Effects of heavy metals in the brine shrimp, Artemia salina L.

Abstract

The effects of various salts of lead, iron, zinc and copper on the different stages of Artemia Salina L are studied. This includes effects of different concentrations of the four metals on hatching and larval growth. Various degrees of inhibition in the hatching of exposed eggs are observed with all salts. Inhibition of growth is also generally shown in varying degrees on exposure of newly-hatched larvae to low concentrations of the four metals, this inhibition varying not only with the different metals, but also in some instances, with the different salts of the same metal, and with the concentration. The main part of the work is concerned with the toxicity of the metals to 2-week old adults, and the difference in toxicity between (a) control animals, and (b) animals "acclimated" in low concentrations of the metal salts prior to exposure to medium and high concentrations. The "acclimation-effect" is not specific and pre-treatment with a particular metal increases the animals' tolerance not only to higher concentrations of the same metal, but also, in several instances, to other metals to which the animals were not previously exposed. The increase in tolerance is observed best in the medium concentration range - at relatively high concentrations, the differences between treated and control animals becomes insignificant. It is suggested that this required tolerance or acclimation-effect may be occurring because of the binding of the heavy metal ions to negative changes on the carapace, causing the formation of an effective barrier which can then repulse the heavy metal ions when the animal is exposed to a high concentration, resulting in an increased tolerance to this. This barrier would be incapable of forming quickly enough when the animal is subjected to a relatively high concentration without having undergone a period of acclimation at relatively low concentrations. In studying the effect of anions, the only organic anion used (acetate) decreased the acclimating effect of the cation. This is tentatively interpreted as being due to the ease by which the heavy metal was taken in rather than forming a protective coat. This contrasts with the effect of the other anions (sulphate, chloride and nitrate). Suggestions for future work include the pinpointing of the location of the metal ions after the pre-treatment period, comparison of the metal content of the tissues of acclimated and unacclimated animals during the test period and studies on the possible reversal of the acclimation effect through an interruption of the pre-treatment period before tolerance tests.