Effect of body mass and melanism on heat balance in Liolaemus lizards of the goetschi clade

MORENO AZÓCAR, DÉBORA LINA; BONINO, MARCELO FABIÁN; PEROTTI MARIA GABRIELA; SCHULTE II, J.A.; ABDALA, CRISTIAN SIMÓN; CRUZ, FÉLIX BENJAMÍN

JOURNAL OF EXPERIMENTAL BIOLOGY

COMPANY OF BIOLOGISTS LTD

Lugar: Cambridge; Año: 2016 vol. 219 p. 1162 - 1171

0022-0949

Body temperature of ectotherms depends on the environmental temperatures and behavioral adjustments, but morphology may also affect it. For example, in colder environments animals tend to be larger and show higher thermal inertia, as proposed by Bergmann´s rule and the heat balance hypothesis (HBH). Additionally, dark coloration increases solar radiation absorption and should accelerate heat gain (Thermal melanism hypothesis, TMH).We tested Bergmann´s rule, HBH and TMH within the Liolaemus goetschi lizards clade that show variability in body size and melanic coloration. We measured heating and cooling rates of live and euthanized animals, and tested how morphology and color affect these rates. Live organisms show less variable and faster heating rates, compared to cooling rates, suggesting behavioral and/ or physiological adjustments.Our results support Bergmann´s rule and the HBH, as larger species show slower heating and cooling rates. However, we did not find a clear pattern to support TMH. The influence of dorsal melanism on heating by radiation was masked by body size effect in live animals, while results from euthanized individuals show no clear effects of melanism on heating rates either. However, when compared three groups of live individuals with different degree of melanism we found that that darker euthanized animals actually heat faster than lighter ones, favoring TMH. Although unresolved aspects remain, body size and coloration influenced heat exchange suggesting complex thermoregulatory strategies in these lizards, probably regulated through physiology and behavior, what may allow these small lizards to inhabit harsh weather environments