Aulacoseira nyassensis

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SPECIES Aulacoseira nyassensis
(Müller) Simenson (1979)

Taxonomic Information

Jr. Synonymy:

  • Melosira nyassensis Müller (1904)
Morphometry:
     Diameter: 20-35 µm
     Height: 9.5-29 µm
     Pore Rows: 8-9 in 10 μm
     Pores: circular or elliptical, 6-8 in 10 μm
Species Description:

Müller (1904)

Valve cylindrical, valve mantle is rectangular with straight sides and weakly rounded corners. Valve face is circular, flat, the valve faces of sibling cells are closely attached, the edges of the valve face are slightly separated from each other forming a small pseudosulcus. The valve face is covered with pores; the edges are studded with small spines that alternate with the ones across from them. Threaded segments are closely connected to their neighbors. Rows of areolae along the valve mantle are sometimes parallel to the pervalvar axis, sometimes run in steeply slanted spirals across the axis in distances of 8-9/10µm, and sometimes they run crosswise. Mantle areolae are coarse, circular or elliptical, with densities of 6-8/10 µm per row. Cell walls are thick, the inner mantle line is straight; the sulcus forms as a narrow groove; the collum is longer and funnel-shaped. Ratio of diameter to height: 1: 0.38-1.1. Length of colonies, up to 12.5 members observed. Terminal valves never have separation spines (visible in LM). [Translated from Müller's original description by jrs]

Original drawings from Müller (1904)

SEM of A.nyassensis from Lake Malawi - courtesy jrs

  • Demographic Information: Tropical East Africa
  • Stratigraphic Information: At least Pleistocene to modern.
  • Ecologic Information: Meroplanktic; freshwater.

Useful References

  • Müller, O., 1904. Bacillarien aus dem Nyassalande und einigen benachbarten Gebieten. Zweite Folge. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie 34, 256-301.
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