Histopathological and biological studies of the effect of cadmium on Rhinella arenarum gonads

This study was to determine the lethal dose 50 (LD₅₀) of CdCl₂ in adult Rhinella arenarum and analyzed the effect of two sublethal doses (0.5 and 5 mg/kg) of the xenobiotic in gonads. The 48 h LD₅₀ were 50.0 and 49.8 mg/kg for males and females respectively. Alterations in the ovary were evidenced by nuclear pleomorphism and cytoplasmic vacuolization of the oocytes at the early stages of development with the highest dose and an increase in the population of atretic oocytes. In the interstitial tissue we noticed congestion, edema and fibroblast proliferation. The nuclear maturation of the oocytes was affected by the xenobiotic in a dose- and time-dependent manner. In males, treatment with 5 mg/kg of cadmium (Cd) caused a decrease in the concentration, viability and straight progressive motility of sperm while there was an increase in immotile sperm. Testis histopathology revealed dilated seminiferous tubules, disappearance of cysts, tissue disorganization and leukocyte infiltration. Numerous germ cells showed hydropic tumefaction or signs of focal necrosis. The Cd content in animals intoxicated gonads with the highest sublethal dose was significantly higher than in the control. Results indicate that R. arenarum gonads are target for the xenobiotic, compromising the formation of gametes competent for fertilization, the effective CdCl₂ dose being 5 mg/kg.