Home / Diatoms / Pennate / Unicells / Biraphes / Asymmetric / Keeled / Nitzschia
Click on images for larger format
Name derivation:
Classification:
Nitzschia Hassall 1845 Order Bacillariales; Family Bacillariaceae Synonym Simonsenia Lange-Bertalog 1979
Morphology:
The cells are usually elongated and in valve view its outline can vary widely. The valves can be straight to sigmoid and can lye in either valve or girdle view. In valve view the center can be slightly swollen with rounded edges at each pole. The keeled margin on one valve faces the margin of the other cell with no keel and the keel appears to cross the cell diagonally. Striations are occur along the valve face of the cell. The cells can be unicellular or form chain like colonies, sometimes forming within muscilage tubes.
Similar genera:
Nitzschia is similiar to Hantzschia, but differs in that the frustules of Nitszchia are square instead of rectangular in girdle view. The keeled margins of a pair of valves are diagonal to eachother instead of being opposite eachother like Hantszchia. Simonsenia was recognized as a separate genus with morphology midway between Nitzschia and Surirella (Lange-Bertalog 1979), but is not separated in PhycoKey
Habitat:
Freshwater or marine; can be epiphytic on sand or planktonic.
Toxicity:
Nitzschia navis-varingica has been found to produce domoic acids in the vicinity of Japan, Philippines, Vietnam and Australia. Mainly in tropical to subtropical marine waters.
References:
Hassall, A.H. 1845. A history of the British freshwater algae, including descriptions of the Desmideae and Diatomaceae. With upwards of one hundred plates, illustrating the various species.... pp. vol 1: [i]-viii, [i]-402, [ i , err.]; vol. 2: p. [i]-24, pl. 1-103 (55 as 'lvi'). London, Edinburgh, Paris & Leipzig: S. Highley, H. Baillière; Sunderland & Knox; J.B. Baillière; T.O. Weigel. Lange-Bertalot, H. 1979. Simonsenia, a new genus with morphology intermediate between Nitzschia and Surirella. Bacillaria 2: 127-136. Round, F. E., Crawford, R. M., Mann, D. G. 1990. The Diatoms. Cambridge University Press. New York, NY. Smith, Gilbert, 1950. The Fresh-Water ALgaie of the United States. McGraw-Hill Book Company, Inc. New York, NY.