Protracted toxic effects caused by saline extracts of Aphanizomenon flos-aquae (Cyanophyceae/Cyanobacteria)

Abstract

Secondary metabolites of toxic nature in cyanophytes exhibit a broad spectrum of effects versus other biota. Intoxications noticed during mouse bioassays, with death occurring 16–24 h or later after intraperitoneal injection, are designated protracted toxic effects. Nuisance blooms with protracted toxic strains of Aphanizomenon flos-aquae are frequent in Norway. Acute toxicity testing of 23 populations of A. flos-aquae from 12 localities of inland waters in South Norway, resulted in demonstration of 13 cases with protracted toxic response in the test animals. Material from waterblooms of non toxic and protracted toxic nature have been used in qualitative investigations with the objective to study the histopathological effects of the protracted toxic principle. Acute toxicity testing was performed (standard mouse bioassay) on saline extracts of the lyophilized cyanophyte material. Symptoms and death time were observed, and microscopical examination of organ damage was performed (using optical- and electron microscopy). Tissue samples of liver and lungs were used for detailed studies. Liver injury consisted of degenerative/necrotizing hepatocytic damage, with distinguishable cytoplasmic and nuclear vacuolation. The pulmonary lesions were characterized by thickening and hypercellularity of interalveolar septa, together with necrosis of bronchiolar and alveolar epithelium. Control animals injected with physiological saline did not exhibit histopathological damage in any organs.