山地麻蜥个体发育过程中头部两性异形和食性的变化

研究了山地麻蜥(Eremias brenchleyi)个体发育过程中头部两性异形和食性的变化．成体个体大小(SVL)无显著的两性差异,但雄体具有较大的头部(头长和头宽)．头部两性异形在孵出幼体就已存在,成体头部两性异形比幼体(包括孵出幼体)更为显著,雄性较大的头部与其头部随SVL的增长速率大于雌性有关．两性头部总体上随SVL呈异速增长,表现为个体发育过程中头长和头宽与SVL的线性回归方程斜率有显著的变化．孵出幼体有相对较大的头部,这种形态特征是胚胎优先保证生态学意义更为显著的头部生长的结果,有利于孵出幼体的早期生存和生长．相对头部大小在个体发育过程中有显著的变化．不同性别和大小的山地麻蜥摄入食物的种类及各种食物在摄入食物中所占的比例有一定程度的差别,食物生态位宽度和重叠度因此有一定的差别．然而,没有直接的证据表明头部两性异形能导致两性食物生态位的明显分离,并有利于减缓两性个体对食物资源的竞争。     

蓝尾石龙子的头部两性异形和食性

通过测量头、体大小和胃检研究浙江泰顺产蓝尾石龙子 (Eumeceselegans)个体发育过程中两性异形和食性的变化。蓝尾石龙子成体个体大小和头部大小的两性差异显著 ,雄性大于雌性。不同发育阶段雌性头长与SVL的线性回归斜率无显著差异 ,头宽与SVL线性回归斜率的差异显著 ,成体和SVL <5 0mm幼体头宽随SVL的增长速率显著小于SVL为 5 0 - 6 9mm的幼体。雄性头部相对于SVL呈加速式异速生长。两性比较发现 :雌雄幼体头长和头宽随SVL的增长速率无显著差异 ,SVL <5 0mm幼体特定SVL的头长和头宽无显著的两性差异 ,但SVL为 5 0 - 6 9mm的雄性幼体头长和头宽大于SVL相同的雌性幼体 ;雄性成体头长和头宽随SVL的增长速率显著大于雌性。SVL <5 0mm的雌性幼体头部相对小于SVL为 5 0 - 6 9mm的同性幼体 ,性成熟雌体头部相对小于SVL为 5 0 - 6 9mm的同性幼体。雌性幼体、雄性幼体、雌性成体和雄性成体食物生态位宽度分别为 12 3、 12 5、 4 8和 14 4。雌雄幼体食物生态位重叠度最高 ,雌雄成体食物生态位重叠度次之 ,成体与幼体食物生态位重叠度较小。成体摄入食饵的大小 (用胃内完整食物长度的平均值表示 )和变化范围大于幼体。两性成、幼体摄入的食饵大小差异显著。两性个体摄入的食饵大小均与其SVL呈正相关 ,表明较大     

吐鲁番沙虎头、体大小的两性异形及其食性的季节性变化

于2008年4月—2009年5月在新疆中国科学院吐鲁番沙漠植物园,捕获155号吐鲁番沙虎(Teratoscincus roborowskii)活体,对其两性异形和食性季节变化进行了研究,并收集单独暂养的吐鲁番沙虎粪便167份用于食性分析,同时测量各项形态学指标,切趾标记后放回原捕获地。结果表明:吐鲁番沙虎成体有两性异形,表现为雄性个体有较宽的头部,成体雌性具有较大的腋胯距;不同年龄组的两性个体头长和雄性个体的头宽随吻肛长都呈同速增长,只有雌性头宽的增长速率在个体发育过程中逐渐减小;吐鲁番沙虎摄入的动物性食物均为节肢动物,植物性食物为刺山柑果实。4—5月的生态位宽度为4.15,6—7月的生态位宽度为4.23,8—9月的生态位宽度为4.48。其中6—7月和8—9月的生态位重叠度最高。     

