Thermoregulation by Endogenous Heat Production in Two South American Grass Dwelling Cicadas (Homoptera: Cicadidae: Proarna)
Abstract
Proarna bergi (Distant) and Proarna insignis Distant use metabolic heat to raise body temperature (Tb) for activity when ambient conditions would prevent activity in ectothermic animals. Both species were observed singing during overcast or rainy conditions and at dusk. Tbs in the field exceeded ambient by as much as 7.4C when solar radiation was unavailable to the insects. In the laboratory voluntary metabolic heat production raised Tb as much as 12.3C and 10.7C above ambient in P. bergi and P. insignis respectively. Estimates of metabolic rate from heating and cooling curves were 0.118 ml O2 per min for P. bergi and 0.126 ml O2 per min for P. insignis. Fine shiver-like movements of the thoracic musculature produced the heat. The Tb at which endogenous warm-up voluntarily stopped in the laboratory was similar to the Tbs measured in active animals in the field. Thermal responses measured in the laboratory also illustrate these animals are thermoregulating with endogenous heat. Endogenous heat production uncoupled reproductive behavior from environmental constraints.Downloads
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