The Seasonal Acclimatisation of Locomotion in a Terrestrial Reptile, Plestiodon chinensis(Scincidae)

Studies of the seasonal acclimatisation of behavioural and physiological processes usually focus on aquatic or semi-aquatic ectotherms and focus less effort on terrestrial ectotherms that experience more thermally heterogeneous environments. We conducted comparative studies and thermal acclimation experiments on the locomotion of the Chinese skink （Plestiodon chinensis） to test whether seasonal acclimatisation in locomotion exists in these terrestrial ectothermic vertebrates, and whether seasonal acclimatisation is predominantly induced by thermal environments. In natural populations, skinks ran faster during the summer season than during the spring season at high-test temperatures ranging from 27℃ to 36℃ but not at low-test temperatures ranging from 18℃ to 24℃. In contrast, the thermal acclimation experiments showed that the cold-acclimated skinks ran faster than the warm-acclimated skinks at the low- test temperatures but not at high-test temperatures. Therefore, the seasonal acclimatisation occurs to P chinensis, and may be induced by temperature as well as other factors like food availability, as indicated by the seasonal variation in the thermal dependence of locomotion, and the discrepancy between seasonal acclimatisation and thermal acclimation on locomotion.

Offspring Sex Is Not Determined by Gestation Temperature in a Viviparous Lizard(Eremias multiocellata) from the Desert Steppe of Inner Mongolia

Sex-determining systems show a striking diversity not only among species, but also among popula tions. In reptiles, sex-determina tion is a continuum, from tempera ture-dependent sex determination(TSD) to genetic sex determination(GSD).The multi-ocellated racerunner(Eremias multiocellata)is reported to be a cryptic ZZ/ZW chromosomal TSD species, with male-biased sex ratios at high temperatures in two Gansu populations. However, the generality of the sex-determining pattern in different populations of this species remains unclear. To investigate the mode of sex determina tion in a popula tion of E.multiocellata from the desert steppe of Inner Mongolia,we first identified sex chromosomes via comparative genomic hybridization(CGH). We then conducted a thermal manipulation experiment to determine the effect of gestation temperature on offspring sex ratios.From the CGH studies we found that lizards from the Inner Mongolia population possessed ZZ/ZW sex chromosomes. However, our thermal manipulation experiment showed that gestation temperature did not affect the sex ratio of neonates in this population. In combination, these results rule out TSD in the Inner Mongolia population of E. multiocellata, and suggest that there is widespread geographic variation in the sexdetermining system of this species.

Reduced egg shell permeability affects embryonic development and hatchling traits in Lycodon rufozonatum and Pelodiscus sinensis

The response of embryos to unpredictable hypoxia is critical for successful embryonic development,yet there remain significant gaps in our understanding of such responses in reptiles with different types of egg shell.We experimentally generated external regional hypoxia by sealing either the upper half or bottom half of the surface area of eggs in 2 species of reptiles(snake[Lycodon rufozonatum]with parchment egg shell and Chinese softshelled turtle[Pelodiscus sinensis]with rigid egg shell),then monitored the growth pattern of the opaque white patch in turtle eggs(a membrane that attaches the embryo to the egg shell and plays an important role in gas exchange),the embryonic heart rate,the developmental rate and the hatchling traits in turtle and snake eggs in response to external regional hypoxia.The snake embryos from the hypoxia treatments facultatively increased their heart rate during incubation,and turtle embryos from the upper-half hypoxia treatment enhanced their growth of the opaque white patch.Furthermore,the incubation period and hatching success of embryos were not affected by the hypoxia treatment in these 2 species.External regional hypoxia significantly affected embryonic yolk utilization and offspring size in the snake and turtle.Compared to sham controls,embryos from the upper-half hypoxia treatment used less energy from yolk and,therefore,developed into smaller hatchlings,but embryos from the bottom-half hypoxia treatment did not.

Experimental evaluation of reproductive response to climate warming in an oviparous skink

The impact of climate warming on organisms is increasingly being recognized.The experimental evaluation of phenotypically plastic responses to warming is a critical step in understanding the biological effects and adaptive capacity of organisms to future climate warming.Oviparous Scincella modesta live in deeply-shaded habitats and they require low optimal temperatures during embryonic development,which makes them suitable subjects for testing the effects of warming on reproduction.We raised adult females and incubated their eggs under different thermal conditions that mimicked potential climate warming.Female reproduction,embryonic development and hatchling traits were monitored to evaluate the reproductive response to warming.Experimental warming induced females to lay eggs earlier,but it did not affect the developmental stage of embryos at oviposition or the reproductive output.The high temperatures experienced by gravid females during warming treatments reduced the incubation period and increased embryonic mortality.The locomotor performance of hatchlings was not affected by the maternal thermal environment,but it was affected by the warming treatment during embryonic development.Our results suggest that climate warming might have a profound effect on fitness-relevant traits both at embryonic and post-embryonic stages in oviparous lizards.

CRH Neurons in the Laterodorsal Tegmentum Mediate Acute Stress-induced Anxiety

Dear Editor,Acute stress-induced anxiety is pervasive in both animals and humans.The natural stress response effectively helps animals to maintain arousal,flee from danger,or simply stay alert to their surroundings.On the other hand,excessive anxiety is strongly associated with many severe psychiatric disorders such as depression,phobia,and posttraumatic stress disorder(PTSD).Although the probability of an individual suffering clinical anxiety reaches an average of 28%during their lifetime,the underlying neural mechanisms of anxiety remain poorly understood.