We incubated eggs ofPlestiodon chinensis under five constant (24, 26, 28, 30, and 32 ℃) and one fluctuating thermal regimes to examine the effects of constant versus fluctuating incubation temperatures on hatching ...We incubated eggs ofPlestiodon chinensis under five constant (24, 26, 28, 30, and 32 ℃) and one fluctuating thermal regimes to examine the effects of constant versus fluctuating incubation temperatures on hatching success, incubation length, and hatchling morphology. The duration of incubation varied considerably among the six temperature treatments, whereas hatching success did not. The mean incubation length decreased as temperature increased in a nonlinear way, and increased as the thermal variance increased. Incubation temperature affected the body size (linear length and mass) and shape of hatchlings, with eggs incubated at 26, 28, and 30 ℃ producing larger and heavier hatchlings than did those incubated at 24 ℃, 32 ℃, or fluctuating temperatures. Our results showed that exposure of P. chinensis eggs to extreme temperatures for brief periods of time did not increase embryonic mortality and, in the fluctuating-temperature treatment, the thermal variance affected hatchling morphology more evidently than the thermal mean. Our results highlight the importance of the thermal variance in affecting embryonic development and hatchling morphology, and add further evidence that temperatures within the range of 26-30 ℃ are optimal for P. chinensis embryos.展开更多
We collected 24 gravid female Chinese skinks(Plestiodon chinensis) to study embryonic growth and yolk depletion during incubation. Females laid eggs between late May and mid-June. Eggs were incubated at 24(± 0.3)...We collected 24 gravid female Chinese skinks(Plestiodon chinensis) to study embryonic growth and yolk depletion during incubation. Females laid eggs between late May and mid-June. Eggs were incubated at 24(± 0.3) ℃. One egg from each clutch was dissected at 5-d intervals starting at laying. Embryonic stages at laying varied from Dufaure and Hubert's(1961) Stage 30-35, with a mean stage of 32.6. Incubation lengths at 24 ℃ varied from 35.1 to 48.3 d, with a mean of 41.5 d. Based on the derived functions describing instantaneous changes in embryo dry mass and yolk dry mass, we identified three phases of embryonic growth or yolk depletion in P. chinensis. Phase 1, from Day 0(at laying) to Day 15(~36% of the way through incubation), was one of minimal transfer of material from yolk to embryo. Phase 2, from Day 15 to Day 32-33(~77%-80% of the way through incubation), was characterized by increasingly rapid embryonic growth or yolk depletion. Phase 3, from Day 32-33 to hatching, was characterized by reduced embryonic growth or yolk depletion. The length of the last embryonic stage(Stage 40 = completely differentiated embryos) accounted for about 28% of incubation length, and the dry mass of the smallest embryos of Stage 40 accounted for only ~48% of the hatchling dry mass. Our study adds evidence to the idea that oviposition is not timed to coincide with the onset of rapid embryonic growth in oviparous reptiles, and is first to demonstrate that ~50% embryonic growth occurs in the last quarter of incubation in P. chinensis.展开更多
基金the National Natural Science Foundation of China (31470471 and 30670281)the Zhejiang Provincial Natural Science Foundation (LY17C030003)the Priority Academic Development Program of Jiangsu Higher Education Institutions
文摘We incubated eggs ofPlestiodon chinensis under five constant (24, 26, 28, 30, and 32 ℃) and one fluctuating thermal regimes to examine the effects of constant versus fluctuating incubation temperatures on hatching success, incubation length, and hatchling morphology. The duration of incubation varied considerably among the six temperature treatments, whereas hatching success did not. The mean incubation length decreased as temperature increased in a nonlinear way, and increased as the thermal variance increased. Incubation temperature affected the body size (linear length and mass) and shape of hatchlings, with eggs incubated at 26, 28, and 30 ℃ producing larger and heavier hatchlings than did those incubated at 24 ℃, 32 ℃, or fluctuating temperatures. Our results showed that exposure of P. chinensis eggs to extreme temperatures for brief periods of time did not increase embryonic mortality and, in the fluctuating-temperature treatment, the thermal variance affected hatchling morphology more evidently than the thermal mean. Our results highlight the importance of the thermal variance in affecting embryonic development and hatchling morphology, and add further evidence that temperatures within the range of 26-30 ℃ are optimal for P. chinensis embryos.
基金National Natural Science Foundation of China (31470471)
文摘We collected 24 gravid female Chinese skinks(Plestiodon chinensis) to study embryonic growth and yolk depletion during incubation. Females laid eggs between late May and mid-June. Eggs were incubated at 24(± 0.3) ℃. One egg from each clutch was dissected at 5-d intervals starting at laying. Embryonic stages at laying varied from Dufaure and Hubert's(1961) Stage 30-35, with a mean stage of 32.6. Incubation lengths at 24 ℃ varied from 35.1 to 48.3 d, with a mean of 41.5 d. Based on the derived functions describing instantaneous changes in embryo dry mass and yolk dry mass, we identified three phases of embryonic growth or yolk depletion in P. chinensis. Phase 1, from Day 0(at laying) to Day 15(~36% of the way through incubation), was one of minimal transfer of material from yolk to embryo. Phase 2, from Day 15 to Day 32-33(~77%-80% of the way through incubation), was characterized by increasingly rapid embryonic growth or yolk depletion. Phase 3, from Day 32-33 to hatching, was characterized by reduced embryonic growth or yolk depletion. The length of the last embryonic stage(Stage 40 = completely differentiated embryos) accounted for about 28% of incubation length, and the dry mass of the smallest embryos of Stage 40 accounted for only ~48% of the hatchling dry mass. Our study adds evidence to the idea that oviposition is not timed to coincide with the onset of rapid embryonic growth in oviparous reptiles, and is first to demonstrate that ~50% embryonic growth occurs in the last quarter of incubation in P. chinensis.
基金Acknowledgments This study was supported by grants from the National Science Foundation of China (Project No. 30670281) and the Zhejiang Provincial Department of Education (Project No. Y200908723). We thank Lai-Gao Luo, Long-Hui Lin, Yan-Fu Qu, Xi-Dong Zhang, Hong Li and Hong-Xia Liu for their help during the research.
基金The work was carried out in compliance with the current laws of China, and was supported by grant from Priority Academic Program Development of Jiangsu Higher Education Institutions to Ji's group, the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Project No. llKJB180004), Jiangsu Provincial Foundation of Natural Science (No. BK2012849) and the Natural Science Foundation of China (No. 31070339). We would like to thank Long-Hui Lin, Jian-Fang Gao, Lai-Gao Luo andYan-Fu Qu for their assistance both in the field and in the laboratory.