Sexual Dimorphism and Female Reproductive Characteristics in the Hainan Water Skink(Tropidophorus hainanus)from Hainan,South China

We studied sexual dimorphism in body size and shape and female reproductive characteristics in the Hainan Water Skink(Tropidophorus hainanus)from Hainan,South China.In our sample the largest female and male were 61.1 and 55.2 mm snout-vent length(SVL),respectively.The mean SVL was larger in adult females(52.0 mm)than in adult males(48.3 mm).Juveniles were sexually dimorphic in head length but not in other examined morphological variables.Adult males were longer in head length and shorter in abdomen length and fore-limb length than adult females of the same SVL.Ontogenetic shifts in sexual dimorphism in body shape were evident,as revealed by the fact that morphological differences between the sexes were more pronounced in adults than in juveniles.Females produced a single litter of 3–6 offspring per season from early August to early September.Litter size,litter mass and offspring(neonate)mass were positively related to female SVL.Neonate mass was independent of relative fecundity.From the above findings we draw three main conclusions.First,females are the larger sex in T.hainanus,and sexual dimorphism in body shape is more pronounced in adults than in juveniles.Second,larger female T.hainanus produce more and larger offspring and thus heavier litters than smaller ones.Third,the offspring size-number trade-off does is not evident in T.hainanus.

Sexual Dimorphism,Female Reproductive Characteristics and Embryonic Thermosensitivity in the Tonkin Forest Skink(Sphenomorphus tonkinensis)from Hainan,South China

We collected 75 adult Tonkin forest skinks(Sphenomorphus tonkinensis) from Hainan, South China and incubated eggs at four constant temperatures ranging from 22 ℃ to 28 ℃ to study sexual dimorphism, female reproductive characteristics and embryonic thermosensitivity. The largest male was 53.4 mm snout-vent length(SVL), and the largest female was 54.3 mm SVL. The mean SVL was slightly greater in adult females(49.9 mm) than in adult males(48.8 mm), but the difference was not significant.Head length, head width, fore-limb length and hindlimb length were longer in adult males and abdomen length was longer in adult females after accounting for SVL. Accordingly, we conclude that S. tonkinensis is basically a sexually size-monomorphic species with sexual dimorphism in head size, abdomen(trunk)length and limb size. Females laid up to two clutches of 1–4 eggs each per egg-laying season from February to May. Egg mass, clutch size and clutch mass were independent of female SVL. Embryonic stages at laying varied from Dufaure and Hubert’s stage 30 to 31. With female SVL held constant, the negative correlation between egg mass and clutch size was not significant, suggesting that the offspring(egg) sizenumber trade-off between is not evident or eggs are well optimized for size in S. tonkinensis. None of the eggs at 28 ℃ hatched;hatching success was lower at 22 ℃ than at 24 ℃ or 26 ℃. The mean incubation length was 52.9 d at 22 ℃, 40.4 d at 24 ℃ and 33.6 d at 26 ℃. Hatchlings from eggs incubated at 22 ℃,24 ℃ and 26 ℃ did not differ morphologically at hatching, suggesting that temperatures within this range do not differentially affect hatchling morphology in S. tonkinensis.

Lineage Diversification and Niche Evolution in the Chinese Cobra Naja atra (Elapidae)

Theroleof nicheevolution(niche conservatism or niche divergence)in lineage diversification is a poorly studied area.The Chinese cobra Naja atra(Elapidae)has diverged into three lineages:Lineage E in eastern China,Lineage S in southern China and Vietnam,and Lineage W in western China.However,whether the ecological niche is conserved or divergent among these three lineages is unknown.In the present study,we used ecological niche models in geographical space to study the ecological differences among lineages.We compared the niche overlap in environmental space to test niche conservatism and niche divergence.Our results showed that the three lineages of N.atra shared an ecological niche space between Lineages E and S/W,with the climatic niches of Lineages S and W representing a specialized fraction of the climatic niche of Lineage E.We speculated that the niche divergence between Lineages S and W was a consequence of geographical barriers limitinggeneflow.Ourstudyprovides evidence for lineage diversification associated with both geographical isolation and climatic niche evolution,suggesting that early niche divergence between Lineages S and W,followed by niche conservatism,causes niche divergence among lineages.

Sexual size monomorphism may evolve in lizards with a body size maximizing reproductive performance for both sexes

We used Takydromus septentrionalis,a sexually size-monomorphic lacertid lizard,as a model system to test the hypothesis that sexual size monomorphism may evolve in lizards where reproductive performance is maximized at a similar body size for both sexes.We allowed lizards housed in laboratory enclosures to lay as many clutches(for females)as they could or to mate as many times(for males)as they could in a breeding season.Size-assortative mating was weak but evident in T.septentrionalis,as revealed by the fact that male and female snout–vent lengths(SVLs)in mating pairs were significantly and positively correlated.Mating frequency(indicative of male reproductive performance)varied from 1 to 8 per breeding season,generally increasing as SVL increased in adult males smaller than 67.4 mm SVL.Clutch frequency varied from 1 to 7 per breeding season,with female reproductive performance(determined by clutch frequency,annual fecundity,and annual reproductive output)maximized in females with a SVL of 68.0 mm.Accordingly to our hypothesis,the reproductive performance was maximized in the intermediate sized rather than the largest individuals in both sexes,and the body size maximizing reproductive performance was similar for both sexes.Future work could usefully investigate other lineages of lizards with sexually monomorphic species in a phylogenetic context to corroborate the hypothesis of this study.

