typical filament with 3 heterocytes
Aphanizomenon ovalisporum (Cyanobacteria, Nostocales) was the first N2-fixing filamentous cyanobacterium that ever bloomed in Lake Kinneret. It happened in 1994 when this species formed an unprecedented autumn bloom. Since then Cylindrospermosis cuspis, another N2 fixer, invaded the lake and now dominates the summer-fall phytoplankton assemblages. A. ovalisporum produces the toxin cylindrospermopsin, which makes it an undesirable species in this important source of drinking water. Aphanizomenon ovalisporum is abundant during summer and fall, being evenly distributed with depth throughout the epilimnion. The filaments are 2 – 5 µm thick and 20 – 500 µm long. Heterocytes (seen as 3 distinct oval cells dispersed along the filament) appear when N-deficient conditions prevail. Akinete formation is induced by P-deficiency. The akinetes (not seen here) are much larger than regular cells and can be mid-filament or terminal, at times a few in a single filament, sometimes several in a row. This specimen was sampled from shallow water near the Kinneret Limnological Laboratory in June 2006. This image was taken by Alla Alster using an Olympus BX50 Microscope equipped with DIC optics. The copyright holders of this image are Alla Alster & Tamar Zohary and the image is used by micro*scope with agreement of the authors.
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From the collection
Lake Kinneret planktonic life forms
No description of Aphanizomenon ovalisporum available.
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