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.

Flower development and sexual dimorphism in Vernicia montana

The mu oil tree(Vernicia montana Lour.) is a dioecious species, but the genetic mechanisms underlying its phenotypic sexual dimorphism are unclear. In this study, we determined two pivotal phases of sex differentiation of mu oil tree via morphological and histological analyses of unisexual flowers:(Ⅰ) differentiation of male or female primordia to produce staminate flowers(SFs) or transient hermaphrodite flowers(HFs),and(Ⅱ) complete abortion of stamens in transient HFs to generate pistillate flowers(PFs). A total of 1621 sex-biased genes were identified by comparative transcriptome analysis which exhibited elevated rates of protein evolution than unbiased genes. The female-biased genes were enriched in the production of defense compounds while male-biased genes were focused on the production of viable pollens. Transcriptomebased analysis revealed that the differentially expressed genes(DEGs) between PFs and SFs in phase Ⅰ involved in abscisic acid(ABA), auxin(AUX), cytokinin(CK), ethylene(ET), and gibberellin(GA) biosynthesis and signaling showed higher expression levels in males than in females in general, whereas the DEGs involved in jasmonic acid(JA) and salicylic acid(SA) pathways displayed opposite expression patterns. Moreover,differentially expressed endogenous ABA, AUX, GAs, JA, and SA exhibited consistent biased expression patterns with the DEGs by UPLC-MSbased analysis. Exogenous application of an anti-ethylene plant growth regulator could promote the development of stamens in PFs and generated HFs. Comparative transcriptomic and hormonal analyses of PFs and SFs in phase Ⅱ indicated an increase in ET concentration when abortion of stamens in PFs occurred. This study suggested that phytohormones play key roles in sex dimorphism and ET may determine the development of stamens in PFs of mu oil tree, which provides an insight into plant sex differentiation mechanisms.

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.

Body Size but Not Food Size Determined Head Sexual Dimorphism in Rana kukunoris from the Tibetan Plateau

Sexual dimorphism between males and females is a common pattern observed in the natural world and has become one of the main focuses of evolutionary biology.Amphibian head size and shape are important factors that may influence food acquisition,but knowledge about the sexual differences between amphibian head size and shape is relatively scant.Here,intersexual differences in the head size and shape of Rana kukunoris,which is a high-elevation frog from the Qinghai-Tibet Plateau,were investigated.Significant differences were found in the head shape but not the head size between sexes.A significant correlation was also observed between prey size and head size.However,these correlations disappeared when individual body size was controlled,suggesting that body size but not food size was the main factor resulting in intersexual differences in head size/shape.The results suggested that food competition between sexes did not result in sexual dimorphism of head shape among these frogs.

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet-Dagh Basin,NE Iran

Spatangoid echinoids belonging to Heteraster found in the Lower Cretaceous limestones and calcareous deposits of the Tirgan and Sarcheshmeh formations(Barremian-Aptian)in the Bahman jan-Bala stratigraphic section on the northern flank of the Borouj syncline,situated in the eastern Kopet-Dagh Basin,northeastern Iran are assessed as a sexually dimorphic species.Sexual dimorphism is a common feature in echinoids and,in this study of Heteraster renngarteni Poretzkaja,1961,sexual dimorphism has been detected for the first time in the family Toxasteridae.

Inverse of Rensch’s Rule of Allometry for Sexual Size Dimorphism in Bufo andrewsi

Difference in body size between males and females(sexual size dimorphism:SSD)and its variation are a common phenomenon in animal kingdom.Rensch’s rule predicts that the degree of SSD variation increases with the enlarged mean body size when males are larger than females and decreases when females are larger than males.Here,whether the patterns of variations in SSD in the Andrew’s toad(Bufo andrewsi)follow Rensch’s rule was tested using unpublished data from 14 populations and published data from 17 populations.Results show the reduced major axis regression of log10(male size)on log10(female size)across all populations displayed a significant hyperallometric relationship,which was consistent with inverse Rensch’s rule(the degree of SSD increased with enlarged mean body size).SSD could also be explained by sexual age difference(SAD)due to a positive SSD–SAD relationship among all populations.The findings suggest that the occurrence of inverse Rensch’s rule in B.andrewsi is likely to be a result of fecundity selection on increased reproductive investments in larger females.

