Abstracts 2011 - Framingham State University

Billion Ao
Heating and cooling rate of Morelia
amethistina.
Heating and cooling rates determine the time required to reach a preferred
temperature range and the amount of time an organism can stay in that range. For
majority of ectotherms, heating rate is higher than cooling rate to extend the amount of
time within a preferred temperature range. Factors such as body size (kg) can
influence these rates in predictable ways by manipulating surface area to volume
ratios. Scrub pythons (Morelia amethistina), which are large tropical pythons, exhibit
large body size variation from hatchling to adult. The goal of this experiment was to
test if scrub pythons heated faster than cooled, and if their large change in body size
affects these rates. The pythons (n=7) were heated and cooled in a hot (32.2 o C) and
cold chambers (22.2 o C). Heating rate and cooling time constants (τ) of snakes were
compared to operative models (n = 3), which were used to simulate the time constants
of an inanimate object (i.e., an object without behavioral or physiological mechanisms).
Heating rates of the scrub pythons (160 ± 76 min, mean ± SD) were significantly higher
(p = 0.005) than cooling rates (229 ± 61 min, mean ± SD). The scrub pythons heated
and cooled significantly slower (p = 0.03, p < 0.0001, respectively) than the operative
models. Scrub pythons showed positive allometry in their heating tau (0.51) and
negative allometry in their cooling tau (0.22) when compared to the predicted isometric
scaling constant (0.33). Scrub pythons either physiologically or behaviorally regulate
their heating and cooling rates. Morelia amethistina heated and cooled like many other
ectotherms and show that as size increases heating and cooling rates slowed.
Photographed by Dr. Dinkelacker
Tau (min)
350
300
250
200
150
100
50
0
Mean tau of scrub pythons and models
*
*
Snake Heating Snake Cooling Model Heating Model Cooling
*P-value < 0.01