Effects of ozone on evaporative water loss and thermoregulatory behavior of marine toads (Bufo marinus)

Ozone (O(3)) 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 O(3) exhibit a pronounced decrease in core body temperature at rest, which may offer a protective effect against O(3) damage. The effects of O(3) on other vertebrates have not been studied. Compared to individuals exposed to air (N=34), Bufo marinus toads exposed to O(3) (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 O(3) (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 O(3) exposure on the preferred body temperatures (PBT) of toads. However, O(3) 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.