ABCDEFGHIJKLMNOPQRSTUVWXYZ

     

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

Authority

(Hasle) Hasle (1993: 317)

Class

Diatomophyceae

Order

Pennales

Family

Bacillariaceae

Synonyms

Fragilaria nana Steem.Neils., in Holmes (1956: fig. 17a, pro parte), Paasche (1961: 201, pl. 1a, fig. 1a), Hasle (1964: pl. 3, fig. 2)
See Hasle (1965b) for full synonymy, LM and EM descriptions and discussion of nomenclatural problems.

top

Basionym

Nitzschia pseudonana Hasle (1974: 427), Hasle & Medlin (1990c: 181, pl. 24.1, figs 7–14; pl. 24.2, figs 20, 21; pl. 24.8, figs 1–3)

Additional References

Hasle (1965b: 22: pl. 1, figs 7–14; pl. 4, figs 20, 21; pl. 8, figs 1–9; pl. 17, fig. 6), Moisan & Fryxell (1993: 493), Kang & Lee (1995: 260, fig. 6C), Hasle & Syvertsen (1997: 300, pl. 67)

Description

Cells solitary or in short chains with cells attached by valve faces, elliptical to lanceolate in valve view; larger valves with slightly elongated ends; apical axis 4–20 µm; transapical axis 2.5–5 µm. Transapical striae straight in the middle of the cell, curved near the valve poles, 18–28 in 10 µm. Canal raphe markedly eccentric (Fig. b). Fibulae present in the same number as striae, arcuate, fastened to valve near striae and valve mantle; no indication of a greater distance between the 2 fibulae in the middle. Interstrial membranes perforated by 2 rows of minute areolae, 6–8 in 10 µm, situated close to striae. Outer canal wall without areolae. Pseudonodulus absent; terminal nodules present.

Distribution

Southern Ocean, south of Australia; Drygalski Glacier, Ross Sea; BRATEGG sample, brownish undersurface of pack-ice, 62°30’S, 19°42’W (Hasle, 1965); KERFIX, 50°40’S 68°25’E, Southern Ocean (Kopczyńska et al., 1998); Bransfield Strait (Kang & Lee, 1995); Weddell-Scotia Confluence (Garrison et al., 1987).

Comments

Fragilariopsis pseudonana is also known from cold northern waters (Denmark Strait, 62°N 33°W and 60°18’N 31°00’W; Shetland Is., 61°08.5’N 02°21’W) as well as warmer regions (Gulf of California, Gulf of Panama, Wellington Harbour; Hasle, 1965b). Due to the similarity of cell shape and striation, it is difficult to separate F. pseudonana from small specimens of F. cylindrus. See discussion under F. cylindrus. Generally, Fragilariopsis pseudonana cells are elliptical-lanceolate -valved, whereas (small specimens of ) Fragilariopsis cylindrus  are linear-valved.

 

top