The Reactions of Pygosteus Pungitius L. to Toxic Solutions

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Abstract
An apparatus is described in which small fish (Pygosteus pungitius L.) are confined in a horizontal glass tube, half of which is filled with flowing tap water and half with flowing solution. Solution and water are very sharply differentiated, so that the concentration difference the fish encounter is known. The directions of flow can be rapidly reversed in order to check the result. The movements of the fish are recorded for 7-120 min., according to the degree of toxicity of the substance tested. A negative reaction is shown towards 1% ethyl alcohol, 1/10,000-1/5000 chloroform and 0.1-0.4% formalin (% HCHO). High concentrations of these substances may stupefy the fish so rapidly that a pseudo-positive reaction appears. A sharp negative reaction is displayed towards 0.003-0.001N mercuric chloride; at 0.0003 the reaction is delayed, at 0.0001 is indefinite, and at 0.00004N solution, though of comparatively high toxicity, does not appear to be detected. Zinc sulphate appears to be detected and avoided at concentrations at least as low as 0.0003N. This concentration is of comparatively low toxicity and may be exceeded in streams polluted by effluents from zinc mines. Copper sulphate is only detected and avoided at extremely high concentrations (0.1N). At 0.04N the reaction is vague, and at 0.01-0.001N the fish swim into the solution where they become stupefied and lie motionless, so that the reaction appears positive. Copper salts appear to impair or destroy the stickleback’s ability to distinguish other toxic substances.
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