Watercress and Water Quality: The Effect of Phenethyl Isothiocyanate on the Mating Behaviour ofGammarus pulex

Abstract

Watercress releases phenethyl isothiocyanate (PEITC) upon wounding as a defence against herbivores. PEITC levels released from watercress farms are elevated due to cropping, washing, and processing and are thought to lead to adverse effects onGammarus pulexin chalk streams. This study elucidates the sublethal effect of PEITC on reproductive behaviour ofG. pulex, employingex situtests to investigate the disruption of precopular pairing under conditions simulatingin situexposure. Mean time to separation of precopular pairs was 89 ± 6 minutes for watercress wash water (1 g watercress per litre water) and 81 ± 15 minutes for pure PEITC (1 μL/L). Re-exposure to watercress wash water to simulate the pulsed operation at a watercress farm did not alter behavioural response. The repeated interruption of reproductive behaviour underin situconditions would impair long-term reproductive success and could explain in part low abundance ofG. pulexdownstream of watercress farms.