ABSTRACT: Investigations of the effects of grazing by 3 species of ciliates -- Pseudomicrothorax dubius Peck, Nassula citrea Kahl and Furgasonia blochmanni Faure-Fremiet -- on mats of Phormidium autumnale (Agardh) Gomont showed that the cyanobacterium was capable of surviving very strong grazer pressure, thanks to both an extracellular polysaccharide (EPS) layer and behavioral defense. In the presence of ciliates, cyanobacteria trichomes were confined to a protective layer of extracellular material enclosing the mat. Trichomes attacked by a ciliate usually escaped by retreating within the EPS layer. The effectiveness of this kind of defense was reflected in dramatic changes in the condition of the ciliates: within 30 h of the start of the experiments a significant fraction was starved because they were unable to reach trichomes hidden within the shielding EPS layer.

KEY WORDS: Ciliates · Cyanobacteria · Extracellular polysaccharides · Defense

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Published in AME Vol. 23, No. 3 (2001) on February 28
ISSN: 0948-3055. Copyright © Inter-Research, Oldendorf/Luhe, 2001