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1.
Nature ; 565(7739): 351-355, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30651613

RESUMO

Reconstructing the locomotion of extinct vertebrates offers insights into their palaeobiology and helps to conceptualize major transitions in vertebrate evolution1-4. However, estimating the locomotor behaviour of a fossil species remains a challenge because of the limited information preserved and the lack of a direct correspondence between form and function5,6. The evolution of advanced locomotion on land-that is, locomotion that is more erect, balanced and mechanically power-saving than is assumed of anamniote early tetrapods-has previously been linked to the terrestrialization and diversification of amniote lineages7. To our knowledge, no reconstructions of the locomotor characteristics of stem amniotes based on multiple quantitative methods have previously been attempted: previous methods have relied on anatomical features alone, ambiguous locomotor information preserved in ichnofossils or unspecific modelling of locomotor dynamics. Here we quantitatively examine plausible gaits of the stem amniote Orobates pabsti, a species that is known from a complete body fossil preserved in association with trackways8. We reconstruct likely gaits that match the footprints, and investigate whether Orobates exhibited locomotor characteristics that have previously been linked to the diversification of crown amniotes. Our integrative methodology uses constraints derived from biomechanically relevant metrics, which also apply to extant tetrapods. The framework uses in vivo assessment of locomotor mechanics in four extant species to guide an anatomically informed kinematic simulation of Orobates, as well as dynamic simulations and robotics to filter the parameter space for plausible gaits. The approach was validated using two extant species that have different morphologies, gaits and footprints. Our metrics indicate that Orobates exhibited more advanced locomotion than has previously been assumed for earlier tetrapods7,9, which suggests that advanced terrestrial locomotion preceded the diversification of crown amniotes. We provide an accompanying website for the exploration of the filters that constrain our simulations, which will allow revision of our approach using new data, assumptions or methods.


Assuntos
Fósseis , Locomoção , Filogenia , Vertebrados/fisiologia , Jacarés e Crocodilos/anatomia & histologia , Jacarés e Crocodilos/fisiologia , Animais , Tamanho Corporal , Feminino , Iguanas/anatomia & histologia , Iguanas/fisiologia , Urodelos/anatomia & histologia , Urodelos/fisiologia , Vertebrados/anatomia & histologia
2.
J Anat ; 233(5): 636-643, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30079494

RESUMO

Because the musculoskeletal anatomy of the trunk is the framework for the behaviors of locomotion, ventilation, and body support in lepidosaurs, comparative study of trunk anatomy in this group is critical for unraveling the selective pressures leading to extant diversity in axial form and function among vertebrates. This work uses gross dissection and computed tomography to describe the muscular and skeletal anatomy of the trunk of varanid lizards (Varanidae, Anguimorpha). Gross muscle dissections were conducted to investigate the axial muscular anatomy of Varanus exanthematicus, Varanus giganteus, Varanus rosenbergi, and Varanus panoptes. Computed tomography scans of these and additional varanid lizards from the Varanus and Odatria subgenera were conducted to investigate rib and vertebral number and gross morphology. The number of vertebrae differs between species, with 27-35 presacral and 47-137 postsacral vertebrae. Although the number of floating and abdominal ribs in varanids is variable, most species examined have three to four cervical ribs and three true ribs. Attachment and insertion points of the epaxial and hypaxial musculature are detailed. The body wall has four main hypaxial layers, from superficial to deep: oliquus externus, intercostalis externi, intercostalis internii, and transversus. Varanids differ from other investigated lepidosaurs in having supracostalis dorsus brevis (epaxial) and levator costae (hypaxial), which independently connect each rib to the vertebral column. Although more basic muscle descriptions of the body wall in reptiles are needed, comparisons with the condition in the green iguana (Iguana iguana) can be made.


