Consequences of compensatory growth in an amphibian

Authors


  • Editor: Mark-Oliver Rödel

Katie L. Hector, Department of Zoology, 340 Great King St, University of Otago, Dunedin 9016, New Zealand. Tel: +64 03 479 5046; Fax: +64 03 479 7584 Email: katiehector1@gmail.com

Abstract

Compensatory growth, or catch-up growth, occurs when an organism grows faster than the optimal rate after a period of growth restriction. The evolved optimal growth rate maximizes an animal's fitness potential while preserving tissue quality. Rapid compensatory growth allows the organism to achieve an adult size closer to that of an unrestricted conspecific. However, this accelerated growth may come at the cost of impaired fitness later in life due to accumulated cellular damage. Amphibians are an interesting, yet neglected, group in which to observe the effects of compensatory growth because of their flexible life history and the importance of large size for reproductive fitness. We investigated the effects of early nutritional restriction on the growth, morphology and three fitness-related behavioural traits of brown tree frog tadpoles Litoria ewingii before and after metamorphosis. Tadpoles were fed reduced rations for two weeks, c. 35% of the control group's larval period, before being returned to the diet of the controls. The dietary treatment caused a significant difference in pre- and post-metamorphic survival between the groups. The tadpoles on the restricted diet exhibited faster weight gain upon refeeding and reached a final size significantly larger than the control tadpoles. However, the larval period of the restricted group was extended by c. 5 days, compared with the control group. Early nutritional restriction also negatively affected the pre-metamorphic fitness-related behavioural trait of swimming speed. The restricted group showed an unexpected advantage in both post-metamorphic fitness-related behavioural traits of feeding latency and hopping ability. These results contrast with previous work on compensatory growth in tadpoles because nutritional restriction affected the developmental rate and also resulted in ‘over-compensation’ of growth. Our experiment provides support for the prevalence of compensatory growth in diverse taxa and a unique observation of the post-metamorphic consequences in amphibians adapted to ephemeral environments.

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