Acute toxicity of diflubenzuron (DFB) to various life stages of the grass shrimp, Palaemonetes pugio

The effects of acute concentrations of DFB on the estuarine grass shrimp at the stages of embryos, larvae, postlarvae non-spawning adults and ovigerous females were studied. The larvae and postlarvae were most sensitive with respective 96 h LC50's of 1.44 and 1.62 ug per litre. Ovigerous female grass shrimps, and hence the embryos, were the most resistant with a mean LC50 of 6985 ug per litre. These results have limited significance because the ovigerous females do not moult until 1 to 2 days after the eggs hatch and, therefore, acute toxicity tests would be misleading. The toxicity of most pollutants, and DFB in particular, to crustaceans is moult-dependent.