Analysis of heart rate control to assess thermal sensitivity responses in
Brazilian toads |
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Authors: | JES Natali BT Santos VH Rodrigues JG Chauí-Berlinck |
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Institution: | Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brasil |
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Abstract: | In anurans, changes in ambient temperature influence body temperature and, therefore,
energy consumption. These changes ultimately affect energy supply and, consequently,
heart rate (HR). Typically, anurans living in different thermal environments have
different thermal sensitivities, and these cannot be distinguished by changes in HR.
We hypothesized that Rhinella jimi (a toad from a xeric environment
that lives in a wide range of temperatures) would have a lower thermal sensitivity
regarding cardiac control than R. icterica (originally from a
tropical forest environment with a more restricted range of ambient temperatures).
Thermal sensitivity was assessed by comparing animals housed at 15° and 25°C. Cardiac
control was estimated by heart rate variability (HRV) and heart rate complexity
(HRC). Differences in HRV between the two temperatures were not significant (P=0.214
for R. icterica and P=0.328 for R. jimi), whereas
HRC differences were. All specimens but one R. jimi had a lower HRC
at 15°C (all P<0.01). These results indicate that R. jimi has a
lower thermal sensitivity and that cardiac control is not completely dependent on the
thermal environment because HRC was not consistently different between temperatures
in all R. jimi specimens. This result indicates a lack of evolutive
trade-offs among temperatures given that heart rate control at 25°C is potentially
not a constraint to heart rate control at 15°C. |
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Keywords: | Anuran Cardiac control Heart rate complexity Heart rate variability Thermal physiology |
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