Taxonomy
- Order
- Nostocales
- Family
- Aphanizomenonaceae
- Genus
- Dolichospermum
Examples of Dolichospermum
400X total magnification; 10 μm scale bar.
400X total magnification; 20 μm scale bar.
400X total magnification.
400X total magnification; 20 μm scale bar.
Morphology
Trichomes usually solitary, or in small, irregular clusters; straight, curved, or coiled; isopolar; not narrowed towards the ends; usually with clear constrictions at crosswalls; metameric. Never with firm sheaths; sometimes with fine mucilaginous envelopes. Cells spherical, barrel-shaped, or nearly cylindrical; usually isodiametric, sometimes longer than wide (up to 2x longer than wide). Terminal cells not different from other vegetative cells; rounded at the ends. Obligately with aerotopes.
Heterocytes intercalary (but can be found in a terminal position only after disintegration of a trichome); solitary; usually spherical, sometimes barrel-shaped; as wide as vegetative cells (or nearly so; slightly wider or narrower). Akinetes intercalary; solitary, or sometimes in rows of up to 5; cylindrical, ovoid, oval, or spherical in shape; developing paraheterocytically, adjacent to or slightly distant from heterocytes.
Ecology
Trichomes are planktic, or rarely metaphytic. Mostly reported in temperate zones, in freshwater mesotrophic lakes and ponds. Capable of forming surface blooms.
Note that Dolichospermum was formerly classified as a cluster of “planktic Anabaena” species; the two genera are distinct phylogenetically, morphologically, and ecologically. Unlike Anabaena, Dolichospermum is planktic, cells obligately contain aerotopes, and trichomes are mostly solitary (not forming mats).
References
- Johansen, J. R., & Komárek, J. (2015). Filamentous Cyanobacteria. In J. D. Wehr, R. G. Sheath, & J. P. Kociolek (Eds.), Freshwater Algae of North America: Ecology and Classification (2nd ed., pp. 183-214). Waltham, MA: Elsevier.
- Komárek, J. (2013). Cyanoprokaryota-3. Teil/Part 3: Heterocytous Genera (J. R. Johansen, Ed.). In B. Büdel, G. Gärtner, L. Krienitz, & M. Schagerl (Eds.), Süßwasserflora von Mitteleuropa (Vol. 19/3, pp. 697-698). Heidelberg, Germany: Springer Spektrum.