Behavioural responses of two cladocerans and two copepods exposed to fish kairomones

Abstract

In natural predator–prey interactions, chemical communication is one of the most advantageous strategies for prey organisms because they can anticipate possible harm by means of phenotypic changes. This study compares the changes in the behaviour of four freshwater zooplankton species in the presence and absence of infochemicals from the same predator. The studied organisms are two copepods and two cladocerans living in highly variable freshwater environments. The analysis is focused on two predator defensive behaviours: a pre-encounter and a post-encounter response. First, we analysed the diel vertical migration (DVM) of the organisms inside 150 cm long transparent plastic tubes. Second, we used a novel hydraulic apparatus to quantify their ability to escape from a potential predator. The results revealed that the species have different behavioural patterns in the absence of infochemical. The differences were mainly in the way DVM developed and reflect their life histories and adaptive strategies relative to their natural environment. When faced with kairomones, the escape ability of the organisms was enhanced in all cases and DVM changed, although not always in agreement with the expected patterns. The interaction between each species and the multiple environmental components is discussed.

Keywords:

• Behaviour
• Chemical communication
• Cladocera
• Copepoda

Acknowledgements

We are grateful to Leonardo Paggi and Oscar Mendoza for their technical assistance. This research was supported with grants from the Universidad Nacional del Litoral, Santa Fe, Argentina (Project CAI+D 2009 N° PI 69-351). We also appreciate constructive comments on this study by anonymous reviewers.