Class

Diatomophyceae

Order

Centrales

Family

Coscinodiscaceae

Synonyms

Coscinodiscus symbolophorus Grunow (1884: 82, pl. 4, figs 3–6)
Coscinodiscus adumbratus Østrup (1895: 461, pl. 8, fig. 90)
Coscinodiscus furcatus G.Karst. (Karsten, 1905: 82, pl. 4, fig. 7), Manguin (1960: 247, pl. 24, figs 288–290), Priddle & Fryxell (1985: 134, figs A–C)
Coscinodiscus pentas (Ehrenb.) A.Mann (1907: 256)
Coscinosira stellaris (Roper) Heiden var. symbolophora (Grunow) Heiden, in Heiden & Kolbe (1928: 471)
Coscinodiscus (symbolophorus var.?) signatus A.Mann (1937: 46, pl. 4, fig. 8)
Podosira liotardii Manguin (1960: 241, pl. 21, figs 252–254)
Symbolophora furcata (G.Karst.) V.A.Nikolajev (1983: 1126, pl. 1, figs 8, 9)

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Basionym

Symbolophora microtrias Ehrenb. (Ehrenberg, 1844b: 205)

Additional References

Syvertsen (1985: 113–115, figs 1–14), Fryxell (1989: 11); Hasle & Syvertsen (1990b: 109, pl. 13.1, figs 1, 2), Moisan & Fryxell (1993: 293), Hasle & Syvertsen (1997: 113, pl. 19)

Description

Vegetative cells solitary or chain-forming (see Fryxell, 1989), discoid to lenticular, attached to sibling cells at the centre or off-centre. Valves flat to slightly convex, circular, 35–105 µm diameter; centre of valve hyaline, with a ring of up to 8 labiate processes; processes slit-like externally (Fig. d), but internally raised and elongated (Fig. e, f); marginal processes absent. Areolae arranged in furcate radial striae, 11–16 in 10 µm, loculate, externally simple or with cribra, internally with foramina. Chloroplasts numerous, irregular. Resting spores 40–100 µm diameter, with 3–5 central labiate processes; areolae fasciculate, 9–11 in 10 µm. See Syvertsen (1985) for details of resting spore formation.

Distribution

Type locality, Antarctic sea-ice, 78°10’S 162°W; Haakon VII Sea, 69°05’S 04°25’W and 69°43’S 06°30’E (Hustedt, 1958); Weddell Sea (Fryxell, 1989); near Syowa Station, East Antarctica (Watanabe et al., 1990; Ishikawa et al., 2001); southern cold waters (Hasle & Syvertsen, 1997); Scotia Sea (Garrison et al., 1987).

Comments

Stellarima differs from Coscinodiscus in lacking marginal labiate processes, and in having internal closing plates to the areolae (Round et al., 1990). Resting spores are common in ice samples and in net samples from the vicinity of ice (Hasle & Syvertsen, 1990b). Hasle & Syvertsen (1997) observed that “Stellarima mictrotrias forms heavily silicified endogenous resting spores, usually identified as Coscinodiscus symbolophorus”.

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