Home / Diatoms / Pennate / Unicells / Biraphes / Asymmetric / Gyrosigma
Click on images for larger format
Name derivation:
Greek Gyro meaning round; sygma meaning curved.
Classification:
Gyrosigma Hassall, 1845: 435; 69 of 156 species descriptions are currently accepted taxonomically (Guiry and Guiry 2014). Order Naviculales; Family Pleurosigmataceae
Morphology:
Cells are solitary or can occasionally be enclosed in a mucilage tube with other cells. Generally lyes in valve view. It has two large plastids per cell, one against each side of the girdle. In valve view the cells are ln valve view the cells are linear and curve to a rounded point at each end opposite of eachother. The raphe is generally in the middle of the cell with a central nodule.
Similar genera:
Pleurosigma differs in that its punctae are in a diamond shaped pattern rather than the laterally striated pattern of Gyrosigma. The difference in pattern is often difficult to see with light microscopy at x400.
Habitat:
Found attached to fine sand or mud (epepelic), in brackish waters extending into marine habitats. Some species are also common in freshwater.
References:
Guiry, M.D. and G.M. Guiry 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 2 May 2014. Round, F. E., Crawford, R. M., Mann, D. G. 1990. The Diatoms. Cambridge University Press. New York, NY.