Effects of suboccipital release with craniocervical flexion exercise on craniocervical alignment and extrinsic cervical muscle activity in subjects with forward head posture

BackgroundForward head posture is a head-on-trunk malalignment, which results in musculoskeletal dysfunction and neck pain. To improve forward head posture, both the craniocervical flexion exercise and the suboccipital release technique have been used. Objectives: The purpose of this study was to compare the immediate effects of craniocervical flexion exercise and suboccipital release combined with craniocervical flexion exercise on craniovertebral angle, cervical flexion and extension range of motion, and the muscle activities of the sternocleidomastoid, anterior scalene, and splenius capitis during craniocervical flexion exercise in subjects with forward head posture.MethodsIn total, 19 subjects (7 males, 12 females) with forward head posture were recruited using G-power software. Each subject performed craniocervical flexion exercise and suboccipital release combined with craniocervical flexion exercise in random order. After one intervention was performed, the subject took a 20 min wash out period to minimize any carry-over effect between interventions. Craniovertebral angle, cervical flexion and extension range of motion, and the muscle activities of the sternocleidomastoid, anterior scalene, and splenius capitis were measured. A one-way, repeated-measures ANOVA was used to assess differences between the effects of the craniocervical flexion exercise and suboccipital release combined with craniocervical flexion exercise interventions in the same group.ResultsCraniovertebral angle (p < 0.05), cervical flexion range of motion (p < 0.05), and cervical extension range of motion (p < 0.001) were significantly greater after suboccipital release combined with craniocervical flexion exercise compared to craniocervical flexion exercise alone. The muscle activities of the sternocleidomastoid, anterior scalene, and splenius capitis were significantly lower during suboccipital release combined with craniocervical flexion exercise than during craniocervical flexion exercise alone across all craniocervical flexion exercise phases except the first (all p < 0.05).ConclusionThe addition of suboccipital release to craniocervical flexion exercise provided superior benefits relative to craniocervical flexion exercise alone as an intervention for subjects with forward head posture.     

Head posture and craniofacial morphology

The associations between craniofacial morphology and the posture of the head and the cervical column were examined in a sample of 120 Danish male students aged 22–30 years. Two head positions were recorded on lateral cephalometric radiographs, one determined by the subject's own feeling of a natural head balance (self balance position), and the other by the subject looking straight into a mirror (mirror position). Craniofacial morphology was described by 42 linear and angular variables, and postural relationships by 18 angular variables. A comprehensive set of correlations was found between craniofacial morphology and head posture. The correlations were similar for both head positions investigated. Of the postural variables, the position of the head in relation to the cervical column showed the largest set of correlations with craniofacial morphology. Extension of the head in relation to the cervical column was found in connection with large anterior and small posterior facial heights, small antero-posterior craniofacial dimensions, large inclination of the mandible to the anterior cranial base and to the nasal plane, facial retrognathism, a large cranial base angle, and a small nasopharyngeal space. The possible role of functional factors in mediating the relationship between morphology and posture was discussed.     

Comparative craniofacial variation in Navajo Indians and North American Caucasians

Landmarks digitized from lateral cephalometric radiographs of 107 Navajo Indians between 10 and 12 years of age were analyzed to determine coefficients of variation or standard deviations for 38 cephalometric measurements. These values were compared with the same measures of variation for identical measurements on North American whites derived from the Michigan and Philadelphia Growth Studies. For the majority of variables, there were no differences between groups. Variation for the genetically and environmentally isolated Navajo Indians was the same as that of the highly diverse Caucasian samples. However, measurements of upper, lower, and total anterior facial height (N-ANS, ANS-Me, and N-Me, respectively) indicate that these features are substantially less variable in Navajo Indians relative to the Michigan and Philadelphia populations.     

Craniocervical morphology and posture in Australian aboriginals

The length of the spinal column as a percentage of stature is smaller in the Australian aboriginal than in most other ethnic groups (Abbie, 1957). It is conceivable that relative lengths of the cervical column might influence population differences in craniocervical posture and craniofacial morphology. The present study aimed to elucidate this relationship by comparing head posture and craniofacial morphology in Australian aboriginals to the same features in a previously studied sample of 120 Danish students (Solow and Tallgren, 1976). The aboriginal sample consisted of 42 young male adults from the Yuendumu settlement, Northern Territory, Australia. Cephalometric films of the natural head position were taken during a field trip to the settlement. The comparison comprised 18 postural and 61 morphological variables. In the aboriginals, the cervical column was shorter and had a less pronounced lordosis. The head was held about 3° lower, and the upper cervical column was 81/2° more forward inclined. As a consequence, the craniocervical angle was about 6° larger. Comparison of the craniofacial morphology in the two groups showed in the aboriginals a shorter upper facial height, a larger anterior lower facial height, and a larger vertical jaw relationship (NL/ML). The length of the posterior cranial base, s-ba, was 4 mm shorter (P <0.001) in the aboriginals, possibly developmentally related to the generally shorter spinal column in Australian aboriginals.     

