Meeting Abstract
Body temperature (Tb) regulation requires the balance between heat gain and losses to the environment and adjusts in metabolic heat production. If Tb is elevated, heat dissipation can be increased by changes in microhabitat selection, body posture, erection or bristling of fur or feathers, and peripheral vasomotor responses. In terrestrial animals, heat dissipation is also assisted by evaporative cooling. Evaporation can occur from humid body surfaces or from watery fluids exposed to the environment by different avenues, for example, by sweating, salivation and licking, and panting. In most insects, evaporative cooling is constrained by their impermeable exoskeleton, while their small size makes them particularly susceptible to heat gain. Herein, we describe a novel thermoregulatory behavior in which the blowfly, Chrysomya megacephala, moves tidally a saliva droplet out and then back into the foregut in order to attain the benefits of evaporative cooling. As revealed by infrared thermography, as the saliva droplet is moved outwards, evaporation cools the fluid and, upon its re-ingestion, it cools the fly´s body tissues. Saliva droplet movements are driven by the pharyngeal pump and saliva can be pooled underneath the brain, possibly facilitating brain cooling. The occurrence of the saliva droplet tidal movements is influenced by ambient temperature and relative humidity. The use of a dynamically moved saliva droplet represents an entirely novel modality to interface a watery fluid to the environment in order to attain the benefits of evaporative cooling. Financial support: São Paulo Research Foundation (FAPESP)