Ontogeny of Psychomotor and Sensory Functions in the Rat: Effects of Sexual Dimorphism

Background: We studied the development of eight (8) different psychomotor and sensory functions in male and female rats, from postnatal day 10 to 45, with the aim of determining whether the ontogenesis of these functions was subject to sexual dimorphism. Methods: Wistar rats bred according to standard conditions in our laboratories were put into reproduction. Ten days after whelping, male and female pups were identified and subjected to a battery of behavioral tests on postnatal days 10, 15, 20, 25, 30 and 45, to assess the development of the following psychomotor and sensory functions: Exploratory activity, locomotor activity, emotional defecation, hind paws lifting reflex latency, wire-grasping time, Latencies of execution of crawling along the wire and of leap onto the ground, nociception (tail flick) and body weight. Results: Only complex brain functions generated by cerebral cortex activities, i.e. exploratory activity and leap execution latency, do not undergo differential development sex-dependent. However, voluntary motor functions initiated in the motor cortex, and requiring high peripheral muscle performance such as crawling execution latency and wire-grasping time developed more rapidly in males than in females. Correlatively, body weight i.e. muscle mass index increased more speedily in males than in females. On the other hand, studies of automatic motor functions such as locomotor activity, and reflex motor functions i.e. hind paws lifting reflex latency and tail flick latency showed earlier development in females than in males. In addition, the study of emotional response, an emanation of limbic structures, showed prodigious development in females compared to males. Conclusion: Our studies have shown that there is a developmental sexual dimorphism of the central nervous system in the rat. Indeed, studies of automatic and reflex motor functions, whose activities are essentially linked to the spinal cord and brainstem, indicated that hindbrain areas develop more speedily in females than in males. Likewise, study of the emotional response emanating from diencephalic limbic structures, in particular the hypothalamus, showed a prodigious and early development in females compared to males. Taken together, our studies indicate that the vast majority of brain structures and functions reached maturation earlier in females than in males. Estrogen is the trigger hormone for early maturation of the female brain.

Subtle sexual plumage color dimorphism and size dimorphism in a South American colonial breeder, the Monk Parakeet(Myiopsitta monachus)

Background:Parrots(Psittacidae Family)are one of the most colorful groups of birds in the world,their colors pro-duced both structurally and via unusual pigments(psittacofulvins).Most species are considered to be monogamous,and many have been viewed historically as sexually monomorphic and monochromatic.However,studies using morphometric analysis and spectrophotometric techniques have revealed sexual size dimorphism and also sexual plumage color dimorphism among some species.The Monk Parakeet(Myiopsitta monachus),a native parrot of South America,is an interesting species for the study of plumage coloration and size since it is considered sexually mono-chromatic and monomorphic.Furthermore,recent studies show that the Monk Parakeet has extra-bond paternity behavior and even breeding trios,which suggests that sexual selection may play an important role in this species,and that it might have sexually dimorphic plumage(albeit imperceptible by humans)and be dimorphic in size.Methods:For the determination of plumage color we used spectrophotometry in the range of avian vision(300-700 nm)and performed a morphological analysis.Results:Our spectrophotometric results indicate that the Monk Parakeet shows subtle sexual plumage color dimor-phism in three(crown,nape and wing)out of twelve body regions.Similarly,our morphometric analysis showed that there are subtle sex differences in body size(bill and weight).Conclusions:Although the Monk Parakeet shows extra-bond paternity and breeding trio behaviors which could increase sexual dimorphism,these behaviors occur among highly related individuals;perhaps the high rate of inbreeding is responsible for the attenuation of sexual plumage color dimorphism and sex differences in body size observed.

Reexamination of Sexual Dimorphism and Female Reproduction in the Many-Lined Sun Skink Eutropis multifasciata from China

We reexamined sexual dimorphism and female reproduction in the Many-Lined Sun Skink Eutropis multifasciata from Hainan,China. Our data confirm that adults are sexually dimorphic in body size and shape,with males being the larger sex and larger in head size but shorter in abdomen length than females of the same snoutvent length(SVL). The rate at which head width increased with SVL was greater in males as opposed to the previous conclusion that the rate does not differ between the sexes. Maternal size was the main determinant of reproductive investment,with larger females generally producing more,as well as larger,offspring. Females produced up to nine offspring per litter as opposed to the previously reported 2–7. Most females gave birth between March and August,a time period approximately four months longer than that(May–June) reported previously. Females with a higher fecundity tended to produce smaller offspring as opposed to the previous conclusion that females do not tradeoff offspring size against number. Litter size,neonate mass and litter mass remained remarkably constant among years,and litter mass was more tightly related to female body size than litter size or neonate mass. Smaller females could produce relatively heavier litters without a concomitant reduction in postpartum body condition.