Assuntos
Osso e Ossos/anatomia & histologia , Iguanas/anatomia & histologia , Músculo Esquelético/anatomia & histologia , Tronco/anatomia & histologia , Animais
3.
PLoS One ; 12(5): e0176434, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28459829

RESUMO

The extent to which evolution is deterministic (predictable), or random, is a fundamental question in evolution. This case study attempts to determine the extent to which interspecific divergence can be predicted from intraspecific trends related species. The mountainous Lesser Antilles are occupied by one or two anole species with very substantial intraspecific differences in the quantitative traits between xeric and rainforest habitats. These ecologically determined differences tend to be in parallel in each island species. A related species (Anolis bonairensis) lives on the far more xeric island of Bonaire, and this study tests the extent to which its interspecific divergence in hue and pattern traits can be predicted from the parallel intraspecific variation exhibited in Lesser Antillean anoles. Regression against a multivariate climate variable suggests that the hue and pattern of the Bonaire anole are consistently predicted from the ecologically determined intraspecific variation of its Lesser Antillean relatives. However, this predictability may be less consistent with other character systems, for example, scalation.


Assuntos
Evolução Biológica , Ambientes Extremos , Iguanas/genética , Animais , Clima , Iguanas/anatomia & histologia , Iguanas/fisiologia , Ilhas , Modelos Genéticos , Análise Multivariada , Filogenia , Análise de Regressão , Pigmentação da Pele/genética , Especificidade da Espécie
4.
Artigo em Inglês | MEDLINE | ID: mdl-28011410

RESUMO

Oxygen consumption (VO2), heart rate (fH), heart mass (Mh) and body mass (Mb) were measured during embryonic incubation and in hatchlings of green iguana (Iguana iguana). Mean fH and VO2 were unvarying in early stage embryos. VO2 increased exponentially during the later stages of embryonic development, doubling by the end of incubation, while fH was constant, resulting in a 2.7-fold increase in oxygen pulse. Compared to late stage embryos, the mean inactive level of VO2 in hatchlings was 1.7 fold higher, while fH was reduced by half resulting in a further 3.6 fold increase in oxygen pulse. There was an overall negative correlation between mean fH and VO2 when data from hatchlings was included. Thus, predicting metabolic rate as VO2 from measurements of fH is not possible in embryonic reptiles. Convective transport of oxygen to supply metabolism during embryonic incubation was more reliably indicated as an index of cardiac output (COi) derived from the product of fH and Mh. However, a thorough analysis of factors determining rates of oxygen supply during development and eclosion in reptiles will require cannulation of blood vessels that proved impossible in the present study, to determine oxygen carrying capacity by the blood and arteriovenous oxygen content difference (A-V diff), plus patterns of blood flow.


Assuntos
Iguanas/crescimento & desenvolvimento , Iguanas/fisiologia , Animais , Peso Corporal , Débito Cardíaco , Coração/anatomia & histologia , Frequência Cardíaca , Iguanas/anatomia & histologia , Tamanho do Órgão , Consumo de Oxigênio
5.
Zootaxa ; 4205(1): zootaxa.4205.1.4, 2016 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-27988595

RESUMO

We describe a new species of Stenocercus from the montane forest of the right margin of the Marañón river in the northern portion of the Central Andes in northern Peru (Amazonas and La Libertad departments), at elevations ranging from 2300 to 3035 m. Stenocercus omari sp. nov. differs from other Stenocercus species, with the exception of S. amydrorhytus, S. chrysopygus, S. cupreus, S. johaberfellneri, S. latebrosus, S. melanopygus, S. modestus, S. ornatissimus, S. orientalis, and S. stigmosus, by having granular scales on the posterior surfaces of thighs, a conspicuous antehumeral fold and by lacking a vertebral crest. However, Stenocercus omari sp. nov. is easily distinguished from the aforementioned species, except S. orientalis, by the presence of prominently keeled dorsal head scales. The new species differs from S. orientalis by lacking a prominent oblique neck fold and by having a distinct deep postfemoral mite pocket.