Forward head posture is associated with pressure pain threshold and neck pain duration in university students with subclinical neck pain

Abstract

Objective: The aims of this study are to investigate the association between: (i) forward head posture (FHP) and pressure pain thresholds (PPTs); (ii) FHP and maladaptive cognitive processes; and (iii) FHP and neck pain characteristics in university students with subclinical neck pain.

Materials/methods: A total of 140 university students, 90 asymptomatic and 50 with subclinical neck pain, entered the study. Demographic data, anthropometric data, FHP, and PPTs were collected for both groups. In addition, pain characteristics, pain catastrophizing, and fear of movement were assessed for participants with neck pain. FHP was characterized by the angle between C7, the tragus of the ear, and the horizontal line. Correlation analysis and multivariate regression analysis were conducted.

Results: Participants with subclinical neck pain showed significantly lower PPTs than participants without neck pain (p?<?.05), but similar FHP (p?>?.05). No significant association was found between FHP and PPTs in the asymptomatic group. In the group of participants with subclinical neck pain, PPTs at the right trapezius and neck pain duration explained 19% of the variance of FHP (R²?=?0.23; adjusted R²?=?0.19; p?<?.05).

Conclusion: This study suggests that FHP is not associated with PPTs in asymptomatic university students. In university students with subclinical neck pain, increased FHP was associated with right trapezius hypoalgesia and with neck pain of shorter duration. These findings are in contrast with current assumptions on the association between neck pain and FHP.     

Geographic variation of wing morphology of great fruit‐eating bats (Artibeus lituratus): environmental,genetic and spatial correlates of phenotypic differences

Responses of species to environmental gradients are important and frequent determinants of geographic phenotypic variation that can drive adaptive processes. Nonetheless, random genetic processes such as drift can also result in geographic variation in phenotypes, and should be evaluated before implicating selection as the process driving phenotypic change. We examined geographic variation in wing morphology of Artibeus lituratus among 18 different sites distributed across interior Atlantic Forest of Paraguay and Argentina. Moreover, we contrasted geographic variation with environmental, spatial, and genetic variation to test hypotheses related to selection and drift and their impacts on wing morphology. For A. lituratus distributed across interior Atlantic Forest, significant differences among sites characterized variation in wing morphology. Geographic variation was significantly related to climatic variables but not spatial or genetic distances. Such a pattern suggests that phenotypic variation is related to selection for particular environmental regimes, and not genetic drift. Four significant dimensions of phenotypic variation were determined. Three dimensions were related to variation among individuals in terms of wing tips, whereas one was related to overall body size. Wing tips are important for manoeuverability during flight and differences among sites likely reflect differences in forest and vegetation structure that must be managed during foraging. Although climate provides good surrogates for environmental variation, it is probably only an indirect cue of selection regimes that determine variation in wing morphology. Future studies should evaluate more direct environmental measures such as vegetation structure when attempting to interpret geographical variation in wing morphology.     