毛翼管鼻蝠性二型特征及其在湖北和浙江的分布新纪录

哺乳动物的性别二态性（Sexual dimorphism）是动物中的一种普遍现象,常表现为雄性个体大于雌性个体,而在蝙蝠中则表现出雌性个体体型大于雄性的偏雌性二型现象,其具体的驱动机制仍未明确。本文对采集于广东、广西、江西、湖南、海南、湖北和浙江的32只毛翼管鼻蝠（Harpiocephalus harpia）进行头骨与翼型在两性特征上的多元统计分析,尝试探讨其性二型驱动机制。结果表明：毛翼管鼻蝠雌雄在头骨中与牙齿及咀嚼力相关的区域存在明显分化,而翼型（含翼指标和翼面积）在整体和局部特征上均无显著性差异,该结果提示雌雄可能存在食性上的分化,更倾向于“资源竞争假说”而非“大母蝠优势假说”。本研究于2017年7~10月分别在湖北（3雄,2雌）和浙江（2雄,5雌）采集的12只毛翼管鼻蝠,为二省翼手目分布新纪录,该发现丰富和完善了我国翼手目分布信息。上述标本保存于广州大学华南生物多样性保护与利用重点实验室。     

Sexual dimorphism and mechanics of the human hip: A multivariate assessment

The present research was undertaken to determine the effects of sexual dimorphism in the human pelvis and femur on the mechanics of human locomotion. The analysis was based on six biomechanical variables determined from 25 male and 32 female skeletal remains from the Dickson Mound site. Discriminant function analysis indicates that the mechanical variables which primarily contribute to dimorphism are the moment arm of the gluteus medius and the torque produced by the abductors at the hip. These mechanical aspects of hip function produce greater pressure on the femoral head in females.     

Sexual dimorphism in the pelvic midplane and its relationship to Neandertal reproductive patterns

The fragmentary nature of the fossil record has limited the analysis of the Neandertal pelvis to the superior pubic ramus and the pelvic inlet. From an obstetric viewpoint, the pelvic midplane or “plane of least dimensions,” defined by the distance between the ischial spines, must be considered in the analysis of hominid reproduction. We examined the relationship between BSD and weight in a mixed sex hospital population undergoing diagnostic computed tomography (CT) scans (41 females and 40 males). Because femoral head diameter squared (FH²) has been used as a proxy for weight in skeletal populations, it was also analyzed with respect to BSD and weight. Bivariate regression analysis of BSD with other body dimensions indicates the presence of significant sex differences. In females, but not in males, weight is a statistically significant predictor of BSD. FH² is an even better predictor of BSD in females while nonsignificant in males. Although weight and FH² are significantly correlated with BSD in females, FH² does not predict weight in females as well as it does in males. The positive correlation between skeletal frame size and BSD in females is indicative of an evolutionary pattern that must take into account the pressures of reproduction. Our results indicate that critical dimensions of the pelvis must increase as the maternal skeleton becomes larger. These results provide a context for the interpretation of the reproductive patterns of a relatively robust hominid population like the Neandertals. © 1996 Wiley-Liss, Inc.     

Sexual dimorphism in the emergence of deciduous teeth: its relationship with growth components in height

Sexual dimorphism in the emergence of the deciduous dentition of French-Canadian children may be explained by differences in recumbent length. Relative to the chronological age scale, boys are longer and their teeth emerge earlier than girls. Recumbent lengths attained at the exact age of emergence, as estimated by fifth-order polynomials fitted to each subject's serial data, are comparable between the sexes. Multi- and univariate analyses of variance show no significant sex differences in the lengths attained at the age of emergence of the deciduous teeth. These findings suggest that clinical standards for emergence of deciduous teeth scaled relative to length rather than chronological age are more accurate and efficient.     

Sexual dimorphism in the human bony pelvis, with a consideration of the Neandertal pelvis from Kebara Cave, Israel.

Sexual dimorphism of the human pelvis is inferentially related to obstetrics. However, researchers disagree in the identification and obstetric significance of pelvic dimorphisms. This study addresses three issues. First, common patterns in dimorphism are identified by analysis of pelvimetrics from six independent samples (Whites and Blacks of known sex and four Amerindian samples of unknown sex). Second, an hypothesis is tested that the index of pelvic dimorphism (female mean x 100/male mean) is inversely related to pelvic variability. Third, the pelvic dimensions of the Neandertal male from Kebara cave, Israel are compared with those of the males in this study. The results show that the pelvic inlet is the plane of least dimorphism in humans. The reason that reports often differ in the identification of dimorphisms for this pelvic plane is that both the length of the pubis and the shape of the inlet are related to nutrition. The dimensions of the pelvis that are most dimorphic (that is, female larger than male) are the measures of posterior space, angulation of sacrum, biischial breadth, and subpubic angle. Interestingly, these dimensions are also the most variable. The hypothesis that variability and dimorphism are inversely related fails to be supported. The factors that influence pelvic variability are discussed. The Kebara 2 pelvis has a spacious inlet and a confined outlet relative to modern males, though the circumferences of both planes in the Neandertal are within the range of variation of modern males. The inference is that outlet circumference in Neandertal females is also small in size, but within the range of variation of modern females. Arguments that Neandertal newborns were larger in size than those of modern humans necessarily imply that birth was more difficult in Neandertals.     

