The Toxic Action of Heavy Metal Salts on the Three-Spined Stickleback ( Gastrosteus Aculeatus )

Abstract

The observations and conclusions of Carpenter (1927, 1930) regarding the toxic effect of heavy metal salts on the minnow (Leuciscus phoxinus) are shown to apply equally well to the three-spined stickleback (Gastrosteus aculeatus). It is shown that in the case of heavy metal salts the toxic effect of hypertonic solutions is due chiefly to the metallic cation, the toxicity of the anion being relatively small, while in the case of hypotonic solutions the toxicity is due entirely or almost entirely to the cation. Nevertheless, in equimolar concentrations, different salts of the same metal do not have equal or approximately equal toxicity. At the same molar concentration the sulphates of heavy metals are much less toxic than the nitrates or chlorides. This is not due to difference of pH. This difference in toxicity is shown to be closely related to difference in relative electrical conductivity; the toxicity of nitrate, chloride and sulphate is determined, not by the normality alone, but by the product of the normality and conductance ratio. It is concluded that the factors responsible for the lower electrical conductivity of the sulphate also lower the chemical activity of the sulphate so that the toxicity falls in proportion to the conductivity.