Effects of hydroperiod duration on developmental plasticity in tiger frog （Hoplobatrachus chinensis） tadpoles

While developmental plasticity can facilitate evolutionary diversification of organisms, the effects of water levels as an environmental pressure on tiger frogs remains unclear. This study clarifies the relationship by studying the responses of tiger frog （Hoplobatrachus chinensis） tadpoles to simulated hydroperiods （i.e., constant low water levels, constant high water levels, increasing water levels, decreasing water levels, rapid changes in water levels and gradual fluctuations in water levels） in a laboratory setting. ANOVA analysis showed that none of the water level treatments had any significant effect on the total length, body mass, or developmental stages of H. chinensis tadpoles half way through development （11 days old）. Tadpoles raised in rapidly fluctuating water levels had protracted metamorphosis, whereas tadpoles raised under low and gradually fluctuating water levels had shortened metamorphosis. None of the water level treatments had a significant effect on the snout-vent length （SVL） or body mass of H. chinensis tadpoles at Gosner stage 42, or on the body mass of tadpoles at Gosner stage 45. However, the＇ tadpoles raised in high levels and rapidly fluctuating water levels, significantly larger SVL at Gosner stage 45, while ones under gradually fluctuating water levels had smaller SVL than the other groups. Time to metamorphosis was positively correlated with body size （SVL） at metamorphosis in H. chinensis tadpoles. H. chinensis tadpoles under constant low water level had the highest mortality rate among all the treatments （G-test）. Moreover, ANOVA and ACNOVA （with body length as the covariate） indicated that water levels had no significant effect on either the morphology （i.e. head length, head width, forelimb length, hindlimb length and body width） or the jumping ability of juvenile H. chinensis. These results suggest that the observed accelerated metamorphosis and high mortality of H. chinensis tadpoles under decreasing water level treatment was driven by density-induced physical interaetions among increasing conspeeifics.

Phenotypic Plasticity in Embryonic Development of Reptiles:Recent Research and Research Opportunities in China

Adaptive developmental plasticity can enable an organism to modify its phenotype rapidly, in response to local （and perhaps, unpredictable） conditions, by altering reaction norms during development. Previous studies on this topic have been dominated by western scientists, employing western study systems and approaches. Recently, the expansion of Chinese ecological research has seen a broadening of studies taxonomically （phylogenetically）. Here, we briefly summarize research that has been conducted on developmental plasticity in Chinese reptiles over the past two decades, and suggest productive directions for future studies in this field. There are exciting research opportunities in this field in China, and we call for increased collaboration between western and eastern scientists to elucidate the role of developmental plasticity in evolutionary responses of organisms to environmental changes. As human activities increase the intensity and frequency of such changes, the need to understand responses of biological systems becomes an increasingly urgent priority.

Basic Research on Brain Development and Neural Plasticity Kicked Off

A major basic research projectin the field of neurosciencewas launched on November26 last year at the Shanghai-basedInstitute of Neuroscience of the Chi-nese Academy of Sciences(CAS).

How incubation temperature affects hatchling performance in reptiles: an integrative insight based on plasticity in metabolic enzyme

Evaluating the effects of temperature variations on animals plays an important role in understanding the threat of climate warming.The effects of developmental temperature on offspring performance are critical in evaluating the effects of warming temperatures on the fitness of ovipa-rous species,but the physiological and biochemical basis of this developmental plasticity is largely unknown.In this study,we incubated eggs of the turtle Pelodiscus sinensis at low(24℃),medium(28℃),and high(32℃)temperatures,and evaluated the effects of developmental temperature on offspring fitness,and metabolic enzymes in the neck and limb muscles of hatchlings.The hatchlings from eggs incubated at the medium temperature showed better fitness-related performance(righting response and swimming capacity)and higher activities of metabolic enzymes(hexokinase,HK;lactate dehydrogenase,LDH)than hatchlings from the eggs incubated at high or low temperatures.In addition,the swimming speed and righting response were significantly correlated with the HK activities in limb(swimming speed)and neck(righting response)muscles,suggesting that the developmental plasticity of energy metabolic pathway might play a role in determining the way incubation temperature affects offspring phenotypes.Integrating the fitness-related performance and the activities of metabolic enzymes,we predict that the P sinensis from high latitude would not face the detrimental effects of climate warming until the average nest temperatures reach 32℃.

Effects of Constant versus Fluctuating Incubation Temperatures on Hatching Success, Incubation Length, and Hatchling Morphology in the Chinese Skink (Plestiodon chinensis)

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.

Maternal Thermal Effects on Female Reproduction and Hatchling Phenotype in the Chinese Skink(Plestiodon chinensis)

We maintained gravid Chinese skinks(Plestiodon chinensis) at three constant temperatures(25, 28 and 31 °C) during gestation, and randomly assigned eggs from each female to one of the same three temperatures for incubation to determine maternal thermal effects on female reproduction and hatchling phenotype. Maternal temperature affected egg-laying date, hatching success and hatchling linear size(snout-vent length, SVL) but not clutch size, egg size, egg component, and embryonic stage at laying. More specifically, females at higher temperatures laid eggs earlier than did those at low temperatures, eggs laid at 31 °C were less likely to hatch than those laid at 25 °C or 28 °C, and hatchlings from eggs laid at 31 °C were smaller in SVL. Our finding that maternal temperature(pre-ovipositional thermal condition) rather than incubation temperature(post-ovipositional thermal condition) affected hatching success indicated that embryos at early stages were more vulnerable to temperature than those at late stages. Our data provide an inference that moderate maternal temperatures enhance reproductive fitness in P. chinensis.

