Genetic mechanism of body size variation in groupers:Insights from phylotranscriptomics

Animal body size variation is of particular interest in evolutionary biology,but the genetic basis remains largely unknown.Previous studies have shown the presence of two parallel evolutionary genetic clusters within the fish genus Epinephelus with evident divergence in body size,providing an excellent opportunity to investigate the genetic basis of body size variation in vertebrates.Herein,we performed phylotranscriptomic analysis and reconstructed the phylogeny of 13 epinephelids originating from the South China Sea.Two genetic clades with an estimated divergence time of approximately 15.4 million years ago were correlated with large and small body size,respectively.A total of 180 rapidly evolving genes and two positively selected genes were identified between the two groups.Functional enrichment analyses of these candidate genes revealed distinct enrichment categories between the two groups.These pathways and genes may play important roles in body size variation in groupers through complex regulatory networks.Based on our results,we speculate that the ancestors of the two divergent groups of groupers may have adapted to different environments through habitat selection,leading to genetic variations in metabolic patterns,organ development,and lifespan,resulting in body size divergence between the two locally adapted populations.These findings provide important insights into the genetic mechanisms underlying body size variation in groupers and species differentiation.

Differences in Thermal Preference and Tolerance among Three Phrynocephalus Lizards (Agamidae) with Different Body Sizes and Habitat Use

We acclimated adults of two viviparous （Phrynocephalus guinanens＆ and P. vlangalii） and one oviparous （P. versicolor） species of toad-headed lizards （Agamidae） to 28 ℃, 33 ℃ and 38 ℃ to examine whether thermal preference （preferred body temperature, Tp） and thermal tolerance （critical thermal minimum, CTMin; critical thermal maximum, CTMax） were affected by acclimation temperature, and correlate with body size and habitat use. Both Tp and CTMax were highest in P. versicolor and lowest in P. vlangalii, with P. guinanensis in between. The two viviparous species did not differ in CTMin and thermal tolerance range, and they both were more resistant to low temperatures and had a wider range of thermal tolerance than the oviparous species. Both CTMin and CTMax shifted upward as acclimation temperature increased in all the three species. Tp was higher in the lizards acclimated to 33 ℃ than in those to 28 ℃ or 38 ℃. The range of thermal tolerance was wider in the lizards acclimated to 28 ℃ than in those to 33 ℃ or 38 ℃. The data showed that： 1） thermal preference and tolerance were affected by acclimation temperature, and differed among the three species of Phrynocephalus lizards with different body sizes and habitat uses; 2） both Tp and CTMax were higher in the species exchanging heat more rapidly with the environment, and CTMin was higher in the species using warmer habitats during the active season; and 3） thermal preference and tolerance might correlat with body size and habitat use in Phrynocephalus lizards.

Factors determining the average body size of geographically separated Arctodiaptomus salinus （Daday, 1885） populations

Arctodiaptomus salinus inhabits water bodies across Eurasia and North Africa. Based on our own data and that from the literature, we analyzed the influences of several factors on the intra- and inter-population variability of this species. A strong negative linear correlation between temperature and average body size in the Crimean and African populations was found, in which the parameters might be influenced by salinity. Meanwhile, a significant negative correlation between female body size and the altitude of habitats was found by comparing body size in populations from different regions. Individuals from environments with highly varying abiotic parameters, e.g. temporary reservoirs, had a larger body size than individuals from permanent water bodies. The changes in average body mass in populations were at 11.4 times, whereas, those in individual metabolic activities were at 6.2 times. Moreover, two size groups of A. salinus in the Crimean and the Siberian lakes were observed. The ratio of female length to male length fluctuated between 1.02 and 1.30. The average size of A. salinus in populations and its variations were determined by both genetic and environmental factors. However, the parities of these factors were unequal in either spatial or temporal scales.