Assuntos
Iguanas/classificação , Animais , Feminino , Florestas , Iguanas/anatomia & histologia , Masculino , Peru , Rios
6.
Zootaxa ; 4138(2): 381-91, 2016 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-27470771

RESUMO

The Paris Natural History Museum herpetological collection (MNHN-RA) has seven historical specimens of Brachylophus spp. collected late in the 18th and early in the 19th centuries. Brachylophus fasciatus was described in 1800 by Brongniart but its type was subsequently considered as lost and never present in MNHN-RA collections. We found that 220 year old holotype among existing collections, registered without any data, and we show that it was donated to MNHN-RA from Brongniart's private collection after his death in 1847. It was registered in the catalogue of 1851 but without any data or reference to its type status. According to the coloration (uncommon midbody saddle-like dorsal banding pattern) and morphometric data given in its original description and in the subsequent examination of the type in 1802 by Daudin and in 1805 by Brongniart we found that lost holotype in the collections. Another MNHN-RA specimen has Horn Islands (Wallis and Futuna) as the collection location but we show that most of the collections given to MNHN-RA by its collector, Louis Arnoux, have mixed localities in the MNHN-RA catalogues. We thus conclude that the locality is wrong and that the species never inhabited those islands located west of Western Samoa and north-east of Fiji.


Assuntos
Iguanas/classificação , Distribuição Animal , Estruturas Animais/anatomia & histologia , Estruturas Animais/crescimento & desenvolvimento , Animais , Tamanho Corporal , Ecossistema , Feminino , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , Iguanas/anatomia & histologia , Iguanas/crescimento & desenvolvimento , Masculino , Museus/história , Tamanho do Órgão , Zoologia/história
7.
Zootaxa ; 3946(2): 201-20, 2015 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-25947685

RESUMO

A new species of the hitherto monotypic genus Chalarodon is described from southern Madagascar and a lectotype (ZMB 4360) is designated for C. madagascariensis Peters, 1854. The new species of terrestrial iguana, Chalarodon steinkampi sp. nov., is defined by several morphological characters and by concordant differentiation in mitochondrial and nuclear DNA with >5% uncorrected pairwise genetic distance in the 16S rRNA gene. It can be most clearly recognized by the presence of smooth (vs. keeled) gular and ventral scales, a spotted pattern extending from flanks onto belly, and an unpigmented throat. The new species is known from only a small area between the villages of Amboasary Sud and Esomony, located west of the Andohahela Massif, while C. madagascariensis appears to be widespread over much of southern and western Madagascar. We highlight the need for further exploration of this unprotected region which might host several other microendemic species.


Assuntos
Iguanas/anatomia & histologia , Iguanas/classificação , Animais , Feminino , Iguanas/genética , Madagáscar , Masculino , RNA Ribossômico 16S , Análise de Sequência de DNA , Especificidade da Espécie
8.
Pesqui. vet. bras ; 34(supl.1): 69-73, dez. 2014. ilus
Artigo em Português | LILACS, VETINDEX | ID: lil-778357

RESUMO

O crânio representa o segmento com conspícuas adaptações que, nos lagartos, podem ser conservativas ou impulsionadas por pressões seletivas. Objetivando subsidiar o conhecimento morfológico dos répteis, fornecemos uma descrição detalhada dos ossos que formam o neurocrânio de Iguana iguana iguana com base na análise de três esqueletos secos de espécimes adultos. O crânio da referia espécie possui características basais entre os lagartos sem o fechamento das aberturas cranianas e formato geral triangular. As estruturas ósseas que formam a base craniana apresentam muitas fusões, principalmente no assoalho. Na face caudal o exoccipital e o opistótico estão fundidos e formam o otoccipital, que contribui para a formação dos terços laterais do côndilo occipital. A parte central do côndilo é formada pelo supraoccipital. Fusões e estruturas esqueléticas presentes em Iguana são similares aos demais lagartos. Não foram descritas autapomorfias no neurocrânio para esta espécie.(AU)


Skull represents the segment with conspicuous adaptations that, in lizards, may be conservative or promoted by selective pressures. The aim of assisting the morphological knowledge of reptiles, we provide a detailed description of the neurocranium of Iguana iguana iguana based on analysis of three dried adult skeletons. The skull of this species has basal characteristics in lizards without closure of cranial openings and general triangular shape. Bony structures that form the caudal base have many fusions, especially on the floor. In the caudal face the exoccipital and the opisthotic are fused and form the otooccipital, which contributes to the formation of the lateral part of the condyle. The central part is formed by the condyle supraocciopital. Fusions and skeletal structures in Iguana are similar to other lizards. There are no autopomorphies in the neurocranium for this species.(AU)