Sexual dimorphism on the neurogenic potential of rhesus monkeys mesenchymal stem cells

Bone marrow mesenchymal stem cells (BMSCs) have been shown to differentiate into cells of a neural lineage. However, no studies have examined whether gender influences the differentiation potential of BMSCs. Here, we explore the possible differences in BMSC’s neurogenic potential in vitro between female rhesus monkey BMSCs (F-rhBMSCs) and male rhBMSCs (M-rhBMSCs). We first isolated and cultured rhBMSCs from female and male donors (n = 6, 2 years old), identified their sex origin by karyotype assay, and assessed their expression of nestin and CD34 at passage 1 and 10. Then, nestin-positive F- and M-rhBMSCs at P10 were differentiated into neural-like cells. After induction, the neurogenic potential of these cells was assessed by morphological observation and protein expression analysis of neural markers, including class III β-tubulin, neurofilament light polypeptide, tau, and gamma-aminobutyric acid (GABA) neurotransmitter. Furthermore, GABA content was assayed using high-pressure liquid chromatography. The results showed that F-rhBMSCs produced significantly more nestin-positive cells compared with M-rhBMSCs at P10 and that nestin-positive F-rhBMSCs acquired higher neurogenic potential accompanied by increased synthesis and excretion of GABA compared with nestin-positive M-rhBMSCs under conditions of differentiation. These results indicated that gender may play an important role in the neurogenic potential of BMSCs, and a further understanding of the cellular biology underlying these differences may contribute to the development of new therapeutic strategies for neurological repair and regeneration.     

Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan

The maturation and growth pattern of the fluvial eight-barbel loach Lefua sp. (Japanese name: nagare-hotoke-dojo), an endangered species, was investigated using an individual identification-recapture method from 1995 to 1998 in an upper reach of a headwater tributary of the Kako River, Hyogo Prefecture, Japan. Based on observations of the gonads through the abdominal skin, the loach was estimated to breed mostly from May to July. All the males matured by age 1⁺, and all the females matured by age 2⁺. Gamete release in all individuals of both males and females was predicted from recaptured loaches during each breeding season. The standard length of mature females was significantly larger than that of males, showing sexual size dimorphism (SSD). The maximum sizes recorded were 75.4 mm SL for females and 61.2 mm SL for males. Both males and females of immature specimens grew mainly from May to November, including the breeding season, with no significant differences in growth rates between them. After sexual maturity, both males and females grew mainly from July to October (or November), after the breeding season, and the females exhibited higher growth rates than males. Therefore, SSD of the species seems to be attributable to the different growth rates after maturity. The longevity of the loach was estimated to exceed ten years based on individual growth patterns of various sizes during the survey period. It is likely that the loach has an iteroparous life history, breeding every year, and moderate growth rates after maturity.     

Sexual dimorphism and the influence of artificial elevated temperatures on body size in the imago of Nemoura trispinosa (Plecoptera: Nemouridae)

Our study site was composed of a spring that was divided lengthwise from its source into two equally wide channels, with water temperature in the experimental channel being increased by 2.0–3.5°C relative to that of the control channel. We examined sexual dimorphism in overall body size and eight morphological traits in the stonefly Nemoura trispinosa Claassen, and whether body size varies according to site of emergence (upstream versus downstream) and/or the thermal regime in which they undergo nymphal development. Univariate tests showed that females were significantly larger than males in all eight traits, and multivariate analyses (Principal Components Analysis) demonstrated that females were larger in overall body size. Both univariate and multivariate tests showed that adults emerging from the control and downstream portions of the stream were larger than those from heated and upstream reaches, respectively. We discuss possible hypotheses contributing to the female-biased sexual dimorphism observed in this species.     