Effects of Body Size and Environmental Factors on the Acoustic Structure and Temporal Rhythm of Calls in Rhacophorus dennysi

In anurans, the outcomes of male-male contests and female choice are often associated with body size. In some species, males evaluate an opponent’s fighting ability and females evaluate male quality on the basis of male communication signals, which are thought to reflect information concerning male body size. Nevertheless, previous studies reveal that male call structure is not always correlated with body size. In the present study we investigated the relationships between body size and call structure in the large treefrog, Rhacophorus dennysi, as well as the relationship of its calling behavior with air temperature and humidity. The results show that both the dominant and fundamental frequencies are negatively correlated with body size, while inter-note intervals are positively correlated with body size, indicating that call characters could reflect body size in this species.Additionally, calling in this tropical species exhibits a circadian rhythm insofar as relatively high temperature and low humidity during the day is associated with less vocal behavior. Thus, individual variations in call structure are mainly dependent on body size while the temporal rhythm of calling activity is affected by environmental conditions in large treefrogs.

Heritability of resistance-related gene expression traits and their correlation with body size of clam Meretrix petechialis

Gene expression variation can be considered as a phenotype,and it plays an important role in both acclimation and adaption.However,genetic variation of gene expression received much less attention than traditional commercial traits in aquaculture.To estimate the genetic variation and heritability of gene transcription in clam Meretrix petechialis,five Vibrio resistance-related genes were selected for gene expression analysis in the digestive gland,and an animal linear model was used to analyze data from quantitative real-time PCR(qRT-PCR).Among the five genes,BIRC7 showed significant additive genetic variations,the heritability of this gene of 12-month-and 15-month-old clams were 0.84±0.32 and 0.91±0.34,respectively.The heritability of other four genes(Bax,NFIL3,Big-Def,and CTL9)expression were low-tomoderate but not significantly expressed.Additionally,no significant phenotypic and genetic correlations between the BIRC7 transcription trait and body size were detected.This study highlights that certain gene expression variation is heritable and provides a reference for indirect selection of M.petechialis with high Vibrio resistance.

No Evidence for Significant Effect of Body Size and Age on Male Mating Success in the Spot-legged Treefrog

In anurans, body size and age of individuals generally affect male mating success. To test whether body size and age have effects on male mating success in the foam-nesting treefrog Polypedates megacephalus, a species widely distributed in China, we analyzed differences in body size and age between mated and unmated males for three populations using a Generalized Linear Mixed Model（GLMM）. The results showed that mated males did not exhibit larger body size and older age than unmated males, suggesting that large and/or old male individuals did not have greater mating success than small and/or young males. Moreover, we also found a non-significant size-assortative mating pattern for all populations. Our findings suggest that body size and age of the foam-nesting treefrog do not affect male mating success.

Nonlinear Phenomena Conveying Body Size Information and Improving Attractiveness of the Courtship Calls in the Males of Odorrana tormota

Nonlinear phenomena are commonly shown in the vocalization of animals and exerts different adaptive functions.Although some studies have pointed out that nonlinear phenomena can enhance the individual identification of male Odorrana tormota,whether the nonlinear phenomena play a specific role in the sexual selection of O.tormota remain unclear.Here we presented evidence that there was a significant negative correlation(Pearson:n=30,r=0.65,P<0.001)between the nonlinear phenomena content and snout-vent length in the male O.tormota,and two-choice amplexus experiments showed that female O.tormota preferred male with smaller body size containing higher nonlinear phenomena content in its calls.Phonotaxis experiments also revealed that females preferred calls with higher nonlinear phenomena content.Additionally,compared to the calls with lower nonlinear phenomena content and higher fundamental frequency,there was shorter response time in phonotactic behaviour of female induced by the calls with higher nonlinear phenomena content and lower fundamental frequency.We argue that the nonlinear phenomena content in the calls of male O.tormota can convey its body size information and may provide important clues for female frogs in darkened surroundings to identify males’body size during mate choice,meanwhile,higher nonlinear phenomena content in males’calls may increase the attractiveness of males to females.The results of this study provide confirmation that,for O.tormota,nonlinear phenomena have specific function in mate choice.