Assuntos
Animais , Esqueleto/anatomia & histologia , Crânio/anatomia & histologia , Iguanas/anatomia & histologia
9.
Proc Natl Acad Sci U S A ; 111(48): 17218-23, 2014 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-25404314

RESUMO

The generally accepted framework for the evolution of a key feature of the avian respiratory system, unidirectional airflow, is that it is an adaptation for efficiency of gas exchange and expanded aerobic capacities, and therefore it has historically been viewed as important to the ability of birds to fly and to maintain an endothermic metabolism. This pattern of flow has been presumed to arise from specific features of the respiratory system, such as an enclosed intrapulmonary bronchus and parabronchi. Here we show unidirectional airflow in the green iguana, a lizard with a strikingly different natural history from that of birds and lacking these anatomical features. This discovery indicates a paradigm shift is needed. The selective drivers of the trait, its date of origin, and the fundamental aerodynamic mechanisms by which unidirectional flow arises must be reassessed to be congruent with the natural history of this lineage. Unidirectional flow may serve functions other than expanded aerobic capacity; it may have been present in the ancestral diapsid; and it can occur in structurally simple lungs.


Assuntos
Evolução Biológica , Iguanas/fisiologia , Pulmão/fisiologia , Fenômenos Fisiológicos Respiratórios , Vertebrados/fisiologia , Adaptação Fisiológica/fisiologia , Aerobiose , Jacarés e Crocodilos/anatomia & histologia , Jacarés e Crocodilos/fisiologia , Animais , Aves/anatomia & histologia , Aves/fisiologia , Iguanas/anatomia & histologia , Lagartos/anatomia & histologia , Lagartos/fisiologia , Pulmão/anatomia & histologia , Consumo de Oxigênio/fisiologia , Respiração , Especificidade da Espécie , Vertebrados/anatomia & histologia , Vertebrados/classificação
10.
J Vet Cardiol ; 16(3): 185-96, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-25127666

RESUMO

OBJECTIVES: To describe characteristics of echocardiography and cranial coelomic radiography in a cohort of iguanas. ANIMALS: Twenty apparently healthy adult green iguanas (Iguana iguana) from a reptile sanctuary. METHODS: Physical examination, radiography, two-dimensional and color Doppler echocardiography were performed to assess cardiac structures and function, and any related normal or abnormal findings were recorded. RESULTS: Echocardiographic examination was possible without sedation and allowed visualization of the great vessels, atria, and ventricle. Some structures could not be evaluated in a minority of the iguanas due to individual differences in bony conformation and imaging quality. Suspected abnormal echocardiographic findings in 3 iguanas included pericardial effusion (n = 1) and enlarged caudal vena cava and/or sinus venosus (n = 2). Objective measurements were repeatable as assessed by within-subject coefficient of variation, and reliable as assessed by intra-observer intraclass correlation coefficient. Left atrial and ventricular measurements were significantly correlated with body weight. Valve regurgitation was common, with atrioventricular valve regurgitation present in 53% (9/17) and aortic or pulmonic valve regurgitation in 71% (12/17) of otherwise normal iguanas. A heart murmur was not appreciated during examination of any of the iguanas. Heart size cannot be measured radiographically due to superimposition and silhouetting of other coelomic structures. Echocardiographic or radiographic findings consistent with mineralization of the great vessels were present in 76% of iguanas (13/17). CONCLUSIONS: Echocardiography in iguanas is well tolerated without sedation and allowed both subjective evaluation and structural measurements. Valve regurgitation and great vessel mineralization were commonly observed in this cohort of apparently healthy adult iguanas.


