Toxicity of chlorpyrifos to the early life history stages of eastern rainbowfish Melanotaenia splendida splendida (Peters 1866) in tropical Australia.

Abstract

Various life history stages of the eastern rainbowfish Melanotaenia splendida splendida were exposed to the organophosphorus insecticide chlorpyrifos at different temperatures and under different exposure regimes. Chlorpyrifos was found to be highly toxic to all stages of M. s. splendida and became significantly more toxic to embryonic and larval fish as the temperature of the exposure increased. The toxicity of chlorpyrifos was found to be different for each of the various life history stages tested, with the LC50 values increasing from 0.02 mg chlorpyrifos L(-1), for eggs and sperm exposed prior to fertilization, to 2.02 mg chlorpyrifos L(-1), for eggs exposed after fertilization and hardening of the chorion. Sublethal early life stage (ELS) tests revealed that larval length and otolith perimeter were the most sensitive indicators of stress, with significant differences from the controls at chlorpyrifos concentrations as low as 0.006 mg L(-1).