Body Size and Reproductive Tactics in Varanid lizards

Body size and female reproduction in the water adult females larger than 500 mm SVL and 32 adult males Ledong, Hainan under permit to our laboratory in Hainan monitor lizard （Varanus salvator） were studied. Forty-two larger than 400 mm SVL were donated by local people in in 2013 and 2014. The largest male and female measured 745 and 755 mm SVL, respectively. The mean SVL was greater in adult females than in adult males. Males had larger heads （head width） than females of the same SVL. The smallest reproductive female in our sample was 565 mm SVL. Females produced a single clutch of 17.1 （10-23） pliable-shelled eggs per breeding season stretching from mid-June and mid-September. Clutch size and clutch mass were all positively related to female SVL. However, there was no significant linear relationship between egg mass and female SVL. Larger females generally produced more eggs, and thus heavier clutches than did smaller ones. There was no significant linear relationship between relative clutch mass and female SVL. Phylogenetic generalized least squares （PGLS） analysis, accounting for phylogenetic relationships, showed that clutch size was positively correlated with mean maternal SVL in varanid lizards. PGLS analysis showed that phylogenetic relationships did not affect clutch （or/and egg） mass and the SVL although there were significant linear relationship between clutch （or/and egg） mass and mean maternal SVL. Therefore, we could draw some general conclusions about the body size and reproductive tactics in varanid lizards that larger females generally produced more eggs, larger eggs and thus heavier clutches than did smaller ones.

Variation and Sexual Dimorphism of Body Size in the Plateau Brown Frog along an Altitudinal Gradient

Variation in body size and sexual size dimorphism（SSD） can have important consequences for animal ecology, behavior, population dynamics and the evolution of life-history traits. Organisms are expected to be larger in colder climate（i.e., Bergmann＇s rule） and SSD varies with body size（i.e., Rensch＇s rule）. However, the underlying mechanisms are still elusive. The plateau brown frog（Rana kukunoris）, a medium-sized anuran species with femalebiased SSD, is endemic to the Qinghai-Tibetan Plateau（QTP）. From 1797 m（Maoxiang＇ping） to 3453 m（Heihe＇qiao） in the eastern margin of the QTP, we surveyed 10 populations of R. kukunoris and collected phalanges and snout vent length（SVL） data for 258 adult individuals（199 males versus 59 females）. Based on these data, we explored how body size and SSD varying along the altitudinal gradient and examined the corresponding effects of temperature. We found body size to be larger at higher altitude for males but not for females, with likely effects from the temperature on the variation in male body size. Sex differences in growth rates may be the main cause of the variation in SSD. Our results suggested that only males follow the Bergmann＇s rule and variation in SSD of R. kukunoris do not support the Rensch＇s rule and its inverse. Therefore, the variations of body size can be different between sexes and the applicability of both Bergmann＇s rule and Rensch＇s rule should depend on species and environment where they live.

Correlation Study on Body Size,Sexual Behavior and Semen Quality of Dezhou Donkey

[ Objective] The study was to explore whether the body size, sexual behavior of male donkey had certain correlation with reproductive traits. [ Method] The data of body weight, body size and sexual behavior of male donkey during production were collected, combining with the semen quality data of ejaculation volume, density, motility and frozen-thawed semen motility were conducted the statistical analysis. [ Results] （ 1 ） Single ejaculation volume had a positive correlation with body height （r = 0. 423, P = 0. 044） and penis circumference （r = 0. 495, P = 0. 043 ） , and total number of sperm per ejaculate had a positiw： correlation with body weight （r = 0. 444, P = 0. 036） and scrotal circumference （r = 0. 520, P = 0. 039） ; （2） Ejaculation volume was negatively correlated with mount times （r = -0. 159, P = 0. 035） and erection time （r = -0. 181, P = 0. 023）, semen density was negatively correlated with mating time （r = - 0.211, P = 0.004）, and total sperm count was negatively correlated with erection time （r = - 0. 159 , P = 0. 047）. [Condusion ] The quality of semen had a certain correlation with body size, body weight and sexual behavior.

