Effects of Ozone on Evaporative Water Loss and Thermoregulatory Behavior of Marine Toads (Bufo marinus)

Ozone (O3) is a strong pulmonary irritant and causes a suite of respiratory tract inflammatory responses in humans and other mammals. In addition to lung injury, rodents exposed to O3 exhibit a pronounced decrease in core body temperature at rest, which may offer a protective effect against O3 damage. The effects of O3 on other vertebrates have not been studied. Compared to individuals exposed to air (N=34), Bufo marinus toads exposed to O3 (N=32) for 4 h lost 3.78 g body mass (adjusted mean from analysis of covariance, body mass mean±SD, 90.1±21.90 g). We tested the thermoregulatory responses of 22 toads in a thermal gradient 1, 24, and 48 h after 4-h exposure to air (N=11) or 0.8 ppm O3 (N=11). Individual toad thermal preferences were also significantly repeatable across all trials (intraclass CORRELATION=0.66, P <0.001). We did not observe a direct effect of O3 exposure on the preferred body temperatures (PBT) of toads. However, O3 exposure did have an indirect effect on selected temperatures. Ozone-exposed toads with higher evaporative water loss rates, in turn, also selected lower PBT, voluntary minimum, and voluntary maximum temperatures 24 h post-exposure. Ozone exposure may thus alter both water balance and thermal preferences in anuran amphibians.