Fragilaria spinosa Skvortzow 1937




Collection 1395

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Skvortzow, B.W., Philippine Journal of Science 37: 307, figs. 13 and 27, plate 4, fig 13, figs. 3 and 19, pl. 5, 54-59. 1937.

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The valve outline is highly variable from linear/elliptical to lanceolate. The valves are often gibbous near the midportion of the valve(Stoermer and Yang 1969). The striae are coarse and chambered and do not extend past the midline of the valve(Stoermer and Yang 1969). The axial area is broad and lanceolate with no visible structure and no distinct central area(Stoermer and Yang 1969). There are distinct submarginal spines extending out between each striae which hold the frustules together in band-like colonies (Skvortzow 1937a). Compared to Lake Baikal specimens, specimens from Great Lakes have much narrower valve widths. The ratio is 1/5 or 1/6 rather than 1/3.5 to 1/5 (Stoermer and Yang 1969). However, the valves have similar ornamentation. This species was compared to Fragilaria robusta Hustedt nom. nud. [not Fragilaria robusta sensu (Fusey) Manguin] (Skvortzow 1937a).
  • Synonyms (Stoermer and Yang 1969)
    Fragilaria mutabilis var. robusta Skvortzow and Meyer 1928.
  • Ecology This species was rare in samples from the Great Lakes and was generally in the periphyton community from deep water samples (Stoermer and Yang 1969).

    Size ranges and morphology

    In Lake Michigan samples:
    The length ranges from 25-46 micrometers (Stoermer and Yang 1969).
    The width ranges from 5-8 micrometers (Stoermer and Yang 1969).
    The striae range from 5-8 in 10 micrometers (Stoermer and Yang 1969).