Evaporative cooling and endothermy in the 13-year periodical cicada, Magicicada tredecem (Homoptera: Cicadidae)

Autor: Eric C. Toolson, Elizabeth K. Toolson
Rok vydání: 1991
Předmět:
Zdroj: Journal of Comparative Physiology B. 161:109-115
ISSN: 1432-136X
0174-1578
DOI: 10.1007/bf00258754
Popis: The thermobiology of a cicada, Magicicada tredecem, from a warm, high humidity environment was investigated. Thoracic temperature (Tth) of M. tredecem in the field was strongly dependent on, and consistently higher than, ambient temperature (Tam), averaging 33.0±0.19°C on warm sunny days (Tam=28–29°C, rh=60–75%). Laboratory studies documented cuticle water fluxes high enough (≈ 5mg · cm−2 · h−1 in dry air at 40°C) to result in a significant degree of passive evaporative cooling, but the ability of M. tredecem to actively facilitate evaporative water loss during thermal stress is comparatively limited: water loss rates (WLR) of live M. tredecem at 40°C (dry air) were only 35–45% greater than those of dead cicadas. The limited ability of M. tredecem to facilitate transcuticular WLR is associated with limited surface distribution of the cuticular ducts through which water is actively extruded during evaporative cooling. In the laboratory, active extrusion of water had no appreciable effect on Tth, demonstrating that evaporative cooling was due largely to passive water flux through the highly permeable cuticle. The location of the abdominal pore tracts is such that extrusion of water through the ducts may preferentially cool the heart and perhaps other abdominal tissues. Long-term climatological data indicate that M. tredecem rarely encounters Tam levels high enough (i.e., above its apparent Tth setpoint of 34–35°C) to require evaporative cooling. Inactive M. tredecem can endothermically increase Tth. An hypothesis is proposed to account for the diversity of body temperature setpoints in cicadas.
Databáze: OpenAIRE
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