Reduced metabolic rate and increased heart beat as early signs of sub lethal Copper toxicity in developing Zebrafish

The current study looks at acute and sub-lethal Copper toxicity on developing zebrafish embryos up to 96 hours post fertilisation (PSF). We allocated four-hour PSF zebrafish embryos in four groups with duplicates, and 500 mg, 50 mg, and 0.05 mg l−1 and a control group for 96 hours PSF. All fish exposed to 500 mg l−1 copper died within the first 6 hours PSF. Significant sub-lethal copper toxic effects on developing Zebrafish were manifested in the 0.05 and the 50 mg groups, by increased heartbeat rate within the first 25 hours PSF in the 0.05 and 50 mg group. The sub-lethal toxic effect was also manifested in the metabolism of developing embryos, with a reduced rate of utilisation of yolk and lower growth rate and anatomical malformations within the first 25 hours in the 50 mg group and after 50 hours PSF in both the 0.05 and 50 mg group. The results indicate that reduced metabolic rate and increased heartbeat rate are potential early signs of sub-lethal Cu toxicity in developing Zebrafish well before other developmental defects are visually evident.