Sexual Dimorphism, Female Reproductive Characteristics and Egg Incubation in an Oviparous Forest Skink(Sphenomorphus incognitus) from South China

We studied sexual dimorphism and female reproduction in an oviparous forest skink （Sphenomorphus incognitus） from South China. We incubated eggs under five thermal regimes （22, 25, 28, 25 ± 3 and 27± 5℃） to examine the effects of constant versus fluctuating temperatures on incubation length and hatchling morphology. In our sample the largest male and female were 110 mm and 108 mm snout-vent length （SVL）, respectively. Adult males and females did not differ in mean SVL; adult males were larger in head size （both length and width）, longer in fore- and hind-limb lengths and shorter in abdomen length than females of the same SVL. Accordingly, we conclude that S. incognitus is a sexually monomorphic species in terms of SVL but shows sexual dimorphism in head size, abdomen length and appendage length. Females laid a single clutch of 3-10 eggs per breeding season from early May to mid- August, with larger females generally laying more （but not always larger） eggs per clutch than did smaller ones. Embryonic stages at laying ranged from Dufaure and Hubert＇s （1961） stage 31 to 32, with a mean stage of 31.3. The positive relationship between clutch mass and female SVL was not significant. The offspring size-number trade-off does not exist in S, incognitus, as revealed by the fact that egg mass was independent of relative fecundity. Incubation length decreased as temperature increased, and stable temperatures resulted in delayed hatching. Hatchlings incubated under the five thermal regimes did not differ from each other in any examined trait, suggesting that S. incognitus is among oviparous reptilian species where incubation temperature has no role in modifying hatchling morphology as long as eggs are not exposed to extreme temperatures for prolonged periods of time.

Sexual Dimorphism of Head Size in Phrynocephalus przewalskii: Testing the Food Niche Divergence Hypothesis

Sexual size dimorphism （SSD） is a general phenomenon in lizards, and can evolve through sexual selection or natural selection. But natural selection, which was thought to operate mainly through reducing the competition be- tween the two sexes （niche divergence hypothesis）, gave rise to a lot of controversy. We tested the niche divergence hypothesis in the toad-headed lizard Phrynocephalus przewalskii by comparing diet composition and prey sizes between males and females. The species was found to be sexual dimorphic, with males having relatively larger snout-vent length, head width, head length, and tail length, while females have relatively larger abdomen length. Based on analysis of 93 studied stomachs, a total of 1359 prey items were identified. The most common prey items were formicid, lygaeid and tenebrionid. The two sexes did not differ in the relative proportions of prey size categories they consumed and the dietary overlap based on prey species was high （O = 0.989）. In addition, the meal size, the volume or any maximal dimension of the largest prey item in the stomach was not explained by the sexes. According to our results, food niche divergence might not play an important role in the SSD evolution ofP. przewalskii.

Sexual Dimorphism in the Hindlimb Muscles of the Asiatic Toad(Bufo gargarizans)in Relation to Male Reproductive Success

In many anurans, the forelimb muscles of males are used to grasp females and are often heavier than those of females despite the larger female body size. Such sexual dimorphism in forelimb musculature is thought to result from sexual selection. In addition, the hindlimbs of frogs and toads play an important role in the reproductive process as amplectant males can expel rivals with robust hindlimbs through kicking. In this study, the sexual dimorphism in dry mass for six hindlimb muscles of the Asiatic toad （Bufo gargarizans） was investigated. The results showed that, when controlled for body size, the hindlimb muscle mass of males significantly exceeded that of females for every muscle. The hindlimb muscle mass of amplectant males was also significantly larger than that of non-amplectant males. These results suggested that if strong hindlimb muscles could improve mating success of males, sexual selection would promote the evolution of dimorphism in this character.