农林复合系统中滇龙胆形态和生物量变化研究

以幼龄茶树(Camellia sinensis var.sinensis)、十年茶树、木瓜(Chaenomeles sinensis)、尼泊尔桤木(Alnus nepalensis)、大叶桉(Eucalyptus robusta)间作模式和荒坡栽培滇龙胆为研究对象,测定其株高、茎粗、叶长、根粗、生物量等性状,采用单因素方差分析、多重比较、相关性分析和多元逐步回归分析对其形态和生物量数据进行分析。结果表明:荒坡栽培、滇龙胆与十年茶树间作其株高最高,为(37.32±8.36)cm和(37.31±9.62)cm,与大叶桉间作其株高最低,为(19.08±12.40)cm;荒坡栽培植株茎粗数值最高,为(0.36±0.13)cm,大叶桉间作茎粗数值最低,为(0.23±0.04)cm;与茶树间作植株根系最长,为(18.42±7.23)cm和(17.71±7.34)cm,与尼泊尔桤木间作植株须根数最少,为(7.32±2.23)cm;根粗受栽培模式影响不显著(P0.05);荒坡栽培全株生物量最高,为(14.52±13.37)g,大叶桉间作全株生物量最低,为(2.17±1.42)g。相关性分析显示,株高、茎粗和须根数与全株生物量呈极显著的正相关(R=0.514,P0.01;R=0.510,P0.01;R=0.339,P0.01)。根茎比与全株生物量呈极显著的负相关(R=-0.295,P0.01)。多元逐步回归分析显示,各性状对全株生物量的积累贡献程度不同,株高、茎粗、须根数和根粗是影响滇龙胆生物量积累的主要性状。荒坡栽培光照条件较好,有利于植株生物量的积累;与桉树间作,滇龙胆可能受生物与非生物胁迫的共同影响,使其植株矮小,生物量偏低。6种栽培模式中荒坡、滇龙胆与茶树、木瓜间作栽培为高产模式。研究结果可为农林药用复合种植中物种搭配、时间和空间种植技术优化升级以及管理提供理论依据。     

Head morphology in perinatal dolphins: a window into phylogeny and ontogeny

In this paper on the ontogenesis and evolutionary biology of odontocete cetaceans (toothed whales), we investigate the head morphology of three perinatal pantropical spotted dolphins (Stenella attenuata) with the following methods: computer-assisted tomography, magnetic resonance imaging, conventional X-ray imaging, cryo-sectioning as well as gross dissection. Comparison of these anatomical methods reveals that for a complete structural analysis, a combination of modern imaging techniques and conventional morphological methods is needed. In addition to the perinatal dolphins, we include series of microslides of fetal odontocetes (S. attenuata, common dolphin Delphinus delphis, narwhal Monodon monoceros). In contrast to other mammals, newborn cetaceans represent an extremely precocial state of development correlated to the fact that they have to swim and surface immediately after birth. Accordingly, the morphology of the perinatal dolphin head is very similar to that of the adult. Comparison with early fetal stages of dolphins shows that the ontogenetic change from the general mammalian bauplan to cetacean organization was characterized by profound morphological transformations of the relevant organ systems and roughly seems to parallel the phylogenetic transition from terrestrial ancestors to modern odontocetes.     

Size and shape variability in relation to species differences and climatic gradients in the African rodent Oenomys

Aim The modern African murine rodent Oenomys is a semiarboreal genus characteristic of the rain forest zone. The size and shape geographical differentiation is studied in order to discuss the possible evolutionary patterns and constraints leading to this distribution. Location Two species of Oenomys have been previously recognized, corresponding to the West African forest block on the one hand and to the main forest block on the other hand. Both species have been sampled, and forty localities permit the study of the whole geographical range of Oenomys, from Guinea to Kenya. Methods A Fourier analysis applied to the outlines of the first upper and lower molars allows a quantification of the size and shape variations across the geographical range of Oenomys. Results This morphometrical analysis defines three morphological groups of Oenomys, corresponding to the West, Central, and East African forest zone. This result suggests the existence of an additional cryptic species. The Western group is characterized by broad asymmetrical molars and a small size. The Central African group has more elongated and larger molars while the Eastern African group displays extremely constricted molars and a small size. Main conclusion The shape can be considered as charactheristic of each group and its variations appear to be mostly related to phylogeny while size exhibits variations within each group related to climatic gradients. This discrepancy could be related to different genetic determinants for both characters, the shape being strongly genetically constrained while size can vary according to a wide range of environmental factors.     

Butterfly wing morphology variation in the British Isles: the influence of climate, behavioural posture and the hostplant-habitat

Gradients (isophenes) in modifications of butterfly wing morphology (colour, pattern, size) to the north and west of Britain are shown to correlate closely with contemporary environmental gradients, whereas their alleged formation as infra-specific units in Devensian refugia off western Britain is unsubstantiated. A model is described which explains the transformation in phenotypes in relationship to climate, especially ambient temperatures and radiation levels. In cooler, less predictable summer conditions to the north and west, selection has favoured modifications in adult phenotypes that maintain efficiency in thermoregulation, mate advertisement and predator escape. The form that wing modifications take depends mainly on basking posture (lateral, dorsal-absorption and reflectance), which determines the allocation and interaction of functions on different wing surfaces. It is also dependent on hostplant-habitat structure, which influences thermal stability and the milieu of predators and conspecifics, and other behavioural norms (mate-locating behaviour) and biological attributes (size, robustness, speed and mode of flight, chemical defences) which affect their relationships with predators and conspecifics. The significance of Quaternary palaeoenvironments to phenetic transformations is discussed as is the relevance of the model to the development of phenotypes in arctic endemic butterflies. Differences in phenotypes of butterflies which occupy arctic and temperate montane environments are also predicted by the model.     

