The action of heavy metals on the gametes of the marine mussel, Mytilus edulis (L.)—III. The effect of applied copper and zinc on sperm motilityin relation to ultrastructural damage and intracellular metal localisation

Treatment of Mytilus edulis sperm with external concentrations of copper or zinc (0-1-3-3mM) causes a decrease in motility in which zinc is more inhibitory than copper. Zinc also appeared to cause more extensive mitochondrial damage, as revealed by transmission electron microscopy, than did treatment with copper. The relationship between sperm motility and respiration in the presence of the various heavy metal concentrations used indicates that the depression of sperm motility can be explained largely on the basis of respiratory inhibition. However, zinc produces a less pronounced effect on sperm motility than on r respiration.X-ray microanalysis of thick sections of fixed treated sperm showed that copper accumulation occurs in the acrosomes, mitochondria and nuclei, whereas zinc is found in the acrosomes and in mitochondrial granules in association with calcium and phosphorus. No evidence was obtained for zinc accumulation in the nuclei. Treatment with either copper or zinc resulted in considerable reductions of bound calcium and phosphorus in both the acrosomes and mitochondria. It is suggested that the heavy metal ions cause an increase in the permeability of the organelle membranes to calcium and phosphorus.It is concluded that the less marked effect of zinc on sperm motility as compared to respiration may be due to an increase in the cytosolic free calcium concentration which, in turn, may stimulate the flagellar contractile apparatus.