Non-lethal presence of predators modifies morphology and movement rates in Euplotes
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Many species are able to modify aspects of their behaviour and morphology in the presence of predators. The aim of this study was to investigate the relationship between the expression of morphological and behavioural defences according to the framework proposed by DeWitt et al (1999). Experiments were carried out using hypotrich ciliates of the genus Euplotes as prey and turbellarians of the genus Stenostomum as predators. The smaller species Euplotes octocarinatus showed a greater proportional increase in width, a reduction in foraging movement rates and an increase in maximum movement rates following exposure to predator cues. The larger Euplotes aediculatus induced lesser changes in width, similar reductions in movement during foraging and no change in maximum speed following predator exposure. These results provide evidence of a cospecialised relationship between morphological and behavioural defences. Despite substantial differences in the absence of predators, movement rates and lateral body width were similar in both species following predator exposure. The observed changes may be considered adaptive, gape limited flatworm predators are unable to ingest large Euplotes and a reduction in movement rates during foraging reduces predator encounter rates, while an increase in maximal movement rates increases chances of predator evasion.
KeywordsBehaviour Inducible defences Predator–prey Swimming speed Stenostomum
We wish to thank John Taylor for the use of microscopic equipment (funded by CFI) and Maarten Voordouw for his insightful comments on earlier versions of this manuscript. This work was funded by an NSERC Discovery grant awarded to Bradley R. Anholt and the Canada Research Chairs programme.
- Altwegg, R., M. Eng, S. Caspersen & B. R. Anholt, 2006. Functional response and prey defence level in an experimental predator-prey system. Evolutionary Ecology Research 8: 115–128.Google Scholar
- Anholt, B. R., E. Werner & D. K. Skelly, 2000. Effect of food and predators on the activity of four larval ranid frogs. Ecology 81: 3509–3521.Google Scholar
- Kuhlmann, H. W., 1994. Escape response of Euplotes-Octocarinatus to turbellarian predators. Archiv Fur Protistenkunde 144: 163–171.Google Scholar
- Lima, S. L., 1998. Stress and decision making under the risk of predation: Recent developments from behavioral, reproductive, and ecological perspectives. Stress and Behavior: 215–290.Google Scholar
- Morin, P., 1999. Productivity, intraguild predation, and population dynamics in experimental food webs. Ecology 80: 752–760.Google Scholar
- Pardi, L. & F. Papi, 1967. Kinetic and tactic responses. In Waterman, T. H. (ed.), The Physiology of Crustacea. Academic Press, New York and London: 365–399.Google Scholar
- Tillmann, U. & W. Lampert, 1984. Competitive ability of differently sized daphnia species—an experimental test. Journal of Freshwater Ecology 2: 311–323.Google Scholar
- Tollrian, R. & C. D. Harvell, 1999. The Ecology and Evolution of Inducible Defenses. Princeton University Press, Princeton.Google Scholar