五种蝙蝠形态与回声定位叫声的性别差异

为研究角菊头蝠(Rhinolophus cornutus)、三叶蹄蝠(Aselliscus uheeleri)、大蹄蝠(Hipposideros armiger)、大鼠耳蝠(Myotis myotis)和大足鼠耳蝠(M．riketti)的形态和回声定位叫声的性别差异性,明确同种蝙蝠雌雄个体对食物、栖息地等资源利用的细微差异,我们利用超声波探测仪、Batsound分析软件及SPSS11．0统计软件对5种95只蝙蝠进行了录音、声波分析和统计分析。5种蝙蝠形态性别差异性不显著,角菊头蝠、三叶蹄蝠、大蹄蝠和大足鼠耳蝠叫声频率性别差异性显著,大鼠耳蝠叫声频率性别差异性不显著。角菊头蝠雌性叫声的基频、分音、主频率高于雄性,声脉冲时间、间隔时间大于雄性,调频(FM)带宽小于雄性;三叶蹄蝠、大蹄蝠叫声的基频、主频率雄性高于雌性,调频带宽雌性小于雄性;大足鼠耳蝠叫声的主频率雄性高于雌性,FM带宽雌性大于雄性[动物学报49(6)：742～747,2003]。     

Genotypic variation in drought response of silver birch (Betula pendula Roth): leaf and root morphology and carbon partitioning

This study investigates the drought response of four genotypes of Betula pendula with a focus on leaf and root morphological traits, leaf phenology and carbon partitioning between shoot and root. Potted one-year-old clonal plants of four genotypes from regions with low to high annual rainfall (550–1270 mm year⁻¹) were subjected to drought periods of 12–14 weeks in two subsequent years. Well-watered control plants of the four genotypes differed significantly with respect to total leaf area per plant (LA) and specific leaf area (SLA), whereas differences in total fine root surface area (RA), root specific area (SRA), and the fine root:leaf mass ratio (FR:LM) were not significant. Highest LA and SLA were found in the clone originating from the driest environment. In complementary physiological investigations this clone was found to have the highest water use as well which was interpreted as competitive superiority in terms of water consumption. Drought resulted in an increase in SLA in all genotypes, and a decrease in LA. Leaf area reduction was more pronounced in the genotypes from high than in those from low rainfall origin. The ratio of total root to leaf surfaces remained more or less constant after drought application despite an increase in FR:LM. This is explained by a decrease in SRA resulting from a reduced abundance of very small fine rootlets (diameter <0.2 mm) in the drought-treated plants. The loss in total root surface area due to a reduction in finest root mass was compensated for by a relative increase in total root dry mass per plant. Comparison of results from the first and second drought period indicated a marked influence of timing of drought, root system size, and putative root limitation on plant drought response. We conclude that leaf and root morphology, the total leaf and root surfaces, and the morphological response to drought in birch are to a large extent under genetic control.     

Patterns of variation in wing morphology in the cactophilic Drosophila buzzatii and its sibling D. koepferae

Drosophila buzzatii and D. koepferae are two sibling species that breed on the necrotic tissues of several cactus species and show a certain degree of niche overlap. Also, they show differences in several life history traits, such as body size and developmental time, which probably evolved as a consequence of adaptation to different host plants. In this work we investigate the ecological and genetic factors affecting wing morphology variation both within and between species. Three wing traits were scored, distal and proximal wing length and width in isofemale lines reared in two of the most important host cacti: Opuntia sulphurea and Trichocereus terschekii. Our results revealed that differences between species and sexes in wing size and shape were significant, whereas the cactus factor was only significant for wing size. Intraspecific analyses showed that differences among isofemale lines were highly significant for both size and shape in both species, suggesting that an important fraction of variation in wing morphology has a genetic basis. Moreover, the line by cactus interaction, which can be interpreted as a genotype by environment interaction, also accounted for a significant proportion of variation. In summary, our study shows that wing size is phenotypically plastic and that populations of D. buzzatii and D. koepferae harbour substantial amounts of genetic variation for wing size and shape. Interspecific differences in wing size and shape are interpreted in terms of spatial predictability of the different host plants in nature.     

