PARENT SESSION
Oral Session #65: Aquatic Ecology: Stream and Lake.
Presiding: C. Osenberg
Wednesday, August 7. 1:00 PM to 4:45 PM. Coconino Meeting Room, TCC.

Why are streamside salamander larvae dark on a light substrate? Effects of multiple factors on color and color change in sister species of Ambystoma.

Garcia, Tiffany^*,1, Sih, Andrew², ¹ University of Kentucky, Lexington, Kentucky² Univeristy of California at Davis, Davis, California

ABSTRACT- I investigated multiple factors that influence color change in larvae of two sister species of salamanders. Ambystoma barbour, a stream dwelling species, has a darker mean body color than its sister species, A. texanum, which inhabits ponds. Interestingly, neither species cryptically matches its background. The difference in mean color between species could be an adaptive response to higher ultraviolet radiation (UVR) exposure in shallow, clear streams relative to murky ponds. Exposure to ambient UVR caused larvae of both species to darken. A time of day effect was also found, with both species dramatically darker in the day than at night, presumably due to UVR exposure. Temperature also played an important role in determining larval color in both species. Interestingly, this effect was age-dependent. Newly hatched larvae became darker in cold water, but this effect was not present in later staged larvae. In both species, older larvae grew lighter in color regardless of temperature. This age x temperature pattern might be an adaptive response to predictable, seasonal changes in temperature and UVR regimes. In the cold, early spring, larvae might benefit by foraging in warmer, shallow waters. This exposes them to high UVR levels, particularly because the tree canopy has not yet filled in. Later in the season, the canopy provides shade from high UVR, and water temperatures are warmer. Older larvae probably have less need to be dark as protection from UVR.

KEY WORDS: ultraviolet radiation, temperature, Ambystoma, color