Dimorphism of Bivalved Arthropod Branchiocaris？ Yunnanensis from the Early Cambrian Chengjiang Biota, South China

The bivalved arthropod Branchiocaris？ yunnanensis Hou, 1987 is redescribed on the basis of new fossil material from the early Cambrian Chengjiang biota, South China. In total, 81 specimens have been examined. The carapace comprises two identical valves, each valve are sub-circular in outline, ranging from 24 mm to 58 mm in length, and from 15 mm to 46 mm in height. The dorsal margin is straight and bears two short cardinal spines. The valve surface is either smooth or ornamented with polygonal reticular structures, which may result from different preservation conditions. Two morphotypes have been recognized based on the presence or absence of a subdorsal swelling of the valve, which is convex dorsolaterally and extends beyond the dorsal margin when it appears. Statistic and ontogenetic analyses show both morphotypes grow isometrically and have the same growth trajectory. Therefore, the two morphotypes are interpreted as dimorphism within the same species. Our results are helpful for investigating the taxonomy and ontogeny of arthropod fossils and suggest that dimorphism might be fairly common in these early arthropods.

Sexual Dimorphism and Geographic Variation in the Asian Lance-headed Pitviper Protobothrops mucrosquamatus in the China's Mainland

Sexual dimorphism（SD） and geographic variation（GV） are widespread in snakes. Protobothrops mucrosquamatus（Cantor 1839） is one of the most common Asian venomous snakes with a wide geographical distribution. We examined SD and GV patterns for this species by using multivariate statistical analyses of external morphological characters scored from specimens from the China's Mainland. The result displayed that SD was significant in several external characters in P. mucrosquamatus, and the male P. mucrosquamatus formed two distinct clusters（Hainan Island and China's Mainland）, but the females did not. Based on our present work and the other data, we concluded that no significantly intraspecific differentiation is present within this species.

Intraspecific Variability and Problematic Dimorphism in the Early Cretaceous(Valanginian)Ammonite Saynoceras verrucosum(d'Orbigny,1841)

The population of Saynoceras verrucosum （d＇Orbigny） from the Polish basin （Wawal section, central Poland） shows no significant intraspecific variability. Dimorphism has not been found in this population. Statistical analyses of material from the shallow epicratonic Polish basin and the relatively deep Vocontian basin （southeastern France） indicated two populations. Forms from the Polish basin are somewhat more inflated and smaller than forms from the Vocontian basin.

Significant Male Biased Sexual Size Dimorphism in Leptobrachium leishanensis

Sexual size dimorphism（SSD） is a widespread phenomenon among animals, and whose evolution and maintenance has been a central topic in evolutionary biology since Darwin＇s time. SSD varies in direction among the major taxonomic groups of animals and even within the same groups. In anurans, female biased SSD is the rule in many lineages, whereas male biased SSD is a rare phenomenon. In this paper, we analyze whether SSD exists inLeptobrachium leishanensis by comparing morphological characteristics between the sexes. Our results show that all six morphological characteristics measured are significantly different between the sexes. Males are significantly larger than females, indicating that the male biased SSD of this species is apparent. The size of the nuptial spines, a special secondary sex trait of males, is significantly and positively correlated with body size. We suggest that the resource defense polygyny mating system and parental care behavior may be explanations for the evolution of male biased SSD and nuptial spine development in this species.

Thermoregulatory function and sexual dimorphism of the throat sack in Helmeted Guineafowl(Numida meleagris)across Africa

The responses of ground-dwelling birds to heat and cold stress encompass a variety of behavioural,physiological and even morphological mechanisms.However,the role of glabrous skin in this respect has been marginally addressed so far.The Helmeted Guineafowl(Numida meleagris)is a landfowl distributed across Sub-Saharan Africa with eight traditionally recognised extant subspecies.Among the most prominent morphological traits underlying intraspecific variability are size and pigmentation of the bare throat skin(or sack),which might be related to the different habitats and environmental conditions across its wide range.In order to explore the Helmeted Guineafowl range-wide sack variation and pigmentation in relation to thermoregulation and sexual signalling,we collected morphometric and environmental information for N.m.coronata integrating field data with the inspection of photographic material encompassing seven subspecies and environmental information from their habitats.Field data evidenced that sack size was significantly correlated with ambient temperature,thus pointing to a likely involvement of the throat sack in thermoregulation.When the pictorial data from all subspecies were pooled,sack size correlated negatively with biomass,rainfall and humidity,while a positive correlation was found with annual solar irradiation.Sack size correlated positively with monthly temperature variation among the bluethroated subspecies from southern Africa as opposed to the black-throated subspecies ranging north to Zambia and Mozambique.Still,in this latter group the sack was often larger during winter months,possibly to maximise solar radiation absorbance.Noteworthy,sack size was related to sex dimorphism in two subspecies.Sack morphology and colour in the Helmeted Guineafowl likely modulate body temperature by evaporative cooling or heating upon needs,but in some subspecies it is also seemingly related to sexual signalling.Additional studies are needed to fully understand the multifunctionality of this important morphological feature in this species.

