We collected adult females of Dinodon rufozonatum (Colubridae) from a population in Zhejiang, Southeast China, to study the effects of incubation temperature on embryonic metabolism and hatchling behavior. We incubated eggs at there constant temperatures ranging from 24 ℃ to 30 ℃, and weighed containers and eggs at 5-day intervals. The duration of incubation, measured as the number of days to pipping, was recorded for each egg. Eggs were measured for changes in size and embryonic metabolism at 5-day intervals. The response to chemical cues, respiration metabolism and sexual phenotype were determined for each hatchling. Because physiological and behavioral performances are highly sensitive to variation in body temperature in reptiles, we conducted all trials at the body temperature of 28 ℃. This was achieved by placing hatchlings in an incubator at the test temperature for approximately 1 h prior to testing. We presented a cotton-tipped applicator soaked with cologne water to the lip of hatchlings and recorded tongue flicks for 1 min. Tongue flicking was measured because many reptiles flick their tongues frequently to detect both predators and prey and to gather information about other members of their own species. The behavioral character is therefore a potentially important indicator of fitness.
Incubation temperature affected incubation length, mass gain and energy consumption of eggs during incubation and locomotor performance of hatchlings, but not the rate of embryonic metabolism, hatchling success and tongue flicking. Incubation length decreased exponentially as incubation temperature increased. All eggs gained mass during incubation due to absorption of water. Incubation temperature affected water exchanges between eggs and their surroundings, thereby affecting the hydric conditions inside the egg. Eggs incubated at 24 ℃ gained more mass and comsumed more energy to hatch than did eggs at 30 ℃, but eggs incubated at these two temperatures did not differ from eggs incubated at 27 ℃ in mass gain and energy consumption during incubation. Swimming speed was greatest in hatchlings incubated at 27 ℃ and lowest in hatchling incubated at 24 ℃, with hatchlings incubated at 30 ℃ in between. Hatchlings incubated at the three temperatures did not differ from each other in tongue flicking.
The carbon dioxide breathed out by eggs decreased as incubation temperature increased. The amount of energy consumed by embryos developing at 24, 27 and 30 ℃ during incubation was 6.63, 4.42 and 3.42 J, respectively. This result better explains why hatchlings incubated at lower temperatures are larger in snout-vent length and heavier than those incubated at higher temperatures. Though the rate of embryonic metabolism did not differ among three temperature treatments, incubation length was longer at lower than at higher temperatures so that embryons at lower temperatures needed more energy to complete development. This explains why hatchlings from eggs incubated at lower temperatures had more residual yolks than did those from higher incubation temperature.
Our results reveal that incubating eggs at temperatures ranging from 24-30 ℃ does not have important effects on embryonic metabolism and hatchlings behavior in D. rufozonatum. This temperature range seems like temperature at habitat of D. rufozonatum.