Fig. 5. 24h median lethal concentrations (LC₅₀) (+95% CI) for 3 and 7 days postfertilization zebrafish larvae exposed to MS222 in normoxic fresh water, normoxic 50% physiological saline and hyperoxic fresh water. Dashed lines indicate approximate median survival times (ET₅₀) for suppression of ventilatory movements. The asterisk indicates a significant difference in median survival time compared with normoxic fresh water within an age class. Numbers in parentheses indicate the number of trials.