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International Journal of Zoology
Volume 2011, Article ID 328749, 9 pages
Research Article

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

Centre for Environmental Sciences, Faculty of Engineering and the Environment, University of Southampton, Highfield, Southampton SO17 1BJ, UK

Received 23 December 2010; Accepted 8 March 2011

Academic Editor: Michelle Bloor

Copyright © 2011 Melanie J. Dixon and Peter J. Shaw. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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 on Gammarus pulex in chalk streams. This study elucidates the sublethal effect of PEITC on reproductive behaviour of G. pulex, employing ex situ tests to investigate the disruption of precopular pairing under conditions simulating in situ exposure. 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 under in situ conditions would impair long-term reproductive success and could explain in part low abundance of G. pulex downstream of watercress farms.