Temperature determines the shift of thermal neutral zone and influences thermogenic capacity in striped hamsters

The thermoneutral zone(TNZ)reflects the adaptation of mammals to their natural habitat.However,it remains unclear how TNZ shifts in response to variations in ambient temperature.To test the hypothesis that ambient temperature plays a key role in determining TNZ variations between seasons,we measured metabolic rate,body temperature,and cytochrome c oxidase(COX)activity of several visceral organs in striped hamsters(Cricetulus barabensis)either acclimated to semi-natural conditions over a year,or subjected to a gradual decrease in mean temperature from 30±1°C to-15±1°C.The TNZ range in striped hamsters differed seasonally,with a wider TNZ and a lower lower-critical temperature in winter compared to summer.The hamsters showed a consider-able leftward shift of lower-critical temperature from 30°C to 20°C after the ambient temperature of acclimation from 30°C down to-15°C,whereas the upper-critical temperature of TNZ remainedfixed at 32.5°C.The rest-ing metabolic rate in thermoneutral zone(RMRt),nonshivering thermogenesis(NST),and COX activity of brown adipose tissue,liver,skeletal muscle,brain,and kidneys,increased significantly in hamsters acclimated at lower ambient temperatures.Following acute exposure to 5°C and-15°C,hamsters acclimated to 32.5°C had signifi-cantly lower maximal NST and lower serum thyroid tri-iodothyronine(T3)levels compared to those kept at 23°C.Thesefindings suggest that acclimation to the upper-critical temperature of TNZ impairs the hamsters’thermo-genic capacity to cope with extreme cold temperature.Reduced ambient temperature was mainly responsible for the leftward shift of TNZ in striped hamsters,which reflects the adaptation to cold environments.

Lectin affinity-based glycoproteome analysis of the developing xylem in poplar

Glycosylation is a significant post-translational modification of proteins,and some glycoproteins serve as players in plant cell wall synthesis and modification.Wood is a highly developed cell wall organization,and protein glycosylation as a regulatory mechanism may be involved in wood formation.Here,a lectin affinity-based glycoproteome was performed in stem developing xylem of poplar.After enrichment,trypsin digestion,LC-MS/MS analysis and peptide identification,we identified 154 glycoproteins from poplar developing xylem,which were classified into nine functional groups mainly including protein acting on carbohydrates,oxido-reductase,proteases,and protein kinases.Further,N-and/or Oglycosylation sites of the identified proteins were analyzed using bioinformatic tools,and deglycosylation experiments in the selected PtSOD and PtHAD proteins verified the reliability of the identified glycoproteins.Analysis of protein subcellular localization showed that a total of 63%of the identified glycoproteins were extracellular proteins or located in the plasma membrane.Poplar eFP and RT-qPCR data showed that a number of the genes encoding these glycoproteins such as laccase,peroxidase and cysteine protease,have highly preferential expression profiles in the developing xylem.Together with previously published research,most identified glycoproteins could be involved in wood cell wall synthesis and modification in poplar.Thus,our study provides some potential wood formation-related glycoproteins to be determined during tree stem development.

Genetic and epigenetic regulators of retinal Müller glial cell reprogramming

Background:Retinal diseases characterized with irreversible loss of retinal nerve cells,such as optic atrophy and retinal degeneration,are the main causes of blindness.Current treatments for these diseases are very limited.An emerging treatment strategy is to induce the reprogramming of Müller glial cells to generate new retinal nerve cells,which could potentially restore vision.Main text:Müller glial cells are the predominant glial cells in retinae and play multiple roles to maintain retinal homeostasis.In lower vertebrates,such as in zebrafish,Müller glial cells can undergo cell reprogramming to regenerate new retinal neurons in response to various damage factors,while in mammals,this ability is limited.Interestingly,with proper treatments,Müller glial cells can display the potential for regeneration of retinal neurons in mammalian retinae.Recent studies have revealed that dozens of genetic and epigenetic regulators play a vital role in inducing the reprogramming of Müller glial cells in vivo.This review summarizes these critical regulators for Müller glial cell reprogramming and highlights their differences between zebrafish and mammals.Conclusions:A number of factors have been identified as the important regulators in Müller glial cell reprogramming.The early response of Müller glial cells upon acute retinal injury,such as the regulation in the exit from quiescent state,the initiation of reactive gliosis,and the re-entry of cell cycle of Müller glial cells,displays significant difference between mouse and zebrafish,which may be mediated by the diverse regulation of Notch and TGFβ(transforming growth factor-β)isoforms and different chromatin accessibility.

The functional significance of residual yolk in lizards

Residual yolk is assumed to be an important source of energy and nutrients during early life in nonmammalian amniotes.Available data show that the mean size of residual yolk is far smaller in lizards than in turtles,snakes,crocodiles,and birds,raising a question of whether residual yolk is of functional significance in lizards.Here,we compared data from 26 lizard species with those from other nonmammalian amniotes to test the hypothesis that residual yolk is functionally less significant in species producing more fully developed offspring.In our sample,species mean offspring water contents ranged from 73%to 84%of body wet mass;species mean proportions of carcass dry mass,fat-body dry mass,and residual yolk dry mass to offspring dry mass ranged from 84%to 99%,0%to 5.0%,and 0%to 14.4%,respectively.Lizards are,on average,more fully developed at hatching or birth than snakes,as revealed by the fact that the mean proportion of carcass dry mass to body dry mass and offspring water contents were both higher in lizards than in snakes.We conclude that the functional significance of residual yolk during early life is generally less evident in lizards.Even in the lizards where residual yolk is of potential functional significance,this portion of yolk contributes little,if any,to postembryonic growth.Future work could usefully collect data across a wider spectrum of reptile taxa to establish a precocial-altricial continuum and test the hypothesis that species with a smaller amount of residual yolk are closer to the precocial end of the continuum.