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1.
Many characteristics of the human skeleton can only be assessed morphologically, which may be problematic due to factors such as interobserver error and difficulties with standardization. Flexure of the mandibular ramus is one of these traits, and various researchers found widely differing results using this morphological feature. The aim of this study was to determine whether differences between male and female mandibular rami could be observed using the computerized method of geometric morphometrics, a valuable tool that helps quantify shape differences. Twenty-eight mandibular rami of black females and 43 of black males were photographed in a standard plane and assessed. It was found that the females were more scattered on the graph (more variable in shape), while the males clustered more around the center point where the two axes met (shape more constant). There was, however, considerable overlap between the sexes. Although different tendencies exist between the rami of males (being more flexed) and females (tending to be straight), the extent of these differences is not adequate to predict the sex of a single individual. 相似文献
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Using Schutkowski's method for juvenile sex determination (Schutkowski H. 1993. Am J Phys Anthropol 90:199-205), we evaluated the morphology of the greater sciatic notch of 56 ilia (23 females and 33 males) from a documented skeletal collection housed at the Bocage Museum in Lisbon (Portugal). After applying Schutkowski's original methodology and comparing the results with previous studies, we used age-adjusted metrical variables to describe greater sciatic notch depth, breadth, and angle. Although results of both morphological and metrical analyses did not reveal a statistically significant level of sexual analyses dimorphism, we found a strong correlation between pelvic morphology and age at death. On the basis of the obtained results, we argue that Schutkowski's morphological method does not predict sex accurately in all populations and that recorded correlation of iliac features with age needs to be further explored in the context of the ontogeny of sexual dimorphism. 相似文献
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Coquerelle M Bookstein FL Braga J Halazonetis DJ Weber GW Mitteroecker P 《American journal of physical anthropology》2011,145(2):192-202
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. 相似文献
4.
Elena Vortsepneva Alexander Tzetlin Günter Purschke Nikolai Mugue Eva Haß-Cordes Anna Zhadan 《Invertebrate Biology》2008,127(4):403-416
Abstract. The morphology of the obligately ectoparasitic polychaete Asetocalamyzas laonicola was studied by light and electron microscopy, and its taxonomic position was determined using molecular methods. The parasite has an extensive coelomic cavity, complete septae, and well-developed segmental nephridia, circulatory, and digestive systems. The nervous system is rudimentary and without ganglia. The parasite's anterior region penetrates the tissues of the host, and opens into the host's body cavity. The epidermal tissues of the parasite and the host are highly integrated in the area of contact, and the parasite's cuticle is continuous with that of the host. Blood vessels of the parasite and the host may interlace in the fusion zone. The dorsal side of the parasite faces the dorsal side of the host. All parasites were males, but all hosts were females. In order to elucidate the uncertain systematic position of the parasite, molecular systematic studies were conducted. Parasite and host 18S rDNA sequences were virtually identical and revealed that both belong to the spionid cluster. These sequences differed from those of Scolelepis squamata and Scolelepis bonnieri by 2.7% and 0.9%, respectively. In addition, of seven partial sequences of the mitochondrial COI gene obtained from three parasites and four hosts, six were identical, and in one host–parasite pair, COI sequences differed by one substitution. Partial ITS2 sequences from one host–parasite pair were analyzed and also found to be similar but not identical, with two indels in a 645-bp alignment. We conclude that the parasite is in fact a dwarf male of its conspecific spionid female host. Consequently, A. laonicola is transferred to Scolelepis (Spionidae), forming the new combination Scolelepis laonicola. 相似文献
