Cell dimensions and taxonomy ofAnabaena variabilis Kütz. emend. (Cyanophycea)

Abstract

MaterialThe present study is based on material from a lagoon with brackish water situated on a narrow peninsula, Knudshoved (the island of Sjmlland, Denmark). This lagoon, which is a recipient of rain water and to which sea water penetrates at high water, has a depth of 0.15-0.20 metres. The bottom is completely covered with a dark bluishgreen film of algae below which there is a layer of black mud.The film consists almost exclusively of. the bluish-green alga Anabaena variabilis Ktitz. with a sprinkling of green algae such as Enteromorpha sp., Ulothrix sp., Cladophora sp., and bluish-green algae such as Nodularia spumigena Mertens, N. Harveyana (Thwait.) Thuret, Oscillat~ria brevis (Ktitz.) Gore., Phorrnidi~,m mucosum Gardner, Merismopedia tenuissirna Lemm., and M. punctata Meyen.The brackish nature of the lagoon appears also from the presence of typical brackish-water diatoms as Campylodiscus clypeus Ehrbg. and C. hibernicus Ehrbg.In the mud there is vigorous bacterial activity with development of gas of an odour which indicates the presence of hydrogen sulphide -deriving from the reduction of the sulphate which enters the lagoon with the sea water by Desulphovibrio desuLfuricans, the presence of which has been demonstrated. Morphology and cell dimensionsTrichomes are bluish-green, bent, and more or less constricted at cross walls. With the exception of HANSGIRG [15] and LINDSTEDT I20], who found the trichomes to be considerably constricted at the cross walls, authors generally describe the trichomes as slightly constricted at cross walls. The cells are short, barrel-shaped, or almost isodiametric. The end cells are truncated cones, but typical end cells do not occur generally in the material -probably they break off easily (see Fig. 1). The heterocysts are spherical or ovoid. The akinetes are smooth, ovoid, spherical, or compressed spherical with truncated ends, numerous (in the present material up to 14) in catenate series, remote from the heterocysts.

Efficacy of molecular DNA methods for confirming species identifications on morphologically variable populations of toxin-producingAnabaena(Nostocales)

“…Adequately describing cell dimensions and colonial attributes to correctly diagnose species is challenging (Fjerdingstad 1969); distinguishing among closely related species becomes even more difficult when the diacritical features overlap, and the taxonomic keys provide differing descriptions (e.g., John et al 2002vs. Desikachary 1959.…”

Taxonomy of blue-green algae-problems and prospects

“…We have become accustomed to studying these algae under natural condition (i.e. see FJERDINGSTAD [3,4,5,6]). But it is now essential to study the extent of variation in these characteristics in any taxon under different milieh i.e.…”