Correlated evolution of floral morphology and mating-type frequencies in a sexually polymorphic plant

In sexually polymorphic species, reproductive morphology governs mating patterns and the character of negative frequency-dependent selection. If local environmental conditions cause sexual morphs to differ between populations, then frequency-dependent selection should create corresponding geographic variation in morph frequencies. We investigate this relation with a model of morph-ratio evolution and analysis of geographic variation in the heterostylous plant Narcissus triandrus. Unlike other tristylous species, N. triandrus possesses both imperfect reciprocity among morphs in sex-organ position and a self-incompatibility system that permits outcrossing within and between morphs. We sampled 137 populations throughout the Iberian Peninsula for floral-morph ratios, and measured floral morphology in 31 populations. Morph ratios exhibited three atypical features: (1) predominance of the long-styled (L) morph; (2) absence of the mid-styled (M) morph from 17.5% of populations; and (3) a negative relation between the frequencies of the L and M morphs among populations. Morph ratios varied geographically, with decreasing frequency of the M morph from the southeast to the northwest of the species' range. Much of this variation accompanied allometric change in the positions of sex organs, especially the mid-level organs, with the M morph declining in frequency and ultimately being lost in large-flowered populations. Using multivariate multiple regression, we demonstrate that variation in floral morphology among populations predicts this geographic variation in morph frequencies. Our theoretical analysis illustrates that patterns of pollen transfer governed by imperfect sex-organ reciprocity can select for unequal equilibrium morph ratios like those observed for N. triandrus. We interpret the L-biased morph ratios and the unusual morphology of N. triandrus as a consequence of its atypical intramorph compatibility system.     

Growth,morphology and leaf characteristics after simulated herbivory in Chinese subtropical evergreen saplings

Growth, morphology and leaf characteristics were assessed in late spring following simulated autumnal defoliation in second-year saplings of three Chinese subtropical evergreen tree species.Castanopsis fargesii showed strong compensatory growth in terms of plant biomass after removal of both 50 and 75% of leaf biomass and slight compensatory growth after 90% defoliation. DefoliatedC. fargesii saplings had more leaves per unit shoot length than non-defoliated saplings. New leaves on defoliated plants were smaller and had higher per area nitrogen content than new leaves on non-defoliated plants.Pinus massoniana andElaeocarpus japonicus showed strong and no compensatory growth, respectively, after 50% defoliation. The strong compensatory growth inP. massoniana andC. fargesii may partly explain why these species predominate in the early and late successional phases of evergreen broad-leaved forests     

基于三维人脸模型及人工测量数据分析现代中国人群面部表型的性别差异

传统体质人类学研究中的样本采集方法是手工测量以及肉眼观察,采集过程中会存在较大的主观性,易产生误差,同时在采集大样本时费时费力。近年来,三维摄像系统被越来越多的应用于人脸分析,其优势是快速高效和准确,并且涵盖了传统测量方法无法精确获取的表型特征信息,可以更加细化地分析人脸表型特征和特征之间的相互关系。本研究探索性地基于三维人脸模型图像,利用曲率和邻域信息的点筛查方法定位了面部的一些关键测量点,建立一套简单、有效、准确率较高的三维人脸模型图像关键点定位方法,能较准确地定位98%以上的眼内角点和鼻尖点,并在此基础上确定了鼻根点、鼻下点、左右鼻翼点和鼻翼外侧最低点等其他面部关键点。并且还提出了在三维人脸模型图像基础上量化部分面部观察类表型特征,如鼻侧深度、鼻根高度、面部扁平度等,尝试性地将这些观察类性状转化为能够测量的性状,建立了一套可以计算的描述方法,具有一定的创新性。本研究还结合三维人脸模型提取数据和人工测量数据,探讨了现代中国人群(以江淮汉族为例)面部表型特征的性别差异,发现大多数面部表型特征在现代中国人群中都存在明显的男女性别差异,鼻侧深度、鼻根高度、面部扁平度的性别差异最为显著,其...     