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Sexual dimorphism in growth of conventional morphometric characters was investigated in juveniles and young adults (size range: 31 to 91 mm) of Oreochromis mossambicus . A closely associated set of traits was identified that shows sexually dimorphic growth, which was positively allometric in the males. These traits correspond to two different morphological complexes: jaw structure and anal/dorsal fins. The best sex discriminators among this set of traits were premaxilla width, anal fin height and snout length. These findings may be explained in terms of intra– and inter–sexual selection acting together and favouring males with strong and large mouths and high dorsal and anal fins, traits that are important in agonistic displays (jaw and fins), fighting and nest digging (jaw). 相似文献
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【目的】为了从生物学和化学生态学角度探讨弯头细蛾Epicephala ancylopa和寄主三室算盘子Glochidion sp.间专性传粉的互利共生关系稳定性。【方法】本研究在野外观察和室内实验的基础上,对专性传粉育幼互利共生体系中三室算盘子、弯头细蛾生物学特性进行详细研究,探究互利共生双方利益得失;用动态顶空吸附法分别收集三室算盘子雄花和雌花气味物质,运用气相色谱-质谱联用技术(GC-MS)分析并鉴定其有效成分,用峰面积归一化与内标法定性定量;最后通过主成分分析法比较雄花和雌花之间气味化学成分的差异性。【结果】弯头细蛾在云南省普洱太阳河国家森林公园每年有1个世代,成虫和幼虫的活动时间分别在3-4月和8-10月。三室算盘子结实率为44.20%,被蛀食率为69.94%,平均每头幼虫消耗2.55枚种子来满足自身生长发育,寄主植物留有83.06%完好的种子,以维持互利共生关系的稳定。三室算盘子雌雄花气味中共鉴定出24种挥发物,主要以单萜类和倍半萜类物质为主,其中(Z)-罗勒烯和β-榄香烯两种萜类物质含量最高(分别为47.11%和22.72%),推测其是吸引弯头细蛾传粉的主要气味成分;雄花和雌花之间气味化学成分存在明显的差异,具有两性异型性。【结论】弯头细蛾通过以卵越夏和以蛹越冬对策,实现成虫发生期与三室算盘子花期的精准匹配。弯头细蛾成虫白天静伏,傍晚开始活动,三室算盘子花的气味物质也只在晚上才明显释放,且雌雄花气味化学成分的两性异型性有利于弯头细蛾辨别雌雄花,以完成采集花粉与传粉行为。该研究结果为头细蛾属昆虫与算盘子属植物专性传粉互利共生关系稳定性的维持机制提供了新的依据,也为深入开展通过触角电生理检测和生物行为实验来筛选吸引传粉头细蛾的活性物质提供了理论依据。 相似文献
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JONATHAN BRECKO KATLEEN HUYGHE BIEKE VANHOOYDONCK ANTHONY HERREL IRENA GRBAC RAOUL VAN DAMME 《Biological journal of the Linnean Society. Linnean Society of London》2008,94(2):251-264
Within populations, individual animals may vary considerably in morphology and ecology. The degree to which variation in morphology is related to ecological variation within a population remains largely unexplored. We investigated whether variation in body size and shape among sexes and age classes of the lizard Podarcis melisellensis translates in differential whole-animal performance (sprint speed, bite force), escape and prey attack behaviour in the field, microhabitat use and diet. Male and female adult lizards differed significantly in body size and head and limb proportions. These morphological differences were reflected in differences in bite strength, but not in sprint speed. Accordingly, field measurements of escape behaviour and prey attack speed did not differ between the sexes, but males ate larger, harder and faster prey than females. In addition to differences in body size, juveniles diverged from adults in relative limb and head dimensions. These shape differences may explain the relatively high sprint and bite capacities of juvenile lizards. Ontogenetic variation in morphology and performance is strongly reflected in the behaviour and ecology in the field, with juveniles differing from adults in aspects of their microhabitat use, escape behaviour and diet. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 251–264. 相似文献
9.
C. Wemmer V. Krishnamurthy S. Shrestha L.‐A. Hayek Myo Thant K.A. Nanjappa 《Zoo biology》2006,25(3):187-200
A method of assessing body condition of Asian elephants (Elephas maximus) is presented. The method uses visual assessment to assign numerical scores to six different regions of the body, which are totaled to give a numerical index ranging from 0–11. The relationship between the index and morphometric variables is compared for a sample of 119 juvenile and young adult elephants from southern India, Nepal, and Myanmar. Mean ages of males and females were similar. Mean index of body condition (with standard error [SE]) was 7.3±0.2 points. No significant correlation was found between index of body condition and age over both sexes (r=0.01, n=50). Results were equivalent when sexes were treated separately (females: r=0.03, n=24; males: r=0.01, n=26). Sexes did not differ in height of the shoulder or body condition in our sample, but there was significant sexual dimorphism in breadth of the zygomatic arch and three measures of subcutaneous fat: girth of neck, thickness of cervical fold, and thickness of anal flap. These three measures were also significantly correlated with each other. Our assessment method should prove a practical tool for ecologic studies, but the relationship of the index to percentage of body fat should be determined using heavy water dilution methodology. Zoo Biol 25:187–200, 2006. © 2006 Wiley‐Liss, Inc. 相似文献
10.