Sexual dimorphism, female reproduction and egg incubation in the oriental leaf-toed gecko (Hemidactylus bowringii) from southern China

We studied sexual dimorphism, female reproduction and egg incubation of the oriental leaf-toed gecko (Hemidactylus bowringii) from a population in southern China. The largest male and female in our sample were 60 and 57 mm snout-vent length (SVL), respectively. Males are the larger sex; sexual dimorphism in head size and tail length (TL) is evident in juveniles and adults, with males having larger heads as well as longer tails than females. Oviposition occurred between late May and late July. Females switched from laying two eggs early in the breeding season to 1-2 eggs later in the season. Clutch mass and egg mass were both independent of female SVL, whereas relative clutch mass was negatively correlated with female SVL. The previous conclusion that female H. bowringii lay a single clutch of eggs per breeding season is unlikely to be true. Thermal environments experienced by H. bowringii eggs affect incubation length as well as morphological and locomotor phenotypes of hatchlings. Hatchlings from eggs incubated at 30 degrees C were larger (SVL, tail length and body mass) and performed better in the racetrack than their counterparts from eggs incubated at 24 degrees C. Temperatures suitable for embryonic development are relatively high in H. bowringii, primarily as a consequence of the adaptive response to warm environments in southern China.     

Sexual dimorphism of the human mandible and its association with dental development

The present study investigates whether the human mandible is sexually dimorphic during early postnatal development and whether early dimorphic features persist during subsequent ontogeny. We also examine whether mandibular dimorphism is linked to dimorphism of dental development. Dense CT-derived mandibular meshes of 84 females and 75 males, ranging from birth to adulthood, were analyzed using geometric morphometric methods. On the basis of the specimen's chronological ages and mineralization stages of the deciduous and permanent teeth, we compute dental age as proxy for dental development by the additive conjoint measurement method. By birth, males have, on average, more advanced age-specific shapes than females. However, sex differences decrease quickly as females catch up via a different association between shape and size. This leads to an almost complete reduction of sexual dimorphism between the ages of 4 and 14. From puberty to adulthood, males are characterized by allometric shape changes while the shape of the female mandible continues to change even after size has ceased to increase. Dimorphism of dental maturation becomes visible only at puberty. Sexual dimorphism, concentrated at the ramus and the mental region during the earliest ontogenetic stages and again at adulthood, is not associated with the development of the teeth. At puberty there is a simultaneous peak in size increase, shape development, and dental maturation likely controlled by the surge of sex hormones with a dimorphic onset age. We argue that the infant and adult dimorphism of the mental region may be associated with the development of supralaryngeal structures.     

饶阳地区三种农田啮齿类头骨形态比较及性二型

关于动物头骨形态方面的研究报道曾受到了较多的关注（Cesani et al., 2003）.头骨形态是动物形态特征的一个重要方面,受遗传和环境因素的共同影响,存在着种间、性别和地理差异（张焱等,1999）.头骨的形态特征不仅是动物生理上的一个基本解剖指标,同时也是动物分类（李晓晨和王廷正,1992）和年龄鉴定（张洁,1989）的重要依据,是动物生态研究的重要指标.对头骨形态的研究,不仅对动物的种间、种内关系（Yom et al.,1999）和生态特征（Barlow et al.,1997）等方面的研究具有重要的参考价值,在动物的地理演化、发育生物学以及进化生态学的研究中也具有十分重要的意义.     

Sexual size dimorphism, growth and maturity of the Japanese fluvial sculpin,Cottus pollux (large egg type), in the Inabe River, Mie prefecture, central Japan

The population structure of the Japanese fluvial sculpin,Cottus pollux (large egg type), in the upper reaches of the Inabe River, Mie Prefecture, central Japan, was investigated by a mark-and-recapture method from July 1989 to January 1991. Breeding of the species occurred from mid February to early May, peaking from mid February to late March. The mean size of mature males observed in March 1990 was significantly larger than that of females, showing apparent sexual size dimorphism. Data analysis of the growth of 1658 marked individuals revealed that the species matured at 2 years of age in both sexes. Whereas 1 year old males reached ca. 50–70 mm SL, females were less than 50 mm SL at the same age, size dimorphism already being apparent. Immature males exhibited higher growth rates than females during their first and second years, some of the former outstripping mature males of the preceding year class in total length. After attaining sexual maturity, both males and females grew mainly from July to December, with no significant differences in mean growth rate between them. Sexual size dimorphism of the species seems to be attributable to different growth rates between the sexes during their immature stage.     