Analysis of bending mechanism in multi-scanning laser bending process based on plastic strain development

By using multi-pass straight-line scan strategies,a larger bending angle can be achieved.There is,however,a limited understanding of the variation in bending angle per pass during multi-pass under various process parameters.In multi-pass laser scanning,the bending angle cannot always linearly increase with scanning passes and this phenomenon can be observed mostly in low heat input.Strain hardening is the common explanation for this phenomenon.However,it could not explain why this bending angle reduction phenomenon occurs at low heat input scanning rather than at high heat input scanning.In this study,this phenomenon is discussed based on strain development in experiments and numerical simulation.The different growing mechanism of plastic strain is analyzed to reveal the effects of laser power and scanning velocity.Furthermore,the opposite bending trend that occurred at larger laser power is discussed in comparison to the plastic strain development.The study shows that relatively larger heat input below 6.7 J/mm can help to avoid the bending angle reduction phenomenon and the opposite bending trend is highly dependent on the larger laser power.For achieving the expected cumulative bending angle in multi-pass laser bending,it is recommended to decrease the scanning velocity at a relatively low laser power level while increase the scanning velocity at a high level of laser power.

Perenniality:From model plants to applications in agriculture

To compensate for their sessile nature,plants have evolved sophisticated mechanisms enabling them to adapt to ever-changing environments.One such prominent feature is the evolution of diverse life history strategies,particularly such that annuals reproduce once followed by seasonal death,while perennials live longer by cycling growth seasonally.This intrinsic phenology is primarily genetic and can be altered by environmental factors.Although evolutionary transitions between annual and perennial life history strategies are common,perennials account for most species in nature because they survive well under year-round stresses.This proportion,however,is reversed in agriculture.Hence,perennial crops promise to likewise protect and enhance the resilience of agricultural ecosystems in response to climate change.Despite significant endeavors that have been made to generate perennial crops,progress is slow because of barriers in studying perennials,and many developed species await further improvement.Recent findings in model species have illustrated that simply rewiring existing genetic networks can lead to lifestyle variation.This implies that engineering plant life history strategy can be achieved by manipulating only a few key genes.In this review,we summarize our current understanding of genetic basis of perenniality and discuss major questions and challenges that remain to be addressed.

High-elevation hypoxia impacts perinatal physiology and performance in a potential montane colonizer

Climate change is generating range shifts in many organisms,notably along the elevational gradient in mountainous environments.However,moving up in elevation exposes organisms to lower oxygen availability,which may reduce the successful reproduction and development of oviparous organisms.To test this possibility in an upwardcolonizing species,we artificially incubated developing embryos of the viperine snake(Natrix maura)using a split-clutch design,in conditions of extreme high elevation(hypoxia at 2877 m above sea level;72%sea-level equivalent O2 availability)or low elevation(control group;i.e.normoxia at 436 m above sea level).Hatching success did not differ between the two treatments.Embryos developing at extreme high elevation had higher heart rates and hatched earlier,resulting in hatchlings that were smaller in body size and slower swimmers compared to their siblings incubated at lower elevation.Furthermore,post-hatching reciprocal transplant of juveniles showed that snakes which developed at extreme high elevation,when transferred back to low elevation,did not recover full performance compared to their siblings from the low elevation incubation treatment.These results suggest that incubation at extreme high elevation,including the effects of hypoxia,will not prevent oviparous ectotherms from producing viable young,but may pose significant physiological challenges on developing offspring in ovo.These early-life performance limitations imposed by extreme high elevation could have negative consequences on adult phenotypes,including on fitness-related traits.

Natural nest substrates influence squamate embryo physiology but have little effect on hatchling phenotypes

Vertebrate embryos require access to water;however,many species nest in terrestrial habitats that vary considerably in moisture content.Oviparous,non-avian reptiles have served as models to understand how environmental factors,like moisture availability,influence development because eggs are often exposed to prevailing environments in the absence of parental care.Though much research demonstrates the importance of water absorption by eggs,many ecological factors that influence moisture availability in natural nests have received little attention.For example,the type of substrate in which nests are constructed is understudied.We experimentally incubated eggs of the brown anole lizard(Anolis sagrei)in 2 naturally occurring nest substrates that were treated with varying amounts of water to determine how natural substrates influence development at different moisture concentrations.One substrate consisted of sand and crushed seashells and the other was mostly organic material(i.e.decayed plant material).Both are common nesting substrates at our field site.When controlling for water uptake by eggs,we found that egg survival and hatchling phenotypes were similar between substrates;however,embryos developed more quickly in the sand/shell substrate than the organic substrate,indicating substrate-specific effects on embryo physiology.These results demonstrate that different natural substrates can result in similar developmental outcomes if the water available to eggs is comparable;however,some aspects of development,like developmental rate,are affected by the type of substrate,independent of water availability.Further study is required to determine how natural substrates influence embryo physiology independent of water content.