Bones of the face and cranial vault meet at sutural boundaries. These sutures are of great importance for craniofacial growth. Although the effects that the sutures have on modulating craniofacial strains have been investigated, how sutural fusion influences primate craniofacial biomechanics and adaptation are less considered. Confounding this problem is the lack of any systematic data on patterns of craniofacial sutural fusion from animals of known age and sex. This study examined the status of 28 sutures in Macaca mulatta skulls from a collection of animals of known age and sex from Cayo Santiago, Puerto Rico. Survival analysis showed that most animals died before all sutures fused. There was high variation in the age at which individual sutures or sutural sections were fused in M. mulatta, and significant differences in the amount of sutural fusion among regions and between males and females. Intensive fusion of sutures took place between ages 5 and 15. Sutures in the facial area tended to be less fused than in the cranial vault. Between adolescence and adulthood, males tended to have more sutural fusion than females, especially in the facial area. These differences might be biomechanical adaptations during ontogeny to craniofacial sexual dimorphism. These findings enrich our understanding of variation in sutural morphology in rhesus monkeys. Comparative information across primate species is essential for understanding the biomechanics of craniofacial form throughout primate evolution. 相似文献
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Within Richardiidae, Richardia infestans, from Colombia, is the only known species to have genal processes, which are structures formed by the extension of the cuticle on the lateral margin of the gena. In the present work, six new species, with different patterns of antler‐like genal processes, are described. An identification key and illustrations are provided. Richardia bella sp. nov. , R. modesta sp. nov. and R. vitta sp. nov. are recorded from Costa Rica; R. advena sp. nov. is recorded from Costa Rica and Panama; R. simplex sp. nov. is recorded from Panama; and R. ornatella sp. nov. is recorded from Ecuador. 相似文献
13.
The European swallowtail butterfly (Papilio machaon) is so named, because of the long and narrow prominences extending from the trailing edge of their hindwings and, although not a true tail, they are referred to as such. Despite being a defining feature, an unequivocal function for the tails is yet to be determined, with predator avoidance (diverting an attack from the rest of the body), and enhancement of aerodynamic performance suggested. The swallowtail, however, is sexually size dimorphic with females larger than males, but whether the tail is also sexually dimorphic is unknown. Here, museum specimens were used to determine whether sexual selection has played a role in the evolution of the swallowtail butterfly tails in a similar way to that seen in the tail streamers of the barn swallow (Hirundo rustica), where the males have longer streamers than those of the females. Previously identified sexual dimorphism in swallowtail butterfly size was replicated, but no evidence for dimorphism in tail length was found. If evolved to mimic antennae and a head to divert a predatory attack, and if an absolute tail size was the most effective for this, then the tail would probably be invariant with butterfly hindwing size. The slope of the relationship between tail length and size, however, although close to zero, was nonetheless statistically significantly above (tail length ∝ hindwing area 0.107 ± 0.011). The slope also did not equate to that expected for geometric similarity (tail length ∝ hindwing area1/2) suggesting that tail morphology is not solely driven by aerodynamics. It seems likely then, that tail morphology is primarily determined by, and perhaps a compromise of several, factors associated with predator avoidance (e.g. false head mimicry and a startling function). Of course, experimental data are required to confirm this. 相似文献
14.
