Lethal and sublethal costs of autotomy and predator presence in damselfly larvae |
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Authors: | Robby Stoks Marjan De Block Hans Van Gossum Famke Valck Kris Lauwers Ron Verhagen Erik Matthysen Luc De Bruyn |
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Institution: | (1) Evolutionary Biology Group, University of Antwerp (RUCA), Groenenborgerlaan 171, B-2020 Antwerp, Belgium e-mail: stoks@ruca.ua.ac.be, Fax: +32-3-2180474, BE;(2) Laboratory for Animal Ecology, University of Antwerp (UIA), Universiteitsplein 1, B-2610 Wilrijk, Belgium, BE |
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Abstract: | We studied the costs of lamellae autotomy with respect to growth and survival of Lestes sponsa damselfly larvae in field experiments. We manipulated predation risk by Aeshna cyanea dragonfly larvae and lamellae status of L. sponsa larvae in field enclosures and compared differences in numbers, size and mass of survivors among treatments. In the absence
of a free-ranging A. cyanea larva, about 29% of the L. sponsa larvae died. This was probably due to cannibalism. The presence of a free-ranging A. cyanea reduced larval survival by 68% compared to treatments in which it was absent or not permitted to forage on L. sponsa damselflies. Across all predator treatments, lamellae autotomy reduced survival by about 20%. The mean head width and mass
of survivors was lower in the enclosures with a free-ranging A. cyanea compared to the other two predator treatments. This suggested that larvae grew less in the presence of a free-ranging predator,
indicating that increased antipredator behaviours were more important in shaping growth responses than reduced population
density. Mass, but not head width, of survivors was also reduced after autotomy. The fitness consequences of these effects
for the adults may be pronounced. In general, these field data strongly suggest that lamellae autotomy affects population
regulation of damselflies.
Received: 1 February 1999 / Accepted: 22 March 1999 |
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Keywords: | Autotomy Growth Lestes sponsa Predation Survival |
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