Large-scale changes in thermal sensitivity of flight performance
during adult maturation in a dragonfly
James H. Marden
Journal of Experimental Biology 198, 2095-2102.
Newly emerged adult dragonflies are physiologically immature in a number
of ways, including mass, ultrastructure, and biochemistry of their flight
muscles. In Libellula pulchella dragonflies, adult maturation of
flight muscle is accompanied by striking changes in thermal physiology.
Vertical force production during fixed flight attempts in newly emerged
adults (tenerals) shows a broad plateau of near-peak performance, first
attained at cool thoracic temperatures (typically 28-34oC)
and maintained up to thoracic temperatures of 40-45oC (mean optimal
thoracic temperature [OTT] = 34.6oC; mean upper lethal temperature
[ULT] = 45.3oC). In contrast, fully mature adults show narrow
thermal sensitivity curves, wherein peak performance is approached only
within a few degrees of the thermal optimum, which invariably occurs at
hot thoracic temperatures (38-50oC; mean OTT = 43.5oC;
mean ULT = 48.6oC). These changes in the shape and position of
thermal performance curves are compared with predictions from hypotheses
for the evolution of thermal sensitivity.
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