Effects of in vitro exposure of mercury on sperm quality and fertility of tropical fish Cyprinus carpio L.

Abstract

Mercury is a widespread aquatic pollutant that adversely affects the reproductive system of male fish. Although the effects of mercuric chloride (HgCl2) on the testicular structure, the sperm count and altered sperm morphology of fish have been investigated, the effects on sperm quality and fertilization are unknown. Therefore, the aim of this study was to investigate the effects of HgCl2 exposure in different concentrations (0; 0.5; 1; 2.5; 5 ppm) on sperm parameters and fertility of male Cyprinus carpio. Sperm quality parameters, including mass and individual time of sperm motility (s), and viability (%) were measured using digital inverted microscopy. The fertilization (%) was measured by counting the number of fertilized eggs. Integrity or DNA fragmentation (%) was measured by Acridine orange test (AOT) using fluorescence microscopy. The change of sperm membrane surface was examined using scanning electron microscopy (SEM). The results showed that the in vitro exposure of mercury could significantly decrease some parameters of fish sperm qualities, i.e. decreased the time for mass and individual motility, viability, DNA fragmentation, and fertilization ability (P < 0.05) and significantly increase the malondialdehyde levels of sperm (P < 0.05). In addition, Hg exposure altered the morphological structure of the sperm head and interfered with the development of embryos in fish eggs.