Effect of Inorganic Mercury on Semen Quality, Embryo and Larval Development of Bocachico Prochilodus magdalenae

Abstract

The study aimed to evaluate the effect of inorganic mercury (iHg) on the sperm quality, embryos, and larvae of Prochilodus magdalenae. Two experiments were carried out. In experiment 1, semen was activated with contaminated water at different iHg concentrations (0.0, 25, 50, 100 µg/L) and sperm kinetics were analyzed with a computer-assisted semen analysis (CASA) system. In the second trial, 2 g of oocytes were fertilized with 50 µL of milt, activated with contaminated water at different iHg concentrations (0.0, 25, 50, 100 µg/L), and maintained that way during the first hour of incubation. Samples were taken every 3–4 h until hatching to identify embryo deformations. Fertilization and hatching rates were estimated. The survival of newly hatched larvae (1 day) and larvae eight days post-hatching (dph) was also assessed. The results show that the quality parameters of semen treated with contaminated water at different iHg concentrations (25, 50, 100 µg/L) were altered and showed significant differences (p < 0.05) from the control group (0 µg/L). Total motility decreased (9.8–13.2%) and the amount of immotile sperm increased (3-fold) relative to values in the control group. A significant increase in oocyte diameter and a decrease in fertilization and hatching rates were observed with the higher iHg concentrations (50–100 µg/L). Embryo deformations (>40%) such as scoliosis, lordosis, and microcephaly were observed, as well as premature hatchings. The larval survival at 1 dph was reduced between 25% (25 µg/L) and 97.2% (100 µg/L) relative to that in the control group. The results suggest that bocachico semen, embryos, and larvae are sensitive to contamination with iHg from 25 µg/L.