人类股骨断面面积与形状的不对称性——基于三维激光扫描的形态测量分析

人类股骨横断面面积、形状及其左右侧差异记载的人类演化、人群差异及生存活动的重要信息一直为古人类学研究所关注。多年来, 对股骨断面的研究通常采用破坏性地切割或者制作模型的方法。本文利用三维激光表面扫描技术, 无损、快捷、方便地获取了20对现代中国人左右侧股骨外轮廓的三维数据, 采用CAD软件及几何形态测量方法对两侧股骨断面轮廓的大小及形状进行了对比和分析。初步研究结果发现: 两侧股骨的横断面相对面积差异极其显著, 绝对面积差异不显著, 不对称方式表现为波动不对称性, 而不是偏向不对称性; 个体之间两侧股骨横断面外轮廓形状的波动不对称性极其显著, 偏向不对称性虽有差异但不显著; 平均形状和面积分析结果似乎表明股骨稍有偏左侧优势。虽然本文所采用的标本量有限, 所得出的结论需要更多标本的进一步验证, 但是, 本文的研究结果提示利用三维激光扫描技术获取股骨横断面外轮廓数据, 并采用形态测量方法分析确实能够揭示出一些以往研究方法不能发现的重要信息, 这种研究骨骼不对称性的新方法值得进一步的应用。     

Is clutch size in birds affected by environmental conditions during growth?

Only environmental conditions occurring at the time of breeding have been shown to affect clutch size in birds, even though conditions experienced during growth are known to affect body size or egg size. We show here that environmental conditions experienced during early life can affect clutch size in captive zebra finches (Taeniopygia guttata) and wild great tits (Parus major). Not only do factors outside the immediate breeding season affect clutch size, but clutch size control mechanism is permanently influenced by conditions experienced during ontogeny.     

Physiological and anatomical changes during the early ontogeny of the heteroblastic bromeliad, Vriesea sanguinolenta, do not concur with the morphological change from atmospheric to tank form

Two distinct morphological forms characterize the ontogeny of many epiphytic bromeliads. Smaller plants exhibit an atmospheric habit, while larger plants form water‐impounding tanks. The study of the functional significance of heteroblasty in epiphytes is severely hampered by considerable size‐related variation in morphological, anatomical and physiological parameters. To overcome this problem, plants of varying size of both atmospheric and tank form were included in the present study with Vriesea sanguinolenta. The results show that virtually all morphological, anatomical and physiological characteristics vary during ontogeny, but changes were rarely directly related to the step change in gross morphology. Changes were either: (1) gradual from smallest atmospheric to small tank (e.g. leaf divergence angles, reduction in photosystem II efficiency during drought, speed of recovery after drought); (2) there was no change between atmospheric and small tank, but a gradual or step change within the tank form (stomatal density, relationship of leaf N and specific leaf area); or (3) developmental patterns were more complicated with decreases and increases during ontogeny (photosynthetic capacity, carbon isotope ratios, abscisic acid levels during drought). Although the comparisons between ontogenetic phases were always confounded by size differences, a hypothetical small tank plant is expected to suffer higher water loss than a real atmospheric, whereas a hypothetical, large atmospheric plant would show reduced access to resources, such as nutrients, in comparison with the real tank. The present results are consistent with the notion of heteroblasty as an adaptation of early ontogenetic stages to drought, but highlight that size‐related variation greatly modifies any difference directly associated with the step change from atmospheric to tank.     

