A skeletochronological estimate of age in a population of the Siberian Wood Frog, Rana amurensis, from northeastern China

I used skeletochronology to estimate age structure of the Siberian Wood Frog, Rana amurensis, from northeastern China. Average age did not differ significantly between males and females. Age at sexual maturity in both males and females was 1 year. For both sexes the maximum age observed was 4 years. Average body size differed significantly between the sexes, with males being larger than females. A significantly and positively correlation between body size and age was found within each sex in the population. When the effect of age was controlled, males also had larger size than females, suggesting that sexual selection for larger males might improve male mating success

Genomic evidence for adaptive differentiation among Microhyla fissipes populations : Implications for conservation

Aim Amphibians require both terrestrial and aquatic environments to complete their life cycles. Thus, they are subject to complex selection pressures stemming from different environments, and these selection pressures are likely to vary geographically with variation in temperature and precipitation. Studies of genetic differentiation along geographical clines allow identification of footprints of these selection pressures. Location China. Methods To identify possible signatures of local adaptation to particular environmental conditions, we conducted a genome-scan with 20,572 single-nucleotide polymorphisms (SNPs) obtained with restriction site-associated DNA sequencing of pooled samples from 10 Microhyla fissipes populations spanning a 1,398 km long latitudinal gradient in China. Results The results revealed significant genetic differentiation among populations (F-ST =0.090). Numerous outlier SNPs associated with variation in both annual average temperature (n = 69) and precipitation (n = 248) were detected. Main conclusions The degree and pattern of population differentiation in the SNPs supported the hypothesis that these SNPs have been subject to directional natural selection associated with temperature and precipitation and, hence, are reflective of geographically varying local adaptation. Hence, conservation and management plans for Microhyla fissipes should take into account this heterogeneity in genetic constitution in its populations.Peer reviewe

Sexual size dimorphism in anurans: roles of mating system and habitat types

BACKGROUND: Sexual size dimorphism (SSD) is widespread and variable among animals. Sexual selection, fecundity selection and ecological divergence between males and females are the major evolutionary forces of SSD. However, the influences of mating system and habitat types on SSD have received little attention. Here, using phylogenetic comparative methods, we at first examine the hypotheses to that mating system (intensity of sexual selection) and habitat types affect significantly variation in SSD in anurans (39 species and 18 genera). RESULTS: Our data set encompass 39 species with female-biased SSD. We provide evidence that the effects of mating system and habitat types on SSD were non-significant across species, also when the analyses were phylogenetically corrected. CONCLUSIONS: Contrast to the hypotheses, our findings suggest that mating system and habitat types do not play an important role in shaping macro-evolutionary patterns of SSD in anurans. Mating system and habitat types cannot explain the variation in SSD when correcting for phylogenetic effects

Evidence for directional testes asymmetry in <em>Hyla gongshanensis jindongensis</em>

The compensation hypothesis predicts that one testis may grow more for compensating for a reduced function in the other testis, thus exhibiting a directional asymmetry in testis size. In this study, we tested the prediction of the compensation hypothesis in the Chinese endemic Tree Frog Hyla gongshanensis jingdongensis in a population in Kegong Reserve site of Yunan Province in western China. For fifty-three male samplings, we found that the left testis size was significantly bigger than the right testis, which exhibited a significantly directional testis asymmetry, consistent with the evidence that mainly the left testis is functional with the right testis having a compensatory role, i.e. the left testis would increase in size if the right testis became non-functional. However, the relative testes size and the degree of testes asymmetry were not correlated with body condition in this species, suggesting that the testes asymmetry can not reflect male quality: high-quality individuals would not have more asymmetric testes.

Modulation of Gene Expression in Liver of Hibernating Asiatic Toads (Bufo gargarizans)

Hibernation is an effective energy conservation strategy that has been widely adopted by animals to cope with unpredictable environmental conditions. The liver, in particular, plays an important role in adaptive metabolic adjustment during hibernation. Mammalian studies have revealed that many genes involved in metabolism are differentially expressed during the hibernation period. However, the differentiation in global gene expression between active and torpid states in amphibians remains largely unknown. We analyzed gene expression in the liver of active and torpid Asiatic toads (Bufo gargarizans) using RNA-sequencing. In addition, we evaluated the differential expression of genes between females and males. A total of 1399 genes were identified as differentially expressed between active and torpid females. Of these, the expressions of 395 genes were significantly elevated in torpid females and involved genes responding to stresses, as well as contractile proteins. The expression of 1004 genes were significantly down-regulated in torpid females, most which were involved in metabolic depression and shifts in the energy utilization. Of the 715 differentially expressed genes between active and torpid males, 337 were up-regulated and 378 down-regulated. A total of 695 genes were differentially expressed between active females and males, of which 655 genes were significantly down-regulated in males. Similarly, 374 differentially expressed genes were identified between torpid females and males, with the expression of 252 genes (mostly contractile proteins) being significantly down-regulated in males. Our findings suggest that expression of many genes in the liver of B. gargarizans are down-regulated during hibernation. Furthermore, there are marked sex differences in the levels of gene expression, with females showing elevated levels of gene expression as compared to males, as well as more marked down-regulation of gene-expression in torpid males than females.Peer reviewe

Predicting Influenza Antigenicity by Matrix Completion With Antigen and Antiserum Similarity

The rapid mutation of influenza viruses especially on the two surface proteins hemagglutinin (HA) and neuraminidase (NA) has made them capable to escape from population immunity, which has become a key challenge for influenza vaccine design. Thus, it is crucial to predict influenza antigenic evolution and identify new antigenic variants in a timely manner. However, traditional experimental methods like hemagglutination inhibition (HI) assay to select vaccine strains are time and labor-intensive, while popular computational methods are less sensitive, which presents the need for more accurate algorithms. In this study, we have proposed a novel low-rank matrix completion model MCAAS to infer antigenic distances between antigens and antisera based on partially revealed antigenic distances, virus similarity based on HA protein sequences, and vaccine similarity based on vaccine strains. The model exploits the correlations of viruses and vaccines in serological tests as well as the ability of HAs from viruses and vaccine strains in inferring influenza antigenicity. We also compared the effects of comprehensive 65 amino acids substitution matrices in predicting influenza antigenicity. As a result, we applied MCAAS into H3N2 seasonal influenza virus data. Our model achieved a 10-fold cross validation root-mean-squared error (RMSE) of 0.5982, significantly outperformed existing computational methods like antigenic cartography, AntigenMap and BMCSI. We also constructed the antigenic map and studied the association between genetic and antigenic evolution of H3N2 influenza viruses. Finally, our analyses showed that homologous structure derived amino acid substitution matrix (HSDM) is most powerful in predicting influenza antigenicity, which is consistent with previous studies