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Relaxed circadian rhythm in zooplankton along a latitudinal gradient

Hansson, L-A. and Becares, E. and Fernández-Aláez, M. and Fernández-Aláez, C. and Kairesalo, T. and Miracle Rosa, M. and Romo, S. and Stephen, D. and Vakkilainen, K. and Bund Van de, W. and Van Donk, E. and Balayla, D. and Moss, B. (2007) Relaxed circadian rhythm in zooplankton along a latitudinal gradient. Oikos, 116, 585-591. ISSN 0030-1299. doi: 10.1111/j.2007.0030-1299.15754.x.

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To test whether aquatic invertebrates are able to adjust their diel migratory cycle to different day length and presence of predators, we performed standardized enclosure experiments in shallow lakes at four different latitudes from southern Spain, with strong night–day cycles, to Finland where daylight is almost continuous during summer. We show here that nearly continuous daylight at high latitudes causes a relaxation in diel migratory behaviour in zooplankton irrespective of predation risk. At lower latitudes, however, similar conditions lead to pronounced diel rhythms in migration. Hence, zooplankton may show local behavioural adaptations in their circadian rhythm. They are also able to make risk assessments as to whether diel migration is beneficial or not, manifested in a lack of diel migration at near constant daylight, irrespective of predator presence. Our results provide an additional explanation to previous knowledge regarding diel migrations among aquatic invertebrates by showing that both physical (light) and biological (predation) factors may affect the migratory behaviour.

Item Type:Article
Additional Information:doi: 10.1111/j.2007.0030-1299.15754.x
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:3736
Deposited On:16 Sep 2009 02:00
Last Modified:04 Sep 2014 10:06

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