ENVIRONMENTAL AND MATERNAL INFLUENCES ON EMBRYONIC PIGMENTATION IN A TURTLE (TRACHEMYS-SCRIPTA ELEGANS)

Incubation temperature is known to affect pigmentation in turtles and alligators, but the influence of other incubation parameters on pigmen tation has not been reported previously. We examined the pigmentation of hatchling red-eared slider turtles, Trachemys scripta elegans, incu bated under various temperatures and gaseous conditions in the course of three prior studies. Reduced levels of oxygen during embryogenesis did not affect pigmentation, although such levels had produced small s ignificant changes in developmental time. Elevated levels of carbon di oxide during development had a greater influence on pigmentation than did incubation temperature without producing as great a lengthening of incubation time. Hence, the changes in pigmentation produced by tempe rature and carbon dioxide could not be simply a function of their effe cts on developmental time. The carbon dioxide and temperature produced parallel changes in plastral pattern. In contrast, carbon dioxide had marked effects on skin pigmentation that were not paralleled by those of temperature. In addition, there were some significant differences among clutches in the effects of incubation temperature and carbon dio xide on pigmentation. Some of the differences in pigmentation among in cubation treatments for this species are similar in magnitude to those occurring naturally among related turtle species. The ability to alte r various developmental sequences differentially by changes in incubat ion conditions will facilitate both developmental and comparative evol utionary studies.