Correlation Analysis between Body Size and Slaughter Performance in F-_1 Hybrid Offspring of Princess Chicken and Kirin Chicken

In order to study the meat development value of princess chicken,the body size traits and slaughter performance of 12-week-old F1 hybrid offspring of princess chicken(♂) and kirin chicken(♀) were measured and the correlations between different traits were analyzed. The results showed that body length,keel length and shank length of male F1 hybrid offspring were significantly higher than those of female chickens(P 【 0. 05). The live weight,carcass weight,semi-eviscerated weight,semi-eviscerated ratio,eviscerated weight,chest muscle weight,the leg muscle weight and heart weight of male chickens were extremely significantly higher than that of female chickens(P 【 0. 01),and the leg muscle ratio and wings weight were significantly higher than that of female chickens(P 【 0. 05),but sebum thickness of male chickens was extremely significantly lower than that of female chickens(P 【 0. 01). Other indicators failed to reach the significant difference level. There were extremely significant or significant correlations between the slaughter performance and body size in F1 hybrid offspring. The regression equations between different indicators were identified and developed. The results provided a certain theoretical reference to predict slaughter performance indicators through a living body size measurement,and revealed an improved production performance of F1 hybrid offspring.

Body size structure of Pleistocene mammalian communities: what support is there for the “island rule”?

Islands are often regarded by scientists as living laboratories of evolution and an optimal context for the study of forces influencing evolution and diversification.Two main issues have been attentively scrutinized and debated:the loss of biodiversity and the peculiar changes undergone by island settlers,primarily changes in size of endemic vertebrates.Over time,several hypotheses have been formulated to explain the causal mechanism of body size modification.Faunas of those islands where mainland taxa migrate more than once provide the most interesting data to answer the question of whether or not trends of insular taxa result from a predictable response to differences in competition and availability of niches between insular and mainland environments.To contribute to the debate,the body size structure of the Pleistocene mammalian faunas from two Mediterranean islands,Sicily and Crete,were analyzed and compared with the structure of coeval mainland faunas.The results obtained suggest that:(i)size of endemic species does not directly depend on the area of islands;(ii)evolution and size of endemic species seems somewhat affected by the degree of isolation(constraining coloniza-tion from mainland)and physiography(sometimes permitting adaptive radiation);(iii)in unbalanced insular communities,the shift in size of non-carnivorous species largely depends on the nature of competing species;and(iv)body size of carnivorous species mainly depends on the size of the most available prey.Consequently,it is rational to suppose that the body size of insular mammals mainly results from the peculiar biological dynamics that characterizes unbalanced insular communities.Ecological interaction,particularly the intraguild competition,is the major driver behind the evolution of insular communities,leading towards an optimization of energy balance through a change in body size of endemic settlers.

Comparative population genomics reveals genetic basis underlying body size of domestic chickens

Body size is the most important economic trait for animal production and breeding.Several hundreds of loci have been reported to be associated with growth trait and body weight in chickens.The loci are mapped to large genomic regions due to the low density and limited number of genetic markers in previous studies.Herein,we employed comparative population genomics to identify genetic basis underlying the small body size of Yuanbao chicken(a famous ornamental chicken)based on 89 whole genomes.The most significant signal was mapped to the BMP10 gene,whose expression was upregulated in the Yuanbao chicken.Overexpression of BMP10 induced a significant decrease in body length by inhibiting angiogenic vessel development in zebrafish.In addition,three other loci on chromosomes 1,2,and 24 were also identified to be potentially involved in the development of body size.Our results provide a paradigm shift in identification of novel loci controlling body size variation,availing a fast and efficient strategy.These loci,particularly BMP10,add insights into ongoing research of the evolution of body size under artificial selection and have important implications for future chicken breeding.