Plavcan JM 《American journal of physical anthropology》2003,120(1):38-60
Craniofacial remains (the most abundant identifiable remains in the fossil record) potentially offer important information about body size dimorphism in extinct species. This study evaluates the scaling relationships between body mass dimorphism and different measures of craniofacial dimorphism, evaluating taxonomic differences in the magnitude and scaling of craniofacial dimorphism across higher taxonomic groups. Data on 40 dimensions from 129 primate species and subspecies demonstrate that few dimensions change proportionally with body mass dimorphism. Primates show general patterns of greater facial vs. neurocranial and orbital dimorphism, and greater dimorphism in lengths as opposed to breadths. Within any species, though, different craniofacial dimensions can yield very different reconstructions of size dimorphism. There are significant taxonomic differences in the relationships between size and craniofacial dimorphism among primate groups that can have a significant impact on reconstructions of body mass dimorphism. Hominoids tend to show lower degrees of facial dimorphism proportional to size dimorphism than other primates. This in turn implies that strong craniofacial dimorphism in Australopithecus africanus could imply very strong body size dimorphism, conflicting with the relatively modest size dimorphism inferred from postcrania. Different methods of estimating the magnitude of size dimorphism from craniofacial measurements yield similar results, and yield comparatively low percent prediction errors for a number of dimensions. However, confidence intervals for most estimates are so large as to render most estimates highly tentative. 相似文献
15.
Richard A. Lazenby 《American journal of physical anthropology》1998,106(2):157-167
Study of bone mass at the second metacarpal midshaft has contributed to our understanding of skeletal growth and aging within and between populations and has relied extensively on noninvasive techniques and in particular radiogrammetric data. This study reports age, sex, and side variation in size and shape data acquired from direct measurement of cross-sections obtained from a large (n = 356), homogeneous skeletal sample. Correlation analysis and three-way ANOVA of size-adjusted data confirm general impressions of patterned variation in this element: males have absolutely but not necessarily relatively larger bones than females; the right side is larger than the left, though a larger than expected proportion (approximately 25%) of left metacarpals exhibits greater values than the right; and bone mass but not strength (in males) declines with age. Contrary to the widely accepted assumption of circularity for this location, direct measurement of cross-sectional geometry confirms previous biplanar radiogrammetric conclusions regarding the noncircularity of the second metacarpal midshaft and identifies a significant difference between males and females, with the latter having a more cylindrical diaphysis. Deviation of the axes of maximum and minimum bending strength associated with noncircularity suggests a distribution of bone mass to resist bending moments perpendicular to the distal palmar arch, though this conclusion awaits more robust study of the functional anatomy of the metacarpal diaphysis. Am J Phys Anthropol 106:157–167, 1998. © 1998 Wiley-Liss, Inc. 相似文献
16.
THAN THAN LWIN WATARU DOI MASASHI YOKOTA CARLOS AUGUSTO STRÜSSMANN SEIICHI WATANABE 《Invertebrate reproduction & development.》2013,57(4):191-201
Summary The morphometrical and meristic features of the carapace, cephalic appendages (antenna, antennule), mouthparts (maxillule, maxilla, first-third maxillipeds), sternum, pereiopods, abdomen, and pleopods of juveniles and the onset of morphological sexual dimorphism were described for the xanthid crab Leptodius exaratus (H. Milne Edwards, 1834), based on laboratory-reared and wild adult specimens collected from Tateyama Bay, Japan. First instar juveniles shared some of the features of adults (e.g. gross appearance of the carapace and cheliped propodus proportions), but differed from adults on almost all other morphological parameter examined. Morphological development was still not complete at the ninth instar; extrapolation from the rate of morphological changes between instars 1–9 suggests that L. exaratus requires about 13 ecdyses to transform into adults, including development of reproductive structures. Differences in the number and morphology of pleopods and abdomen width allowed early distinction of the sexes. Thus, males formed gonopods in the first abdominal somite and lost the paired vestigial pleopods in somites 3–5 from the fourth instar; females retained the pleopods in somites 2–5, but these became biramous and had increased setation. The abdomen grew wider in females than in males from the fifth instar. Several morphological features of juveniles have phylogenetic and taxonomic implications: carapace motifs clearly place L. exaratus in the superfamily Xanthoidea, whereas the patterns of setation in the scaphognathite and first maxilliped epipod allow separation of this (xanthid) species from crabs of other Xanthoidean families. 相似文献
17.