Sexual size dimorphism and selection in the wild in the waterstrider Aquarius remigis: Body size,components of body size and male mating success

Sexual size dimorphism is assumed to be adaptive and is expected to evolve in response to a difference in the net selection pressures on the sexes. Although a demonstration of sexual selection is neither necessary nor sufficient to explain the evolution of sexual size dimorphism, sexual selection is generally assumed to be a major evolutionary force. If contemporary sexual selection is important in the evolution and maintenance of sexual size dimorphism then we expect to see concordance between patterns of sexual selection and patterns of sexual dimorphism. We examined sexual selection in the wild, acting on male body size, and components of body size, in the waterstrider Aquarius remigis, as part of a long term study examining net selection pressures on the two sexes in this species. Selection was estimated on both a daily and annual basis. Since our measure of fitness (mating success) was behavioral, we estimated reliabilities to determine if males perform consistently. Reliabilities were measured as ? statistics and range from fair to perfect agreement with substantial agreement overall. We found significant univariate sexual selection favoring larger total length in the first year of our study but not in the second. Multivariate analysis of components of body size revealed that sexual selection for larger males was not acting directly on total length but on genital length. Sexual selection for larger male body size was opposed by direct selection favoring smaller midfemoral lengths. While males of this species are smaller than females, they have longer genital segments and wider forefemora. Patterns of contemporary sexual selection and sexual size dimorphism agree only for genital length. For total length, and all other components of body size examined, contemporary sexual selection was either nonsignificant or opposed the pattern of size dimporhism. Thus, while the net pressures of contemporary selection for the species may still act to maintain sexual size dimorphism, sexual selection alone does not.     

The rabbit submandibular gland: sexual dimorphism, effects of gonadectomy, and variations across the female reproductive cycle

Sex differences and the effect of various endocrine conditions on the histology of the rabbit (Oryctolagus cuniculus L.) submandibular (chin) gland were investigated. The female gland contained significantly more acini/field than the male gland. The diameter of acini was significantly smaller than those of the male gland. Gonadectomy reduced the number of acini/field and increased their diameter in females but provoked the opposite effect in males. Gonadectomy drastically reduced the percent of acini with crystal bodies in both sexes, and the percent of acini with apocrine secretion only in females. Estrous does showed a significantly higher number of acini/field than pregnant (days 20 and 29) and lactating (day 6) does. Acini containing crystal bodies declined from 22% in estrous females to 8% and 3% in pre-parturient (gestation day 31) and lactating (day 6) does, respectively. By contrast, acini showing apocrine secretion increased from 12% in estrous females to 43% in pre-parturient does and declined to 23% on lactation day 6. In all glands glycoproteins were noted in crystal bodies but not in apocrine secretion. Results show a sexual dimorphism in the rabbit chin gland histology and support the participation of gonadal steroids in its physiological regulation.Abbreviations GNX gonadectomized - PAS periodic acid Schiff - PASD periodic acid Schiff-diastase     

Sexual dimorphism,phenotypic integration,and the evolution of head structure in casque‐headed lizards

Sexes can differ in features associated with differential reproduction, which can be used during courtship or aggressive encounters. Some traits tend to evolve independently between sexes and emerge as sexually dimorphic within the organismal phenotype. We characterize such a relationship by estimating the phenotypic integration of the head morphology and modularity of the crest in the casque‐headed lizards (Corytophanidae). In this clade, some species show extreme sexual dimorphism (e.g., head crests in the genus Basiliscus) while in others, both sexes are monomorphic. To characterize these patterns, we define phenotypic integration at the interspecific level as a pattern or network of traits evidenced by phylogenetically adjusted correlations that persist among species. At this level, modularity is an increased connectedness (e.g., higher correlation) among sections of these networks that persist in a lineage during the evolution of complex phenotypes. To test both concepts, we used phylogenetic geomorphometrics to characterize the head structure of corytophanid lizards, based on a time‐calibrated phylogeny that includes candidate fossil ancestors. We found evidence of an older diversification of corytophanids than previously reported (~67 vs. ~23.5 MYA) and show that this clade includes two morphological head architectures: (1) Sexually dimorphic crests present in males that are evolving independently from the rest of the head structure, and (2) full integration of the head morphology in monomorphic species. We propose that both architectures are optimal evolutionary trajectories of the parietal crest bones in the head of these lizards. In sexually dimorphic species, these bones are elongated and thinner, and gave rise to the extended crest used in male courtship displays. In monomorphic species, the parietal crest grew thicker in both sexes to allow for a better insertion of muscles associated with a stronger bite.