Effects of in vitro exposure to mercury on male gonads and sperm structure of the tropical fish tuvira Gymnotus carapo (L.)

This study investigated the progressive effects of HgCl2 in the testis and sperm of the tropical fish tuvira Gymnotus carapo L. exposed to increasing Hg concentrations (5-30 mu m) and increasing exposure times (24-96h). Histopathology and metal concentrations in the testis were observed. Hg concentrations in the testis reached 5.1 and 5.2 mu gg(-1) in fish exposed to 20 and 30 mu m of Hg, respectively. Hg effects on testicular tissue were observed even at low Hg concentrations, with no alterations in gonadosomatic index. However, the quantitative analysis of the induced alterations (lesion index) demonstrated that the Hg effects in testis became more severe after exposure to higher concentrations (20 and 30 mu m) and during longer exposure (72 and 96h), probably leading to partial or total loss of the organ function. Hg exposure (20 mu m) also affected sperm count and altered sperm morphology. This study showed that HgCl2 caused progressive damage to testicular tissue, reduced sperm count and altered sperm morphology. These results are important in establishing a direct correlation between Hg accumulation and severity of lesions.