Changes in diversity and body size of Onychiurinae(Collembola:Onychiuridae)along an altitudinal gradient in Changbai Mountain,China

Collembola are among the most abundant and diverse soil animals contributing significantly to major ecosystem processes.Global climate changes in temperature and precipitation are likely to affect their community structure and functioning and this is likely to differ along altitudinal gradients.In this study,changes in richness,abundance,and body size of onychiurin Collembola with altitude have been investigated in the Changbai Mountain range of northeast China.Sampling was carried out on a 30 km long transect along forested slopes of the Changbai Mountains.Standardized samples were taken from 800 to 1700 m at seven altitudinal levels.More than 5000 specimens of Onychiurinae representing 13 species were collected,making Onychiuridae(with the sole subfamily Onychiurinae in Changbai)the most abundant Collembolan family in the area.The number of species of Onychiurinae slightly increased along the altitudinal gradient.The average number of species per sample,but not the total abundance,changed significantly but not monotonically with altitude.Body size of Onychiurinae species decreased significantly with increasing altitude contradicting Bergmann’s rule.Furthermore,the abundance of the three body-size groups differentially responded to increasing altitude,with the abundance of the large body-size group decreasing and the abundance of the small body-size group increasing.Our results suggest that the distribution patterns of Collembola along the altitudinal gradient are complicated and may be linked to taxonomic groups and bioclimatic zones.

Ecdysone and Insulin Signaling Play Essential Roles in Readjusting the Altered Body Size Caused by the dGPAT4 Mutation in Drosophila

Body size is one of the features that distinguish one species from another in the biological world. Animals have developed mechanisms to control their body size during normal development. However, how animals cope with genetic alterations and/or environmental stresses to develop into normal-sized adults remain poorly understood. The ability of the animals to develop into a normal-sized adult after the challenges of genetic alterations and/or environmental stresses reveals a robustness of body size control. Here we show that the mutation of dGPAT4, a de novo synthase of lysophosphatidic acid, is a genetic alteration that triggers such a robust response of the animals to body size challenges in Drosophila. Loss of dGPAT4 leads to a severe delay of development, slow growth and resultant small-sized animals during the larval stages, but results in normal-sized adult flies. The robust body size adjustment of the dGPAT4 mutant is likely achieved by corresponding changes in ecdysone and insulin signaling, which is also manifested by compromised food intake. Thus, we propose that a strategy has been evolved by the animals to reach final body size when challenged by genetic alterations, which requires the coordinated ecdysone and insulin signaling.

Ambient temperature alters body size and gut microbiota of Xenopus tropicalis

Temperature is important to determine physiological status of ectotherms. However, it is still not fully understood how amphibians and their symbiotic microbiota acclimate to ambient temperature. In this study, we investigated the changes of gut microbiota of Xenopus tropicalis at different temperatures under controlled laboratory conditions. The results showed that microbial communities were distinct and shared only a small overlap among froglet guts, culture water and food samples.Furthermore, the dominant taxa harbored in the gut exhibited low relative abundance in water and food. It indicates that bacterial taxa selected by amphibian gut were generally of low abundance in the external environment. Temperature could affect betadiversity of gut microbiota in terms of phylogenetic distance, but it did not affect alpha diversity. The composition of gut microbiota was similar in warm and cool treatments. However, signature taxa in different temperature environments were identified. The relationships between temperature, gut microbiota and morphology traits of X. tropicalis revealed in this study help us to predict the consequences of environmental changes on ectothermic animals.

