title: Swimming with predators and pesticides: how environmental stressors affect the thermal physiology of tadpoles.
abstract: To forecast biological responses to changing environments, we need to understand how a species's physiology varies through space and time and assess how changes in physiological function due to environmental changes may interact with phenotypic changes caused by other types of environmental variation. Amphibian larvae are well known for expressing environmentally induced phenotypes, but relatively little is known about how these responses might interact with changing temperatures and their thermal physiology. To address this question, we studied the thermal physiology of grey treefrog tadpoles (Hyla versicolor) by determining whether exposures to predator cues and an herbicide (Roundup) can alter their critical maximum temperature (CTmax) and their swimming speed across a range of temperatures, which provides estimates of optimal temperature (Topt) for swimming speed and the shape of the thermal performance curve (TPC). We discovered that predator cues induced a 0.4°C higher CTmax value, whereas the herbicide had no effect. Tadpoles exposed to predator cues or the herbicide swam faster than control tadpoles and the increase in burst speed was higher near Topt. In regard to the shape of the TPC, exposure to predator cues increased Topt by 1.5°C, while exposure to the herbicide marginally lowered Topt by 0.4°C. Combining predator cues and the herbicide produced an intermediate Topt that was 0.5°C higher than the control. To our knowledge this is the first study to demonstrate a predator altering the thermal physiology of amphibian larvae (prey) by increasing CTmax, increasing the optimum temperature, and producing changes in the thermal performance curves. Furthermore, these plastic responses of CTmax and TPC to different inducing environments should be considered when forecasting biological responses to global warming.
authors.affiliation: Department of Evolutionary Ecology, Doñana Biological Station - Spanish Council for Scientific Research, Sevilla, Spain.
authors.forename: Marco
authors.initials: M
authors.lastname: Katzenberger
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America.
authors.forename: John
authors.initials: J
authors.lastname: Hammond
authors.affiliation: Department of Evolutionary Ecology, Doñana Biological Station - Spanish Council for Scientific Research, Sevilla, Spain.
authors.forename: Helder
authors.initials: H
authors.lastname: Duarte
authors.affiliation: Department of Evolutionary Ecology, Doñana Biological Station - Spanish Council for Scientific Research, Sevilla, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Tejedo
authors.affiliation: Department of Animal Sciences, Federal Rural University of the Semiarid Region, Mossoró, Rio Grande do Norte, Brazil.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Calabuig
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
authors.forename: Rick A
authors.initials: RA
authors.lastname: Relyea
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001001:Anura / Q000502:physiology*; D004777:Environment; D020387:Food Chain; D005998:Glycine / Q000031:analogs & derivatives / Q000633:toxicity; D006540:Herbicides / Q000633:toxicity*; D007814:Larva / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D013312:Stress, Physiological / Q000187:drug effects / Q000502:physiology*; D013550:Swimming / Q000502:physiology*; D013696:Temperature; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate