Effect of copper exposure on reproductive ability in the bank vole (Myodes glareolus)

The amount of copper in natural ecosystems is steadily increasing, due to human activities. It accumulates in plants, posing a threat to herbivores. In polluted areas the population density of small rodents is observed to be lower. The decline in rodent numbers may be caused by increased mortality or diminished fertility. This study examined the effect of copper on the reproductive activity of the bank vole (Myodes glareolus), a small rodent which during foraging often wanders into fields where it might be exposed to pollution. The animals were treated with solutions of 0, 150 or 600 ppm Cu. After 12 weeks of exposure the quality and quantity of the male's sperm was tested. To assess morphological development we compared the experimental groups for body weight, the weight of the male's testes and accessory sex glands, the female's uterus, and the number of matured ovary follicles in tested females. At both doses, copper administration led to lower sperm count and caused sperm head anomalies. The higher dose compromised sperm tail membrane integrity, viability and motility. No effect of copper on morphological development was observed in males, and only the lower dose increased testes weight. In females the higher dose had a negative effect on morphological development, and the lower dose increased uterus weight. No effect of copper on ovarian follicle number was found. For the first time, the morphology of the most typical ovarian follicles of the bank vole is presented.