榆树隐毡蚧 Cryptococcus ulmi Tang et Hao是近年来在北京和山西中部发现的一种榆树新害虫。本文首次详细记述和图示了该虫幼期各虫态和雄成虫的形态特征 ;简要报道了其生物学特性 :一年发生 1代 ,以受精雌成虫在树干裂缝内越冬 ,卵胎生 ,每雌产仔 2 3～ 2 5头 ,平均值 35.2头。 相似文献
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Kaliope Katsikaros Richard Shine 《Biological journal of the Linnean Society. Linnean Society of London》1997,60(1):39-51
At least two adaptive processes can lead to the evolution of sexual dimorphism: sexual selection (e.g. male-male combat) or natural selection (e.g. dietary divergence). We investigated the adaptive significance of a distinctive pattern of sexual dimorphism in a south-eastern Australian frog, Adelotus brevis. Male Adelotus grow larger than female conspecifics, have larger heads relative to body size, and have large paired projections (‘tusks’) in the lower jaw. All of these traits are rare among anurans. We quantified the degree of dimorphism in Adelotus, and gathered data on diets and mating systems of this species to evaluate the possible roles of sexual selection and dietary divergence in favoring die evolution of these sexually dimorphic traits. Analysis of prey items in alimentary tracts revealed significant sex differences in prey types. For example, females ate proportionally more arthropods and fewer molluscs than did males. However, this difference is likely to be a secondary consequence of habitat differences between the sexes (due in turn to their different reproductive roles) rather than a selective force for the evolution of sexual dimorphism. Calling males spend their time in moist habitats where pondsnails are abundant, whereas females are more often encountered in the drier arthropod-rich woodlands. A three-year behavioural ecology study on a field population revealed that reproductive males engage in agonistic interactions, with the sexually dimorphic tusks used to attack rivals. Larger body size contributed to male reproductive success. Small males were excluded from calling sites and, among the calling males, larger animals had higher reproductive success (numbers of matings) than did smaller individuals. Hence, the atypical pattern of sexual dimorphism in Adelotus brevis seems to have resulted from sexual selection for larger body size and tusk size in males, in the context of male-male agonistic behaviour, rather than natural selection for ecological divergence between the sexes. 相似文献
19.
Schulte-Hostedde AI Kuula S Martin C Schank CC Lesbarrères D 《Journal of evolutionary biology》2011,24(5):1154-1159
Allometry of secondary sexual traits has been the subject of recent debate, and the generality of positive allometry and its association with sexual selection have been recently questioned. Whereas some studies suggest an almost universal positive allometry for traits under sexual selection and isometry or a negative allometry for traits not under such pressure, other studies argue that this pattern results from the study of exaggerated (ornamental) traits. To answer the call for an examination of the allometry of less-exaggerated sexually selected traits, we have examined morphological data from 14 sexually dimorphic traits and six monomorphic traits from three anuran species. Although we found evidence of positive allometry in male secondary sexual traits of several species and populations, not all nonsexual traits were isometric or exhibited negative allometry. Furthermore, our results indicate that larger traits in the populations that we studied were not associated with greater allometric slopes. Therefore, our study is in line with the contention suggesting no specific kind of allometric pattern for sexual and nonsexual characters, and we can only advocate for further investigation of trait allometry and sexual selection to understand the complexity underlying the evolution of allometry in sexual traits. 相似文献
20.
Saddle-back tamarins (Saguinus fuscicollis) have been differentiated into subspecies based on coat color and facial morphology. Morphology of first-generation genetic hybrids can provide an understanding of population differences and evolution that may otherwise be difficult to obtain. This study compares postcranial morphology in two hybrids of saddle-back tamarins (S. f. illigeri x S. f. lagonotus and S. f. illigeri x S. f. leucogenys) to the purebred subspecies. We examine whether postcranial morphology differs between the purebred subspecies and their hybrids, and whether hybrids exhibit heterosis indicative of genetic differences between the parental subspecies. Fifty postcranial dimensions, or traits, were measured on 287 S. fuscicollis skeletons. Measurements were corrected for sex differences and environmental differences (wild-derived or laboratory-born). Females were larger than males for most postcranial dimensions, especially in the pelvis. Significant environmental differences were found throughout the postcranial skeleton, with wild-derived animals generally larger than animals born in the laboratory. Significant heterosis was found for six postcranial traits in the S. f. illigeri x S. f. leucogenys cross, and heterosis was found for 15 postcranial traits in the S. f. illigeri x S. f. lagonotus cross. These results suggest that subspecies differences in skeletal morphology are generally due to genetic rather than environmental differences. The subspecies appear to represent geographic isolates that differ in gene frequencies and directional dominance for skeletal traits. 相似文献