Assuntos
Coração/anatomia & histologia , Iguanas/anatomia & histologia , Animais , Estudos de Coortes , Ecocardiografia Doppler/veterinária , Ecocardiografia Doppler em Cores/veterinária , Feminino , Coração/fisiologia , Doenças das Valvas Cardíacas/diagnóstico por imagem , Doenças das Valvas Cardíacas/veterinária , Masculino , Radiografia Torácica/veterinária , Valores de Referência
11.
BMC Vet Res ; 10: 112, 2014 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-24885935

RESUMO

BACKGROUND: Contrast-enhanced diagnostic imaging techniques are considered useful in veterinary and human medicine to evaluate liver perfusion and focal hepatic lesions. Although hepatic diseases are a common occurrence in reptile medicine, there is no reference to the use of contrast-enhanced ultrasound (CEUS) and contrast-enhanced computed tomography (CECT) to evaluate the liver in lizards. Therefore, the aim of this study was to evaluate the pattern of change in echogenicity and attenuation of the liver in green iguanas (Iguana iguana) after administration of specific contrast media. RESULTS: An increase in liver echogenicity and density was evident during CEUS and CECT, respectively. In CEUS, the mean ± SD (median; range) peak enhancement was 19.9% ± 7.5 (18.3; 11.7-34.6). Time to peak enhancement was 134.0 ± 125.1 (68.4; 59.6-364.5) seconds. During CECT, first visualization of the contrast medium was at 3.6 ± 0.5 (4; 3-4) seconds in the aorta, 10.7 ± 2.2 (10.5; 7-14) seconds in the hepatic arteries, and 15 ± 4.5 (14.5; 10-24) seconds in the liver parenchyma. Time to peak was 14.1 ± 3.4 (13; 11-21) and 31 ± 9.6 (29; 23-45) seconds in the aorta and the liver parenchyma, respectively. CONCLUSION: CEUS and dynamic CECT are practical means to determine liver hemodynamics in green iguanas. Distribution of contrast medium in iguana differed from mammals. Specific reference ranges of hepatic perfusion for diagnostic evaluation of the liver in iguanas are necessary since the use of mammalian references may lead the clinician to formulate incorrect diagnostic suspicions.


Assuntos
Meios de Contraste/farmacologia , Iguanas/anatomia & histologia , Fígado/irrigação sanguínea , Fígado/fisiologia , Tomografia Computadorizada por Raios X/veterinária , Ultrassonografia/veterinária , Anestesia Geral/veterinária , Animais , Feminino , Masculino , Tomografia Computadorizada por Raios X/métodos , Ultrassonografia/métodos
12.
Zootaxa ; 3753: 47-58, 2014 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-24872278

RESUMO

We describe a new species of Stenocercus from the interandean valley of Río Chotano on the Amazonian slope of the northern portion of the Cordillera Occidental of Peru (Cajamarca Region), at elevations of between 1997 and 2318 m. Stenocercus arndti sp. nov. differs from other Stenocercus, except from S. bolivarensis, S. carrioni, S. chlorostictus, S. crassicaudatus, S. empetrus, S. eunetopsis, S. simonsii, and S. torquatus, in having granular scales on the posterior surface of the thighs, two caudal whorls per autotomic segment, mucronate caudal scales, and distinct longitudinal row of enlarged vertebral scales. However, Stenocercus arndti sp. nov. is easily distinguished from these species in having a bold black transversal band at midbody that extends ventrolaterally in adult males.


Assuntos
Iguanas/anatomia & histologia , Iguanas/classificação , Distribuição Animal , Animais , Feminino , Iguanas/fisiologia , Masculino , Peru
13.
Anat Rec (Hoboken) ; 297(3): 397-409, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24482428

RESUMO

Ecomorphological studies of lizards have explored the role of various morphological traits and how these may be associated with, among other things, habitat use. We present an analysis of selected traits of internal morphology of the hind limbs of Neotropical iguanian lizards and their relationship to habitat use. Considering that one of the most widely-held hypotheses relating to the origin of grasping is associated with the exploitation of the narrow-branch arboreal habitat, we include subdivisions of this designation as two of our ecologically defined categories of habitat exploitation for analysis, and compare lizards assigned to these categories to the features displayed by terrestrial lizards. The influence of phylogeny in shaping the morphology of lizards was assessed by using the comparative method. K values were significant for several osteological traits. Most of the K values for the variables based upon muscle and tendon morphometric characters (13 out 21), by contrast, had values <1, suggesting that their variation cannot be explained by phylogeny alone. Results of our phylogenetic and conventional ANCOVA analyses reveal that the characters highlighted through the application of the comparative method are not absolutely related to habitat in terms of the categories considered here. It appears that the bauplan of the lizard pes incorporates a morphological configuration that is sufficiently versatile to enable exploitation of almost all of the available habitats. As unexpected as conservation of internal gross morphology appears, it represents a means of accommodating to environmental challenges by apparently permitting adequacy for all situations examined.