Critical ages and stages of puberty in the accumulation of spinal and femoral bone mass: the validity of bone mass measurements

In growing children, lumbar and femoral areal bone mineral density (aBMD), as measured by dual-energy X-ray absorptiometry (DXA), is influenced by skeletal growth and bone size. Correction of lumbar bone mineral density (BMD) for bone volume (volumetric BMD [vBMD]), by the use of mathematical extrapolations, reduces the confounding effect of bone size, but vBMD remains dependent on age and bone size during growth. Femoral (neck and mid-shaft) vBMD, assessed by DXA, is independent of age prior to puberty, but a slight increase occurs in late puberty and after menarche. Femoral (mid-shaft) cortical bone density and radial cortical and trabecular bone densities, assessed by quantitative computed tomography (QCT), show no peak during childhood or adolescence. Bone strength index, calculated by peripheral QCT, increases with age and correlates with handgrip strength, bone cross-sectional area and cortical area. Puberty is one of the main factors that influences lumbar bone mineral content and aBMD accumulation, but a high incidence of fractures occurs during this period of life, which may be associated with a reduced aBMD.     

The place of Neandertals in the evolution of hominid patterns of growth and development

This study uses the two developmental fields of dental maturation and femoral growth to determine if the pattern of growth and development in Neandertals (archaic Homo sapiens) was intermediate between that of Homo erectus and recent modern humans. Specimens used in the analysis included Neandertals and Upper Palaeolithic early modern Homo sapiens from Europe and individuals from two recent modern human populations. Ontogenetic data for the H. erectus adolescent KNM-WT 15000 and for Gorilla gorilla were included for comparison. Previous reports have indicated that H. erectus demonstrates a pattern of ontogeny characterized by earlier and more rapid linear growth than in modern humans. Results reported here demonstrate that Upper Paleolithic early modern Homo sapiens display a growth trajectory indistinguishable from that of recent modern humans. The pattern of Neandertal ontogeny is not intermediate between the pattern displayed in H. erectus and the derived pattern seen in the modern reference samples and the early modern H. sapiens sample. The Neandertal growth trajectory is consistent with either slow linear growth or advanced dental development.     

Long bone histology of Chersina angulata : Interelement variation and life history data

The current study deduced the growth pattern and lifestyle habits of Chersina angulata based on bone histology and cross-sectional geometry of limb bones. Femora, humeri, and tibiae of seven different-sized individuals representing different ontogenetic stages were assessed to determine the interelement and intraskeletal histological variation within and among the tortoises. The bone histology of adult propodials consists of a highly vascularized, uninterrupted fibrolamellar bone tissue with a woven texture in the perimedullary and midcortical regions suggesting overall fast early growth. However, later in ontogeny, growth was slow and even ceased periodically as suggested by slowly formed parallel-fibered bone tissue and several growth marks in the pericortical region. In juvenile individuals, fibrolamellar bone tissue is restricted to the perimedullary regions of propodials as remnants of bone formed during the earliest stages of ontogeny. The epipodials are characterized by having parallel-fibered bone tissue present in their cortices; however, periodic arrests in growth are recorded at various times. Remnants of fibrolamellar bone tissue formed during early ontogeny occur in the epipodials of only a few individuals. Interelement variation is evident, in terms of variation in the orientation of vascular canals between individuals and within the same diaphyseal cross-sections. Different elements show varying cross-sectional geometry, which appear to be correlated with the fossorial behavior of the species. Our results show that of all the long bones, the tibia is least remodeled during ontogeny and it is therefore the best element for skeletochronology.     

Osteohistology of the non-mammaliaform traversodontids Protuberum cabralense and Exaeretodon riograndensis from southern Brazil

Abstract

The current study presents a detailed analysis of the osteohistology of the Triassic non-mammaliaform traversodontid cynodonts Protuberum cabralense and Exaeretodon riograndesis. The data provided here adds new information on the growth patterns of South American traversodontids. A single subadult individual of P. cabralense revealed bone tissues comprising uninterrupted fibrolamellar bone. Patches of slower growing lamellar bone at the periphery of one of the elements suggests a transition to overall slower growth in later ontogeny. The bone tissues of E. riograndensis also exhibit uninterrupted fibrolamellar bone during early ontogeny, but growth became cyclical from mid-ontogeny. The early rapid, sustained growth observed in these taxa is similar to that seen in other traversodontids, and may be related to the achievement of large body size in the derived members of the clade.     

