Timbal muscle physiology in the endothermic cicada Tibicen winnemanna (Homoptera : Cicadidae)

The operative muscle temperature and contraction kinetics are described for the endothermic cicada Tibicen winnemanna (Davis). Measurements of timbal muscle temperature in the field demonstrate that timbal muscle temperature is elevated above ambient temperature during activity. Timbal muscle temper ature increases as the acoustic output progresses from a 'warm-up' buzz (27 .9-29.7 degreesC) to full song production (36.3-39.5 degrees). Mean muscle- ambient temperature difference increases from 5.8 degreesC in buzzing anima ls to 13.1 degreesC in animals producing a full calling song. Twitch rise t ime and onset to 50% relaxation time decrease while tension production incr eases with increasing temperature to 40 degreesC. Mean force production at 20 degreesC was determined to be 0.22 +/-0.06 N/cm(2), The characteristics of T. winnemanna muscle are similar to those reported in other cicada speci es. Analysis of the songs produced by animals with one timbal destroyed and the sounds produced by mechanical manipulation suggest that the timbals al ternately contract and relax in the sequence IN1-IN2-OUT1-OUT2. Measurement s of the inferred period of muscle contraction from song recordings and the contraction kinetics of isolated timbal muscles measured in the laboratory show that the temperature of the timbal muscle must be elevated in order f or the cicada to be able to produce the calling song. (C) 2001 Elsevier Sci ence Inc. All rights reserved.