Assuntos
Comportamento Animal , Hábitos , Membro Posterior/anatomia & histologia , Iguanas/anatomia & histologia , Atividade Motora , Adaptação Fisiológica , Análise de Variância , Animais , Evolução Biológica , Fenômenos Biomecânicos , Feminino , Membro Posterior/fisiologia , Iguanas/fisiologia , Masculino , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/fisiologia , Filogenia , Tendões/anatomia & histologia , Tendões/fisiologia
14.
Syst Biol ; 63(2): 119-33, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24262383

RESUMO

Current molecular methods of species delimitation are limited by the types of species delimitation models and scenarios that can be tested. Bayes factors allow for more flexibility in testing non-nested species delimitation models and hypotheses of individual assignment to alternative lineages. Here, we examined the efficacy of Bayes factors in delimiting species through simulations and empirical data from the Sceloporus scalaris species group. Marginal-likelihood scores of competing species delimitation models, from which Bayes factor values were compared, were estimated with four different methods: harmonic mean estimation (HME), smoothed harmonic mean estimation (sHME), path-sampling/thermodynamic integration (PS), and stepping-stone (SS) analysis. We also performed model selection using a posterior simulation-based analog of the Akaike information criterion through Markov chain Monte Carlo analysis (AICM). Bayes factor species delimitation results from the empirical data were then compared with results from the reversible-jump MCMC (rjMCMC) coalescent-based species delimitation method Bayesian Phylogenetics and Phylogeography (BP&P). Simulation results show that HME and sHME perform poorly compared with PS and SS marginal-likelihood estimators when identifying the true species delimitation model. Furthermore, Bayes factor delimitation (BFD) of species showed improved performance when species limits are tested by reassigning individuals between species, as opposed to either lumping or splitting lineages. In the empirical data, BFD through PS and SS analyses, as well as the rjMCMC method, each provide support for the recognition of all scalaris group taxa as independent evolutionary lineages. Bayes factor species delimitation and BP&P also support the recognition of three previously undescribed lineages. In both simulated and empirical data sets, harmonic and smoothed harmonic mean marginal-likelihood estimators provided much higher marginal-likelihood estimates than PS and SS estimators. The AICM displayed poor repeatability in both simulated and empirical data sets, and produced inconsistent model rankings across replicate runs with the empirical data. Our results suggest that species delimitation through the use of Bayes factors with marginal-likelihood estimates via PS or SS analyses provide a useful and complementary alternative to existing species delimitation methods.


Assuntos
Teorema de Bayes , Simulação por Computador , Iguanas/classificação , Filogenia , Animais , Iguanas/anatomia & histologia , Iguanas/genética , Cadeias de Markov , Método de Monte Carlo , Proteínas de Répteis/genética , Especificidade da Espécie
15.
Anat Histol Embryol ; 42(6): 453-60, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23410482

RESUMO

Contrast-enhanced computed tomographic studies of the coelomic cavity in four green iguanas, four black and white tegus and four bearded dragons were performed using a conventional CT scanner. Anatomical reference cross sections were obtained from four green iguana, four black and white tegu and six bearded dragon cadavers; the specimens were stored in a -20°C freezer for 24 h then sliced into 5-mm intervals. The frozen sections were cleaned with water and photographed on both sides. The individual anatomical structures were identified by means of the available literature; these were labelled first on the anatomical images and then matched to the corresponding computed tomography images. The results provide an atlas of the normal cross-sectional and computed tomographic anatomy of the coelomic cavity in the green iguana, the black and white tegu and the bearded dragon, which is useful in the interpretation of any imaging modality.