Trophic niche ontogeny and palaeoecology of early Toarcian Stenopterygius (Reptilia: Ichthyosauria)

Reconstructing ecological niche shifts during ontogeny in extinct animals with no living analogues is difficult without exceptional fossil collections. Here we demonstrate how a previously identified ontogenetic shift in the size and shape of the dentition in the early Toarcian ichthyosaur Stenopterygius quadriscissus accurately predicts a particular dietary shift. The smallest S. quadriscissus fed on small, burst‐swimming fishes, with a steady shift towards faster moving fish and cephalopods with increasing body size. Larger adult specimens appear to have been completely reliant on cephalopods, with fish completely absent from gut contents shortly after onset of sexual maturity. This is consistent with a previously proposed ontogenetic niche shift based on tooth shape and body size, corroborating the idea that dental ontogeny may be a useful predictor of dietary shifts in marine reptiles. Applying the theoretical framework used here to other extinct species will improve the resolution of palaeoecological reconstructions, where appropriate sample sizes exist.     

A Shared Pattern of Postnatal Endocranial Development in Extant Hominoids

By comparing species-specific developmental patterns, we can approach the question of how development shapes adult morphology and contributes to the evolution of novel forms. Studies of evolutionary changes to brain development in primates can provide important clues about the emergence of human cognition, but are hindered by the lack of preserved neural tissue in the fossil record. As a proxy, we study the shape of endocasts, virtual imprints of the endocranial cavity, using 3D geometric morphometrics. We have previously demonstrated that the pattern of endocranial shape development is shared by modern humans, chimpanzees and Neanderthals after the first year of life until adulthood. However, whether this represents a common hominoid mode of development is unknown. Here, we present the first characterization and comparison of ontogenetic endocranial shape changes in a cross-sectional sample of modern humans, chimpanzees, gorillas, orangutans and gibbons. Using developmental simulations, we demonstrate that from late infancy to adulthood ontogenetic trajectories are similar among all hominoid species, but differ in the amount of shape change. Furthermore, we show that during early ontogeny gorillas undergo more pronounced shape changes along this shared trajectory than do chimpanzees, indicative of a dissociation of size and shape change. As shape differences between species are apparent in even our youngest samples, our results indicate that the ontogenetic trajectories of extant hominoids diverged at an earlier stage of ontogeny but subsequently converge following the eruption of the deciduous dentition.     

Automated measurement of neural foramen cross-sectional area during in vivo functional movement

An automated technique to measure neural foramen cross-sectional area during in vivo, multi-planar movements is presented. This method combines three-dimensional (3D) models of each vertebra obtained from CT scans with in vivo movement data collected using high-speed biplane radiography. A novel computer algorithm that automatically traces a path around the bony boundary that defines the neural foramen at every frame of X-ray data is described. After identifying the neural foramen boundary, the cross-sectional area is calculated. The technique is demonstrated using data collected from a patient with cervical radiculopathy who is tested before and after conservative treatment. The technique presented here can be applied when 3D, dynamic, functional movements are performed. Neural foramen cross-sectional area can be quantified at specific angles of intervertebral rotation, allowing for matched comparisons between two trials or two test sessions. The present technique is ideal for longitudinal studies involving subjects who receive conservative or surgical treatments that may affect spine motion.     

Observation on intranuclear crystal and nucleolar size at different stages of cell differentiation in the midgut epithelium of several insects.

Based on an inverse size relationship between nuclear crystal and nucleolus in different cells it has been postulated by several authors that the crystal develops from nucleolar materials. The purpose of the present paper is to investigate the validity of this argument. Intranuclear proteinaceous crystals appear in differentiating midgut cells of Gyrinus marinus and Tenebrio molitor. In an autoradiographic study we have previously demonstrated in these two species that the crystals do not develop from nucleolar materials. However, an inverse relationship with regard to size is observed between these 2 structures during the cell differentiation: the cross-sectional area of the nucleolus decreases when the cross-sectional area of the crystal increases. But a decrease in size of the nucleolus is also observed during the differentiation of the midgut cells of Gyrinus natator where the crystals are not present. Consequently an inverse size relationship cannot be a sufficient argument to postulate that intranuclear crystals and nucleoli are interconvertible structures; decrease in size of the nucleolus is not related to development of the intranuclear crystal.     

