Combination Toxicity of Glyphosate and Inorganic Mercury (II) Chloride on Developmental Damages to Zebrafish Embryos**
The purpose of this study was to examine the combination toxicity of glyphosate –mercury to and their uptake rates by Danio rerio (zebrafish) embryos. Glyphosate, the active ingredient in the most popular herbicide -Roundup, may present potential toxicity to the environment because of its heavy use. At the same time, the presence of glyphosate in the environment may increase the toxicity of other toxicants such as mercury. It was found that concentration map of mercury across the United States, overlaps with usage maps of glyphosate for some areas. The combination toxicity between glyphosate and inorganic mercury may present more concerns than individuals alone. This study was conducted by comparing developmental behaviors of zebrafish embryos under control (zero of glyphosate and of inorganic mercury), 2.5 ppm of glyphosate, 16 and 32 ppb of mercury (II) chloride, and combination of 2.5 ppm of glyphosate with mercury (II) chloride at 16 ppb and 32 ppb, respectively. The incubation time of the embryos was 7 days. The toxicity was evaluated by counting ratio of morphological deformity, and ratio of death of zebrafish embryos. The levels of glyphosate and mercury uptakes will be assessed by spectrometric methods. Our preliminary results show differences of zebrafish embryos behaviors among four experiments at different concentrations of glyphosate and inorganic mercury.