Planktothrix: Morphological description

(from Anagnostidis & Komarek 1988, Komarek 2003)

Planktothrix grows in straight and single filaments due to cell division transversally to the longitudinal axis of a trichome. The cylindrical cells are only slightly constricted or unconstricted at the cross walls, up to 4mm in length, 3.5-10 µ wide. The cells are typically shorter than wide. The trichomes are slightly tapering at the ends, and may show a calyptra. The mucilagenous envelopes are lacking, fine visible sheaths are rarely observed.

The species have a planktic mode of life and the cells contain aerotopes (groups of gas vesicles) distributed obligatorily over the whole protoplast of the cells (in the light microscope gas vesicles appear as numerous black dots inside the cells). Further important features include the special type of motility of the filaments, i.e. gliding forward or backward along one another (Skulberg & Skulberg 1985). The trichomes are gathered in diffuse or tight clumps only during mass developments, after reaching a certain minimum concentration (Walsby et al. 1983).

Field populations of P. rubescens to date have never been found without microcystins, and where P. agardhii occurs, microcystins are also highly likely to be found.

According to the most current revision by Komarek (2003) the following species need to be considered:

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- examples from various freshwaters and water-body characteristics typically favouring the occurrence of these Planktothrix species (Kurmayer et al. 2004)

References

Anagnostidis, K. and Komarek, J. Modern approach to the classification system of cyanophytes,3-Oscillatoriales. Algological Studies. 1988; 50-53:327-472.

Komarek, J. Planktic oscillatorialean cyanoprokaryotes (short review according to combined phenotype and molecular aspects). Hydrobiologia. 2003; 502:367-382.

Kurmayer, R; Christiansen, G; Fastner, J, and Börner, T. Abundance of active and inactive microcystin genotypes in populations of the toxic cyanobacterium Planktothrix spp. Environmental Microbiology. 2004; 6:831-841.

Skulberg, O. M. and Skulberg, R. Planktic species of Oscillatoria (Cyanophyceae) from Norvay. Characterisation and classification. Algological Studies. 1985; 38/39:157-174.

Suda, S.; Watanabe, M. M.; Otsuka, S.; Mahakahant, A.; Yongmanitchai, W.; Nopartnaraporn, N.; Liu, Y., and Day, J. G. Taxonomic revision of water-bloom-forming species of oscillatorioid cyanobacteria. International Journal of Systematic and Evolutionary Microbiology. 2002; 52:1577-1595.

Walsby, A. E.; Utkilen, H. C., and Johnsen, I. J. Boyancy changes of a red coloured Oscillatoria agardhii in Lake Gjersjoen, Norway. Arch. Hydrobiol. 1983; 97:18-38.