Femoral curvature in Neanderthals and modern humans: a 3D geometric morphometric analysis

Since their discovery, Neanderthals have been described as having a marked degree of anteroposterior curvature of the femoral shaft. Although initially believed to be pathological, subsequent discoveries of Neanderthal remains lead femoral curvature to be considered as a derived Neanderthal feature. A recent study on Neanderthals and middle and early Upper Palaeolithic modern humans found no differences in femoral curvature, but did not consider size-corrected curvature. Therefore, the objectives of this study were to use 3D morphometric landmark and semi-landmark analysis to quantify relative femoral curvature in Neanderthals, Upper Palaeolithic and recent modern humans, and to compare adult bone curvature as part of the overall femoral morphology among these populations.Comparisons among populations were made using geometric morphometrics (3D landmarks) and standard multivariate methods. Comparative material involved all available complete femora from Neanderthal and Upper Palaeolithic modern human, archaeological (Mesolithic, Neolithic, Medieval) and recent human populations representing a wide geographical and lifestyle range. There are significant differences in the anatomy of the femur between Neanderthals and modern humans. Neanderthals have more curved femora than modern humans. Early modern humans are most similar to recent modern humans in their anatomy. Femoral curvature is a good indicator of activity level and habitual loading of the lower limb, indicating higher activity levels in Neanderthals than modern humans. These differences contradict robusticity studies and the archaeological record, and would suggest that femoral morphology, and curvature in particular, in Neanderthals may not be explained by adult behavior alone and could be the result of genetic drift, natural selection or differences in behavior during ontogeny.     

Variation in Vertebral Number in Galaxiid Fishes,How Fishes Swim and a Possible Reason for Pleomerism

The number of vertebrae in fishes is widely variable, with this variation having connections to phyletic position, geography, various environmental factors such as temperature and salinity, biome occupied and life history pattern. Variation is sometimes a response to environment, sometimes explicitly adaptive and probably often both. Swimming mode is likely to be influenced by body flexibility, which in turn is influenced by vertebral counts. Since vertebral number is fixed early in ontogeny, there is a predictive element in the choice of vertebral number during development that affects later adaptiveness. Pleomerism, the relationship between vertebral number and body size across the diversity of fishes, may be driven by the square/cube relationships between length, cross-sectional area and volume. Pleomerism in diadromous galaxiid fishes probably reflects adaptive advantages achieved during marine juvenile life and in non-diadromous species may reflect the size at which mid-water, shoaling juveniles become to benthic, cryptic, within-substrate behaviours.     

Dentition and histology in titanosaurian dinosaur embryos from Upper Cretaceous of Patagonia,Argentina

Abstract: Exceptionally preserved sauropod embryos from the Late Cretaceous Anacleto Formation in Auca Mahuevo (Neuquén Province, Argentina) have provided fundamental information on titanosaurian ontogeny. This paper describes the dental composition, disposition and microstructure of the specimens. Embryonic teeth show size disparity, with lengths that vary from 1 to 3 mm and diameters ranging from 0.15 to 0.26 mm, with the most frequent length values between 2.5 and 3 mm. Apparently, a typical ‘pencil‐like’ tooth morphology and a dental formula of Pm 4, M 7–8/D10? remained constant during titanosaurian ontogeny, whereas the arrangement of teeth in the skull shows notable ontogenetic changes. Absence of wear facets on teeth suggests a lack of prenatal chewing movements. The enamel proportion is significantly higher in embryos than in mature titanosaurs, which suggests that this relationship varies during ontogeny. Embryonic bony tissue is composed of highly vascularized, cellular woven bone. The absence of osteonal tissue, the high degree of vascularization, the presence of numerous osteocytes and poor development of periosteal bone reveals that the Auca Mahuevo titanosaurs would have had a high early growth rate and that they were buried at a relatively advanced embryonic stage.     

