Amphibian responses in experimental thermal gradients: Concepts and limits for inference

Navas, Carlos A.; Gouveia, Sidney F.; Solano-Iguarán, Jaiber J.; Vidal, Marcela A.; Bacigalupe, Leonardo D.

doi:10.1016/j.cbpb.2021.110576

Cited by 13 publications

(20 citation statements)

References 60 publications

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“…While this integrative behavioural approach has been used previously in lizards (Black and Tattersall 2017;Black et al 2021), it has now been shown to be viable in snakes. The study of thermoregulation in other systems could benefit from this approach, as appeals for integrative assessments have been mounting (e.g., Navas et al 2021). Including additional sources of thermoregulatory evidence, such as postural adjustments in relation to temperature (Du et al 2011;Du and Shine 2015;Shine and Du 2018) may also help to elucidate which behaviours contribute to the goal of maintaining thermal balance.…”

Section: Discussionmentioning

confidence: 99%

“…The thermal gradient may vary between studies, but usually consists of closed chambers with a temperature-controlled stage ranging from cool to warm temperatures that correspond to the range of naturally encountered temperatures by the study system (e.g., Light et al 1966;DeWitt 1967;Hertz et al 1993;Black and Tattersall 2017), ideally without confounding or conflicting cues. The use of thermal gradients presupposes that the costs for thermoregulation are lowered under laboratory conditions, that selected body temperatures (T sel ) reflect the optimal T b for physiological performance typically measured during activity, and that movement within the gradient is a clear indication of thermotaxis (i.e., animals orient along a thermal gradient, and are motivated to move to select or avoid certain temperatures; Doudoroff 1938;Hertz et al 1993;Navas et al 2021). However, for this rationale to be true, some factors must be considered.…”

Section: Introductionmentioning

confidence: 99%

“…This behaviour could be the result of a balance between peripheral thermosensory inputs and motivation to precisely regulate T b by moving toward or away from a heat source, although this remains to be tested (Black and Tattersall 2017). The integrated study of pre-defined behaviours (e.g., rostral orientation and movement) with thermal biology could be the means to ascertain whether animals exhibit positive (move toward the heat source) or negative (move away from the heat source) thermotaxis in the gradient (Black et al 2021;Navas et al 2021). By doing this, one would be prevented from assuming a priori that traits measured within the gradient are indications of thermotaxis.…”

Section: Introductionmentioning

confidence: 99%

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Staying warm is not always the norm: behavioural differences in thermoregulation of two snake species

et al. 2021

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Thermal biology research compares field with laboratory data to elucidate the evolution of temperature-sensitive traits in ectotherms. The hidden challenge of many of these studies is discerning whether animals actively thermoregulate, since motivation is not typically assessed. By studying the behaviours involved in thermoregulation, we can better understand the mechanisms underlying body temperature control. Using an integrative approach, we assessed the thermoregulatory and thermotactic behaviours of two sympatric snake species with contrasting life histories: the generalist Eastern Garter Snake (Thamnophis sirtalis sirtalis ( Linnaeus, 1758 )) and the semi-fossorial Northern Red-bellied Snake (Storeria occipitomaculata occipitomaculata ( Storer, 1839 )). We expected that thermoregulatory behaviours would be optimized based on life history, in that T. s. sirtalis would show higher evidence for thermally oriented behaviours than S. o. occipitomaculata due to its active nature. Thamnophis sirtalis sirtalis actively thermoregulated, had higher thermal preferences (29.4 ± 2.5 vs. 25.3 ± 3.6 °C), and was more active than S. o. occipitomaculata, which showed relatively low evidence for thermotaxis. Our results build on the notion that evaluating movement patterns and rostral orientation towards a heat source can help ascertain whether animals make thermally motivated choices. Our data provide insight into the thermoregulatory strategies used by snakes with different life histories and maximize the information provided by behavioural thermoregulation experiments.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Staying warm is not always the norm: behavioural differences in thermoregulation of two snake species

et al. 2021

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“…Thermoregulatory effectiveness and opportunity for thermoregulation are both limited and highly context‐dependent in shallow waters, which is perhaps one reason why behavioural thermoregulation in aquatic ectotherms has received relatively little attention compared with thermal tolerance (Comte & Olden, 2017; Duarte et al, 2012; Shah et al, 2017). Despite this limitation, many aquatic ectotherms show thermoregulatory behaviour under laboratory thermal gradients (Hutchison & Dupré, 1992; Johnson & Kelsch, 1998), suggesting that they do indeed thermoregulate (but see Navas et al, 2021) where environmental (operative) temperatures provide suitable conditions to do so. In this case, variation in thermoregulatory opportunity should affect ectotherm life‐history traits; however, empirical support for this hypothesis is missing.…”

