Influences of thermal and hydric environments on incubation eggs and hatchling phenotypes of white-striped grass lizards Takydromus wolteri (Lacertidae)

Influences of thermal and hydric environments on incubation eggs, embryonic use of energy and hatchling phenotypes were studied in the white-striped grass lizard Takydromus wolteri, which were collected at Langyashan Mountain, Chuzhou, Anhui, Eastern China. The eggs were incubated at three constant (27℃, 30℃, and 33℃) and one fluctuating temperatures on substrates with water potentials of 0 and -220 kPa using a 4×2 factorial design. Eggs were incubated in plastic containers that were covered with a perforated plastic membrane. Eggs were 1/3-buried in the substrate, with the surface near the embryo exposed to air inside the container. We weighed containers daily and, if necessary, water were added to the vermiculite to compensate for small evaporative losses and absorbed by eggs. Eggs were weighed at 5 day intervals.Upon emergence, each hatchling was measured, weighed, examined for locomotor performance, and then killed by freezing to -15℃ for later studies. Each hatchling was separated into carcass, fat bodies, and residual yolk. The three components were dried in an oven at 65℃ to constant mass, and then weighed. We extracted non-polar lipids from dried samples in a Soxhlet apparatus for a minimum of 5.5 h using absolute ether as solvent. We determined energy density of dried samples using an adiabatic bomb calorimeter. We determined ash content in each sample using a muffle furnace at 700℃ for a minimum of 12 h and weighing the remaining ash.All viable eggs increased in mass over the course of incubation due to absorption of water, and mass gain during incubation was dependent on initial egg mass and substrate water potential. There were no differences of the incubation length, hatching success, sex ratio, and hatchlings size in the two examined substrate moisture. Incubation length decreased as incubation temperature increased. The average duration of incubation at 27℃, 30℃, and 33℃ was 32.5℃, 24.9℃, and 23.0 d, respectively; the duration of incubation at fluctuating temperatures average 31.1 d. Incubation temperature did not influence hatching success and sex ratio of hatchlings, but profoundly affected embryonic use of nutrients, hatchlings size and hatchlings body mass, and carcass mass. Eggs at 33℃ produced hatchlings with less developed carcass, greater amount of unutilized yolk and worse sprint speed. 27℃ and fluctuating temperature treatments produced well-developed hatchlings, and the measured phenotype traits were nearly the same. Taken together, our results showed that 27℃-30℃ and fluctuating temperature are suit for egg incubation in T.wolteri.