Phylum: Cyanobacteria – blue-green algae
British distribution (genus): Evidently widespread, freshwater and marine.
World distribution (genus): Cosmopolitan?
|Calothrix trichomes: material in culture, named as C. viguieri|
Calothrix is characterised by its tapering trichomes with terminal (and sometimes intercalary) heterocysts [or 'heterocytes']. The lower part of the trichome is usually enclosed in a firm, colourless or yellow-brown sheath (not clearly visible in the cultured material shown here). The genus merges into the closely related genus, Dichothrix, distinguished by usually multiple trichomes within a single sheath and a greater tendency to 'false-branching'.
There are a number of species, some freshwater, others marine, forming thin, mucilaginous films or crusts on rocks and aquatic plants, including seaweeds. Calothrix also occus as a lichen photobiont, when it may become more or less unicellular or form short chains of globose cells rather than forming trichomes.
| |Photobiont in the maritime lichen, Lichina confinis. This is either Calothrix or possibly the very closely related genus Dichothrix. Material from maritime rocks, Arbroath, Angus, April 2002. | |
© A.J. Silverside|
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