LAUSR

ABSTRACT Environmental pollution is a threat to circadian rhythms of behaviour and physiology of organisms. The daily rhythm of swimming activity in zebrafish Danio rerio was studied to evaluate the toxicity of water from Lerma River, in Mexico, as it passed through the city of Salamanca, Guanajuato. Swimming activity along 3 days of acute exposure to polluted water, and then, the activity of the enzyme acetylcholinesterase and the oxidative stress in homogenized tissue was tested. Exposure to polluted water drastically reduces magnitude and alters the daily pattern of swimming activity. Cosinor analysis shows effect on mesor and robustness of rhythms,  Tissue analysis showed a negative effect on AChE or an increase on oxidative stress. The analysis of water ions Al, P, F−, PO4 3-, SO4 2- in concentrations above the established in the official references. We discuss that daily swimming activity in zebra fish is useful to test water quality in polluted environments.