Home / Diatoms / Pennate / Unicells / Biraphes / Asymmetric / Pleurosigma
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Name derivation:
Greek Pleuro meaning a rib; sigma meaning curved.
Classification:
Two sections of this genus are separated by striae types. One type is transverse and longitudinal striae and the other type is transverse and oblique striae (Sar 2012)
Morphology:
Cells solitary genarally lying in valve view. Valves are elongate and sigmoid (curved like an S) in shape. The valves may be only slightly curved. The raphe is also sigmoid shape sometimes more or less curved than the valve itself. Punctae are present and form striations across the valve face that appear as diagonal rows. The cell contains two to four plastids that extend from the top of the cell to the bottom.
Similar genera:
Gyrosigma is similiar in shape and appearance. It differs from Pleurosigma in the pattern of the striations on the valve face. The punctae in Gyrosigma form transverse striations accross the valve face and Pleurosigma striations form a diamond shape pattern.
Habitat:
Primarily marine genus with several species found in brackish or high conductivity water. Few freshwater species.
References:
Round, F. E., Crawford, R. M., Mann, D. G. 1990. The Diatoms. Cambridge University Press. New York, NY. Wehr, J., Sheath, R. 2003. Freshwater Algae of North America Ecology and Classification. Academis Press. San Diego, CA.