Automated measurement of neural foramen cross-sectional area during in vivo functional movement

An automated technique to measure neural foramen cross-sectional area during in vivo, multi-planar movements is presented. This method combines three-dimensional (3D) models of each vertebra obtained from CT scans with in vivo movement data collected using high-speed biplane radiography. A novel computer algorithm that automatically traces a path around the bony boundary that defines the neural foramen at every frame of X-ray data is described. After identifying the neural foramen boundary, the cross-sectional area is calculated. The technique is demonstrated using data collected from a patient with cervical radiculopathy who is tested before and after conservative treatment. The technique presented here can be applied when 3D, dynamic, functional movements are performed. Neural foramen cross-sectional area can be quantified at specific angles of intervertebral rotation, allowing for matched comparisons between two trials or two test sessions. The present technique is ideal for longitudinal studies involving subjects who receive conservative or surgical treatments that may affect spine motion.     

Biomechanics of the hip and birth in early Homo

A complex of traits in the femur and pelvis of Homo ereclus and early “erectus-like” specimens has been described, but never satisfactorily explained. Here the functional relationships between pelvic and femoral structure in humans are explored using both theoretical biomechanical models and empirical tests within modern samples of diverse body form (Pecos Amerindians, East Africans). Results indicate that a long femoral neck increases mediolateral bending of the femoral diaphysis and decreases gluteal abductor and hip joint reaction forces. Increasing biacetabular breadth along with femoral neck length further increases M-L bending of the femoral shaft and maintains abductor and joint reaction forces at near “normal” levels. When compared to modern humans, Homo erectus and early “erectus-like” specimens are characterized by a long femoral neck and greatly increased M-L relative to A-P bending strength of the femoral shaft, coupled with no decrease in hip joint size and a probable increase in abductor force relative to body size. All of this strongly suggests that biacetabular breadth as well as femoral neck length was relatively large in early Homo. Several features preserved in early Homo partial hip bones also indicate that the true (lower) pelvis was very M-L broad, as well as A-P narrow. This is similar to the lower pelvic shape of australopithecines and suggests that nonrotational birth, in which the newborn's head is oriented transversely through the pelvic outlet, characterized early Homo as well as Australopithecus. Because M-L breadth of the pelvis is constrained by other factors, this may have limited increases in cranial capacity within Homo until rotational birth was established during the late Middle Pleistocene. During or after the transition to rotational birth biacetabular breadth decreased, reducing the body weight moment arm about the hip and allowing femoral neck length (abductor moment arm) to also decrease, both of which reduced M-L bending of the proximal femoral shaft. Variation in femoral structural properties within early Homo and other East African Early Pleistocene specimens has several taxonomic and phylogenetic implications. © 1995 Wiley-Liss, Inc.     

Ontogenetic transition in leaf traits: a new cost associated with the increase in leaf longevity

