Decreased precision contributes to the hypoxic thermoregulatory response in lizards

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SUMMARYAn unequal resource distribution is commonly seen in dominance hierarchies, in which the individual with the higher status is more successful in obtaining the resource. One possible resource is preferred temperature. When situations allow, ectotherms regulate their body temperature by behaviourally selecting different environmental conditions, achieving, when possible, a preferred temperature. Using a shuttlebox, the preferred temperature for Procambarus clarkii was determined to be 23.9°C with upper and lower voluntary escape temperatures of 25.9 and 21.8°C, respectively. If this preferred temperature zone (21.8-25.9°C) was valued as a resource, given the choice between a preferred temperature and a non-preferred temperature, crayfish should compete over the preferred temperature, with the dominant individual of dyadic pairs achieving the preferred temperature more often than the subordinate. Using a dual-choice experimental tank, competition over a binary temperature choice between rankestablished paired crayfish was determined under both warm and cold challenge conditions (warm vs preferred temperature and cold vs preferred temperature, respectively). In naive pairings, similar levels of competition over the preferred temperature occurred in both warm and cold challenge trials, as predicted by game theory. In established pairings, however, dominant crayfish gained significantly greater access to preferred temperature in both warm and cold challenge conditions. These results demonstrate that crayfish engage in a cost-benefit assessment during their initial agonistic contests over temperature, but as hierarchies mature, these thermal games are decided by the dominant animal gaining primary access to the temperature resource.

Section: Thermoregulation In Crayfishsupporting

confidence: 59%

Section: Experimental Procedures Series I: Habituation and Side Bias mentioning

confidence: 99%

Thermal games in crayfish depend on establishment of social hierarchies

Tattersall

Luebbert

LePine

et al. 2012

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“…Before each experiment, lizards were placed in a small incubator (Exo-Terra Thermoelectric Egg Incubator, Rolf C. Hagen Corp., Mansfield, MA, USA) at a temperature of 35°C for a minimum of 45 min to allow for thermal equilibrium at the bearded dragon's preferred body temperature (Cadena and Tattersall, 2009). …”

Section: Methodsmentioning

confidence: 99%

Geographic divergence and colour change in response to visual backgrounds and illumination intensity in bearded dragons

Cadena

Smith

Endler

et al. 2017

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Animals may improve camouflage by both dynamic colour change and local evolutionary adaptation of colour but we have little understanding of their relative importance in colour-changing species. We tested for differences in colour change in response to background colour and light intensity in two populations of central bearded dragon lizards (Pogona vitticeps) representing the extremes in body coloration and geographical range. We found that bearded dragons change colour in response to various backgrounds and that colour change is affected by illumination intensity. Within-individual colour change was similar in magnitude in the two populations but varied between backgrounds. However, at the endpoints of colour change, each population showed greater similarity to backgrounds that were representative of the local habitat compared with the other population, indicating local adaptation to visual backgrounds. Our results suggest that even in species that change colour, both phenotypic plasticity and geographic divergence of coloration may contribute to improved camouflage.

“…In both seasons, the selected T a was lower in hypoxia, in parallel with the decrease in T b . Interestingly the fluctuations in T b were greater in hypoxia than normoxia (Table 3) and might be attributed to a hypoxiainduced decrease in thermosensation and thermoregulatory precision (Cadena and Tattersall, 2009).…”

Section: Hypoxic Thermoregulatory Response In Eastern Chipmunksmentioning

confidence: 97%

Seasonal changes in thermoregulatory responses to hypoxia in the Eastern chipmunk (Tamias striatus)

Levesque

Tattersall

2009

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SUMMARYMammalian heterotherms are known to be more tolerant of low oxygen levels than homeotherms. However, heterotherms demonstrate extreme seasonality in daily heterothermy and torpor expression. Because hypoxia depresses body temperature (T b ) and metabolism in mammals, it was of interest to see if seasonal comparisons of normothermic animals of a species capable of hibernation produce changes in their responses to hypoxia that would reflect a seasonal change in hypoxia tolerance. The species studied, the Eastern chipmunk (Tamias striatus, Linnaeus 1758), is known to enter into torpor exclusively in the winter. To test for seasonal differences in the metabolic and thermoregulatory responses to hypoxia (9.9 kPa), flow-through respirometry was used to compare oxygen consumption, minimum thermal conductance and T b under fixed ambient temperature (T a ) conditions whereas a thermal gradient was used to assess selected T a and T b in response to hypoxia, in both summer-and winteracclimated animals. No differences were observed between seasons in resting metabolism or thermal conductance in normoxic, normothermic animals. Providing the animals with a choice of T a in hypoxia attenuated the hypoxic drop in T b in both seasons, suggesting that the reported fall in T b in hypoxia is not fully manifested in the behavioural pathways responsible for thermoregulation in chipmunks. Instead, T b in hypoxia tends to be more variable and dependent on both T a and season. Although T b dropped in hypoxia in both seasons, the decrease was less in the winter with no corresponding decrease in metabolism, indicating that winter chipmunks are more tolerant to hypoxia than summer animals.