The effect of metals and cyanide on fertilization in rainbow trout ( Salmo gairdneri)

Abstract

This paper reports a study testing the effects of several heavy metals and cyanide on fertilization in rainbow trout. Two tests were carried out. 1. (1) The gametes were exposed independently for 40 min to a test chemical added into diluents. The ovum diluent (ID) was a NaCl solution (osmotic pressure: 250 mOsm kg −1), pH 9.0, Tris 20 mM, glycine 50 mM. The spermatozoa were diluted at 10 −1 and 10 −2 and the same diluent with K + added; they were immobile in this diluent (CD). Insemination was carried out after the gametes had been washed. 2. (2) Ova and spermatozoa were mixed together in ID containing one of the chemicals to be tested (insemination test). In test 1 in which gametes were exposed over an extended time, the chemicals were only very slightly toxic to ova compared to sperm. Iron became toxic for ova at a concentration of 0.073 mg 1 −1 and the toxic thresholds of the other products were higher than 1 mg 1 −1. The chemicals had a more marked toxic effect on sperm diluted at 10 −2 in the following decreasing order (in mg 1 −1): chromium 0.005, iron 0.005, cyanide 1, zinc 20. Insemination sometimes revealed lower thresholds of toxicity: chromium 0.005, iron 0.08, cyanide 0.001, mercury > 1. Copper had a favorable effect on fertilization. The tests, and particularly the insemination test, could be used to monitor the toxic effect of chemical on a stage of the life-cycle of fish which has been little studied up to now.