Aims Recent work has identified a worldwide 'economics' spectrum of correlated leaf traits that mainly reflects the compromises between maximizing leaf longevity and short-term productivity. However, during the early stages of tree growth different species tend to exhibit a common strategy, because competition for soil water and nutrients forces the maximization of short-term productivity owing to the need for rapid growth during the most vulnerable part of the tree's life cycle. Accordingly, our aim here was to compare the variations that occur during ontogeny in the different leaf traits (morphology and leaf chemical composition) of several coexisting Mediterranean woody species differing in their leaf life spans and to test our hypothesis that tree species with a long leaf life span should exhibit larger shifts in leaf characteristics along ontogeny.Methods Six Mediterranean tree species differing in leaf life span, selected from three plots located in central-western Spain, were studied during three growth stages: seedlings, juveniles and mature trees. Leaf life span, leaf morphology (leaf area, dry weight, thickness and mass per unit area) and chemical composition (N and fibre concentrations) were measured in all six species. The magnitude of the ontogenetic changes in the different traits was estimated and related to the mean leaf longevity of the different species.Important findings Along ontogeny, strong changes were observed in all variables analysed. The early growth stages showed lower leaf thickness, leaf thickness and mass per unit area and N, cellulose and hemicellulose concentrations than mature trees, but a higher lignin content. However, these changes were especially marked in species with a longer leaf life span at maturity. Interspecific differences in leaf life span, leaf morphology and chemical composition were stronger at the mature stage than at the seedling stage. We conclude that greater plasticity and more intense strategy shifts along ontogeny are necessarily associated with long leaf life span. Our results thus provide a new aspect that should be incorporated into the analysis of the costs and benefits associated with the different strategies related to leaf persistence displayed by the different species. Accordingly, the intensity of the alterations in leaf traits among different growth stages should be added to the suite of traits that change along the leaf economics spectrum.     

A 3-D geometric morphometric study of intraspecific variation in the ontogeny of the temporal bone in modern Homo sapiens

This study addresses how the human temporal bone develops the population-specific pattern of morphology observed among adults and at what point in ontogeny those patterns arise. Three-dimensional temporal bone shape was captured using 15 landmarks on ontogenetic series of specimens from seven modern human populations. Discriminant function analysis revealed that population-specific temporal bone morphology is evident early in ontogeny, with significant shape differences among many human populations apparent prior to the eruption of the first molar. As early as five years of age, temporal bone shape reflects population history and can be used to reliably sort populations, although those in closer geographic proximity and molecular affinity are more likely to be misclassified. The deviation of cold-adapted populations from this general pattern of congruence between temporal bone morphology and genetic distances, identified in previous work, was confirmed here in adult and subadult specimens, and was revealed to occur earlier in ontogeny than previously recognized. Significant differences exist between the ontogenetic trajectories of some pairs of populations, but not among others, and the angles of these trajectories do not reflect genetic relationships or final adult temporal bone size. Significant intrapopulation differences are evident early in ontogeny, with differences becoming amplified by divergent trajectories in some groups. These findings elucidate how the congruence between adult human temporal bone morphology and population history develops, and reveal that this pattern corresponds closely to that described previously for facial ontogeny.     

Ontogenetic adaptation to bipedalism: age changes in femoral to humeral length and strength proportions in humans, with a comparison to baboons

The increase in lower/upper limb bone length and strength proportions in adult humans compared to most other anthropoid primates is commonly viewed as an adaptation to bipedalism. The ontogenetic development of femoral to humeral proportions is examined here using a longitudinal sample of 20 individuals measured radiographically at semiannual or annual intervals from 6 months of age to late adolescence (a subset of the Denver Growth Study sample). Anthropometric data (body weights, muscle breadths) were also available at each examination age. Results show that while femoral/humeral length proportions close to those of adults are already present in human infants, characteristically human femoral/humeral diaphyseal strength proportions only develop after the adoption of bipedalism at about 1 year of age. A rapid increase in femoral/humeral strength occurs between 1 and 3 years, followed by a slow increase until mid-late adolescence, when adult proportions are reached. When age changes in material properties are factored in, femoral strength shows an almost constant relationship to body size (body mass.bone length) after 5 years of age, while humeral strength shows a progressive decline relative to body size. Femoral/humeral length proportions increase slightly throughout growth, with no apparent change in growth trajectory at the initiation of walking, and with a small decline in late adolescence due to later growth in length of the humerus. A sex difference in femoral/humeral strength proportions (females greater) but not length proportions, develops early in childhood. Thus, growth trajectories in length and strength proportions are largely independent, with strength proportions more responsive to actual changes in mechanical loading. A cross-sectional ontogenetic sample of baboons (n=30) illustrates contrasting patterns of growth, with much smaller age changes in proportions, particularly strength proportions, although there is some indication of an adaptation to altered limb loadings early in baboon development.