Section: Introductionmentioning

confidence: 99%

Thermoregulatory opportunity and competition act independently on life‐history traits in aquatic ectotherms

Gvoždı́k

2022

Functional Ecology

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1. Many ectothermic species use behavioural thermoregulation to reduce their exposure to climate change. The buffering effect of behavioural thermoregulation will depend on the time available for an ectotherm to attain a body temperature within the target range, that is, the 'opportunity for thermoregulation'.Behavioural thermoregulation can be further altered by the presence of competitors. Spatiotemporal dynamics in opportunity for thermoregulation and competition intensity should affect variation in ectotherm life history and fitness; however, experimental support for their joint influence is missing.2. I tested this prediction in a mesocosm experiment using larvae of two sympatric amphibians, the alpine newt Ichthyosaura alpestris and the common newt Lissotriton vulgaris. Thermoregulatory opportunities and competition intensities were manipulated by exposing larvae to warmer temperatures and altering densities of con-and heterospecifics. Life-history traits were monitored until metamorphic emergence from the water.3. Thermoregulatory opportunity accelerated differentiation rate and time to metamorphic emergence, while both intra-and interspecific competition affected growth rate and mass at emergence. The impact of competition on survival and injury rates varied between taxa. 4. Thermoregulatory opportunity and competition impacted larval life-history traits in an additive fashion. Suitable conditions for thermoregulation allowed larvae to shorten their developmental period, and thus escape from the aquatic environment earlier than in thermoregulatory challenging environment.Competition was a primary determinant of mass at emergence, which is an important fitness correlate in amphibians. Species-specific survival under competition may contribute to variation in habitat requirements between sympatric taxa. 5. To sum up, predictions on the impact of climate change on ectotherm life histories require information not only about environmental temperatures, but also about species thermoregulatory opportunities and competitive abilities. Thermoregulatory opportunity is an ecologically relevant habitat property not only for basking ectotherms but also for taxa using less conspicuous | 2521

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“…Some frog species exposed to simulated infection do enhance body temperature (Hutchison, 1981; Rowley & Alford, 2013) and produce behavioral fever, so it is logical to predict immunological advantages if this response is exhibited under natural conditions (Bicego & Branco, 2002; Karavlan & Venesky, 2016; Sauer et al, 2019; Woodhams et al, 2003). However, the temperatures selected by amphibians in thermal gradients do not necessarily result from positive thermotaxis, a response presumably required to produce behavioral fever in the field (Navas et al, 2021). Fever is also not the only possible behavioral response to pathogens.…”

Section: Introductionmentioning

confidence: 99%

Behavioral models of hydrothermal regulation in anurans: A field study in the Atlantic Forest, Brazil

et al. 2022

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Anurans rely on different microhabitats and microclimates for hydro‐thermoregulation, which is an important physiological property for locomotor performance, body temperature, water flux, and pathogen defense. We ask whether microhabitat scouting is related to physiological states, specifically if microhabitat choice benefits the production of behavioral fever (e.g., increasing body temperature by selecting warmer places) or sickness behavior (e.g., inactivity and anorexia). We investigated how thermoregulatory behaviors affect hydro‐thermoregulation in anurans, using agar models as a sampling unit, simulating four behaviors related to behavioral fever and sickness behavior. We compared the models' hydro‐thermal balance in two different environments (wet and transitional forests). We showed that the wet forest was warmer and more stable than transitional forest and the agar models in the wet forest were warmer. Still, the four behavioral simulations exhibited similar average temperatures during the five‐day study period in both forests. However, the apathetic behavior models had the lowest daily temperatures. The percentage hydration across models was higher in the wet forest, and daily variation in water loss for each behavioral simulation was higher in the transitional forest. Nevertheless, when limiting the analysis to the warmest times (1000–1600 h), apathetic behavior models lost less water than the others in both forests. We showed that different forests provide microclimatic variation for understory anurans, but different thermoregulatory behaviors may lead to similar body temperatures. Therefore, the Atlantic Forest offers different microclimates and thermoregulation options for anurans, as some species could develop behavioral fever while others demonstrate sickness behavior. Abstract in Portuguese is available with online material.

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Amphibian responses in experimental thermal gradients: Concepts and limits for inference

Cited by 13 publications

References 60 publications

Staying warm is not always the norm: behavioural differences in thermoregulation of two snake species

Staying warm is not always the norm: behavioural differences in thermoregulation of two snake species

Thermoregulatory opportunity and competition act independently on life‐history traits in aquatic ectotherms

Behavioral models of hydrothermal regulation in anurans: A field study in the Atlantic Forest, Brazil

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