Pollinators,floral morphology and scent chemistry in the southern African orchid genus Schizochilus

Floral evolution often involves suites of traits, including morphology, colour and scent, but these traits are seldom analysed together in comparative studies. We investigated the associations between floral traits and pollination systems in Schizochilus, a southern African orchid genus with small nectar-producing flowers that has not been studied previously with respect to pollination biology. Field observations indicated the presence of distinct pollination systems in the four species which occur in the Drakensberg, including pollination by muscid flies in Schizochilus angustifolius, tachinid flies in Schizochilus zeyheri, various small flies in Schizochilus bulbinella and bees and wasps in Schizochilus flexuosus. Pollination success and pollen transfer efficiency clearly differed among the four species but were not correlated with the quantity of nectar rewards. Multivariate analysis of floral morphology and floral scent chemistry based on GC-MS data revealed significant differences among species as well as populations within species. The floral scent of S. angustifolius was dominated by the benzenoid compounds benzaldehyde and phenylacetaldehyde. Samples of one population of S. bulbinella were relatively similar to S. angustifolius but samples of another population were very distinct due to the occurrence of the nitrogen-containing compounds 3-methyl-butyl aldoxime (syn/anti) and the higher amounts of aliphatic esters, alcohols and acids. In contrast, the floral scent of S. flexuosus and S. zeyheri was characterized by high relative amounts of methyl benzoate. We conclude that Schizochilus has distinct, specialized pollination systems associated with subtle but significant variation in floral morphology and scent chemistry. We also caution that sampling of several populations may be required to characterize floral scent composition at the species-level in plants.     

Latitudinal population differentiation in phenology,life history and flower morphology in the perennial herb Lythrum salicaria

Abstract In plants with a wide distribution, phenological characters can be expected to vary clinally along climatic gradients, whereas other characters important for adaptation to local biotic and abiotic factors may vary in a more mosaic fashion. We used common‐garden experiments and controlled crosses to examine population differentiation in phenology, life history and morphology in the perennial herb Lythrum salicaria along a latitudinal transect through Sweden (57°N to 66°N). Northern populations initiated growth and flowering earlier, flowered for a shorter period, were shorter, produced more and larger winter buds, and were older at first reproduction than southern populations. Flower morphology varied significantly among populations, but was, with the exception of calyx length, not significantly related to latitude of origin. Survival in the common garden (at 63°49′N) was positively correlated with latitude of origin and the size and number of winter buds produced in the preceding year. The results suggest that the among‐population differences in phenology and life history have evolved in response to latitudinal variation in length of the growing season. Further studies are required to determine whether population differentiation in flower morphology is maintained by selection.     

Developmental differences in visceral morphology of megophryine pelobatid tadpoles in relation to their body form and mode of life

Tadpoles face severe packing constraints on viscera within the pleuro-peritoneal cavity because of their extremely short torsos—a feature they share with adult anurans—and the concomitant need for relatively slender torsos for efficient locomotion. We examined the effects of differences in body form and habits on the size, shape and development of viscera in three kinds of sympatric, stream-associated pelobatid tadpoles. Leptobrachium montanumlarvae are generalized, wide, deep-bodied tadpoles. Larval Leptolalax gracilis are very slender and live in the crevices between rocks on the bottom of riffles. Larval Megophrys nasuta are intermediate between the other two in body form, and live with L. montanum in a variety of microhabitats but feed at the surface film. In all three species, liver, gall bladder, arid kidneys begin development early and grow isometrically throughout larval life. The gut and pancreas have a growth spurt shortly after hatching, then grow at a constant rate until near metamorphosis when both shrink drastically. The spleen grows at a slower rate than the body throughout the larval period. Lungs do not appear in L. gracilis until the tadpole approaches metamorphosis, which accords with its benthic habits, whereas they grow throughout the larval period in L. montanum and M. nasuta. In M. nasuta, however, the lungs are unusually wide anteriorly; this shifts buoyancy forward and facilitates the head-up feeding posture characteristic of that species. Gonads appear early in L. montanum and L. gracilis, but not until near metamorphosis in M. nasuta. We suggest that accelerated gonadal development in tadpoles characterizes species that metamorphose close to their size at first reproduction. Leptobrachium montanum, with the bulkiest body and most generalized habits, has relatively and absolutely the largest gut, liver (x of combined gut and liver volume = 24%, of total volume), and kidneys. Leptolalax gracilis, the most slender tadpole, has relatively the smallest combined gut and liver volume (x = 10% of total volume). Other premetamorphic differences among the species were observed in gut coiling, liver, pancreas and kidney shape and left/right asymmetry of urogenital organs. The major interspecific differences we observed in the size, shape, and developmental patterns of viscera in tadpoles are clearly related to interspecific differences in torso shape, microhabitat distribution and mode of feeding.