In situ study of calcite-Ⅲ dimorphism using dynamic diamond anvil cell

The phase transitions among the high-pressure polymorphic forms of CaCO_(3)(cc-Ⅰ,cc-Ⅱ,cc-Ⅲ,and cc-Ⅲb)are investigated by dynamic diamond anvil cell(dDAC)and in situ Raman spectroscopy.Experiments are carried out at room temperature and high pressures up to 12.8 GPa with the pressurizing rate varying from 0.006 GPa/s to 0.056 GPa/s.In situ observation shows that with the increase of pressure,calcite transforms from cc-Ⅰto cc-Ⅱat~1.5 GPa and from cc-Ⅱto cc-Ⅲat~2.5 GPa,and transitions are independent of the pressurizing rate.Further,as the pressure continues to increase,the cc-Ⅲb begins to appear and coexists with cc-Ⅲwithin a pressure range that is inversely proportional to the pressurizing rate.At the pressurizing rates of 0.006,0.012,0.021,and 0.056 GPa/s,the coexistence pressure ranges of cc-Ⅲand cc-Ⅲb are 2.8 GPa-9.8 GPa,3.1 GPa-6.9 GPa,2.7 GPa-6.0 GPa,and 2.8 GPa-4.5 GPa,respectively.The dependence of the coexistence on the pressurizing rate may result from the influence of pressurizing rate on the activation process of transition by reducing the energy barrier.The higher the pressurizing rate,the lower the energy barrier is,and the easier it is to pull the system out of the coexistence state.The results of this in situ study provide new insights into the understanding of the phase transition of calcite.

Sexual dimorphism and sex-differential migration of Little Buntings(Emberiza pusilla)at an East Asian stopover site

Sex differences in morphology provide key information for understanding a species'morphological adaptations in relation to the evolution of sexual selection.In migratory birds,morphological traits have adapted to long-distance travel,and sexual dimorphism is typically related to sex-differential migration phenology.Little Buntings(Emberiza pusilla)have one of the longest migrations and are the least dichromatic species among the Emberiza buntings.In this study,we measured sexual size dimorphism and sexual dichromatism of Little Buntings in relation to the spring arrival dates at a stopover site in Korea.Wing length was the most important predictor for identifying sex;the wings of males were longer than those of females.Males also had a significantly stronger chestnut color of the head feathers than females,but this color difference was more prominent in the spring than in the fall.Males arrived earlier than females by four days.Arrival dates correlated with both size and color,but unlike other bunting species previously studied in the same area,there was no clear sex-differential trend in the relationship between arrival date and morphological characteristics.Seasonal differences in the degree of sexual dichromatism suggest that chestnut plumage coloration can be used as a social or sexual signal of males in the breeding season.The correlation of size and color to early arrival regardless of sex may indicate that a preference for assortative mating exists or that a sex-differential migration strategy is not clearly defined in the early stages of northward migration.Our findings on the sexual dimorphism of Little Buntings provide insight into the evolution of the sex-differential migration of buntings in the East Asian Flyway.

Sexual Dimorphism in Mass of the Hindlimb Muscles of the Piebald Odorous Frog(Odorrana schmackeri)

Male-biased sexual dimorphism in hind limb muscles is widespread in anuran species where scramble competition is common among males. Such sexual difference is thought to result from sexual selection. In this view, we tested the differences in muscle mass between the sexes and between amplectant and non-amplectant males by quantifying the mass of four hindlimb muscles （triceps femoris, sartorius, gracilis and plantaris longus） of females and males of Odorrana schmackeri. The results showed that females significantly exceeded males for muscle triceps femoris, gracilis, plantaris longus and total mass when controlled for body size. There are no significant differences between amplectant and non-amplectant males. It is probable that the maintenance of the amplectant position in O. schmackeri may depend on the strength of hindlimb muscles in females to support the pair.