When time turns the tide: the interactive effects of ammonium and warming during the larval stage on the resulting adult frogs.

backgroundTwo central elements of the global change are a rise in average temperatures and the contamination of natural habitats, among others, with agricultural fertilizers, which can stress living beings. Avoidance of these stressors is often impossible for animals confined in certain habitats, such as pond-dwelling tadpoles, which can indeed select less stressful microhabitats after metamorphosis. However, the stressors faced during the larval stage may have long-term repercussions.

methodsIn this work, we reared tadpoles in either heated or non-heated tanks, in each case either exposed or not to ammonium contamination. The resultant metamorphs were reared, released from such stressors, until adulthood, when their body size, body condition and locomotor performance were gauged.

resultsWhereas larvae reared in non-heated tanks responded to ammonium with a lower body size as adults, in accordance with previous experiments, the opposite was true for those reared in heated tanks. Body condition was greater in ammonium-exposed individuals, in which locomotor performance was reduced, as compared with non-ammonium-exposed conspecifics.

conclusionsGreater body size in adults in heated water as a response to ammonium could be a consequence of temperature mediating detoxifying metabolic routes of tadpoles. Better body condition and worse locomotor performance in ammonium-exposed individuals could reflect a prioritization of the storage of resources to the detriment of locomotion in ammonium-exposed individuals, or a limitation in the ability to optimize locomotion but not storage of resources.