Ambient temperature correlates with geographic variation in body size of least horseshoe bats

Geographic variation in body size is common within many animal species.The causes of this pattern,however,remain largely unexplored in most vertebrate groups.Bats are widely distributed globally owing to their ability of powered flight.Most bat species encounter a variety of climatic conditions across their distribution range,making them an ideal taxon for the study of ecogeographic patterns in body size.Here,we used adult least horseshoe bats,Rhinolophus pusillus,to test whether geographic variation in body size was determined by heat conservation,heat dissipation,climatic seasonality,or primary productivity.We measured body mass and head-body length for 246 adult bats from 12 allopatric colonies in China.We quantified the ecological conditions inhabited by each colony,including mean maximum temperature of the warmest month,mean minimum temperature of the coldest month,temperature seasonality,precipitation seasonality,and annual net primary productivity(ANPP).Body mass and head-body length,2 of the most reliable indicators of body size,exhibited marked differences between colonies.After controlling for spatial autocorrelation,the mean minimum temperature of the coldest month explained most of the variation in body size among colonies,regardless of sex.The mean maximum temperature,climatic seasonality,and ANPP had limited power in predicting body size of males or females in comparison with mean minimum temperature.These results support the heat conservation hypothesis and suggest adaptive responses of body size to cold climates in cave-dwelling bats.

Body size variation of four latitudinally-separated populations of a toad species:age and growth rate as the proximate determinants

Age and growth rate are critical parameters determining the body size of adult anurans,which grow indeterminately.Therefore,evaluating their relative importance and selective pressures acting on them may help to explain variation in body size of anurans across geographical populations.Based on the data on body size and skeletochronological age of 4 Asiatic toad(Bufo gargarizans)populations that are widely separated in latitude,the present study showed that toads at the northern extremity of the range were the oldest,on average,and grew relatively fast,toads at the southern end of the range were relatively old but grew fastest,whereas mid-latitude toads were intermediate in both traits.These results indicated that relative contributions of age and growth rate to body size differed among populations.From a life history perspective,greater age attained by toads at higher latitudes should result from delayed maturation,and faster growth from an adaptive response to strong seasonal time constraints;in contrast,selective pressures on the 2 parameters at lower latitudes might be associated,respectively,with low adult death rates and longer favorable growing seasons.

Morphological characteristics of blood cells in monitor lizards:is erythrocyte size linked to actual body size?

Blood cell morphology and count are not uniform across species.Recently,between-species comparisons revealed that the size of red blood cells is associated with body size in some lizard taxa,and this finding was interpreted in the context of the metabolic theory.In the present study,we examined the numbers and the size of blood cells in 2 species of monitor lizards,the mangrove-dwelling monitor(Varanus indicus)and the savannah monitor(V.exanthematicus),and we compared these traits in individuals of different body size.The results revealed that during the course of ontogeny,the size of red blood cells increases with body mass.Because the mass-specific metabolic rate decreases with body size and the cell volume-to-surface ratio decreases with the cell size,changes in the erythrocyte size might be the result of oxygen transport adjustment.

Genes for sexual body size dimorphism in hybrid tilapia(Oreochromis sp.x Oreochromis mossambicus)

Tilapias are important aquaculture species.Male-biased sexual size dimorphism is very common and males are preferred for aquaculture in tilapia.However,the mechanisms underlying sexual dimorphism remain to be elucidated.One hundred and thirty-six sex-biased genes,of which 23 were male-biased and 113 were femalebiased,were identified via reanalysis of a muscle transcriptome data using the latest reference genome assembly.These genes were mapped to KEGG pathways that are related to somatic cell metabolism,growth and differentiations,such as MAPK,FoxO4 and metabolism pathways as well as developmental processes responsible for skeletal muscle development.Pathways related to cell growth and proliferations such as MAPK signaling pathways are upregulated in males while pathways regulating cell division such as FoxO4 are upregulated in females.Sex-biased genes in tilapia skeletal muscle have higher evolution rates(dN/dS)compared to unbiased genes.Female-biased and male-biased genes showed 17.4%and 13.5%higher dN/dS,respectively,compared to unbiased genes.Our results suggest that some of the male and female sex-biased genes were under selection pressures.Three SNPs located in the promoter region of one sex-biased gene RASGRF1 on LG1 were associated with bodyweight differences in the hybrid tilapia.These sex-biased genes identified in this study may serve as candidate genes for future functional analysis on sexual size dimorphism and for developing DNA markers for selecting fast-growing saline tilapia in aquaculture.