Assuntos
Anatomia Transversal , Iguanas/anatomia & histologia , Lagartos/anatomia & histologia , Tomografia Computadorizada por Raios X/veterinária , Tronco/anatomia & histologia , Animais , Feminino , Masculino
16.
J Morphol ; 274(3): 294-306, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23115131

RESUMO

The perivertebral musculature of lizards is critical for the stabilization and the mobilization of the trunk during locomotion. Some trunk muscles are also involved in ventilation. This dual function of trunk muscles in locomotion and ventilation leads to a biomechanical conflict in many lizards and constrains their ability to breathe while running ("axial constraint") which likely is reflected by their high anaerobic scope. Furthermore, different foraging and predator-escape strategies were shown to correlate with the metabolic profile of locomotor muscles in lizards. Because knowledge of muscle's fiber-type composition may help to reveal a muscle's functional properties, we investigated the distribution pattern of muscle fiber types in the perivertebral musculature in two small lizard species with a generalized body shape and subjected to the axial constraint (Dipsosaurus dorsalis, Acanthodactylus maculatus) and one species that circumvents the axial constraint by means of gular pumping (Varanus exanthematicus). Additionally, these species differ in their predator-escape and foraging behaviors. Using refined enzyme-histochemical protocols, muscle fiber types were differentiated in serial cross-sections through the trunk, maintaining the anatomical relationships between the skeleton and the musculature. The fiber composition in Dipsosaurus and Acanthodactylus showed a highly glycolytic profile, consistent with their intermittent locomotor style and reliance on anaerobic metabolism during activity. Because early representatives of diapsids resemble these two species in several postcranial characters, we suggest that this glycolytic profile represents the plesiomorphic condition for diapsids. In Varanus, we found a high proportion of oxidative fibers in all muscles, which is in accordance with its high aerobic scope and capability of sustained locomotion.


Assuntos
Lagartos/anatomia & histologia , Lagartos/fisiologia , Fibras Musculares Esqueléticas/citologia , Músculo Esquelético/anatomia & histologia , Animais , Evolução Biológica , Feminino , Iguanas/anatomia & histologia , Iguanas/fisiologia , Locomoção/fisiologia , Masculino , Fibras Musculares Esqueléticas/classificação , Músculo Esquelético/fisiologia , Tronco
17.
Zootaxa ; 3609: 291-301, 2013 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-24699591

RESUMO

We describe a new species of Stenocercus from an interandean valley of the upper Río Huallaga on the Amazonian slope of central Peru (Región Huánuco), at an elevation of 1700-1900 m. The new species differs from other Stenocercus, except S. boettgeri, S. haenschi, S. humeralis, and S. varius, by the combination of the following characters: presence of granular scales on the posterior surface of the thighs, enlarged vertebrals, three caudal whorls per autotomic segment, a medially complete antegular fold, non-spinose caudals, and by males lacking a black transverse band on the ventral surface of the neck. However, the new Stenocercus differs from these, with the exception of S. humeralis, by having more scales around the midbody (104-107, =105.66) than S. boettgeri (79-104, Mean= 88.61), S. haenschi (57-64, Mean=60.50), and S. varius (74-88, Mean=82.35); and from S. humeralis by having the scales in the frontonasal region nearly equal in size to the scales in the occipitoparietal region, while in S. humeralis the scales on the frontonasal region are twice or three times longer than the scales on the occipitoparietal region.


Assuntos
Iguanas/anatomia & histologia , Iguanas/classificação , Animais , Ecossistema , Feminino , Iguanas/fisiologia , Masculino , Peru , Árvores
19.
PLoS One ; 6(12): e28465, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22162772

RESUMO

The ratio between lengths of digit II and IV (digit ratio 2D:4D) is a morphological feature that likely affects tetrapod locomotor performances in different microhabitats. Modifications of this trait may be triggered by changes in steroids concentrations during embryo development, which might reflect direct selection acting on digit ratio or be solely a consequence of hormonal differences related for example to body size. Here we apply both conventional and phylogenetic analyses on morphological data from 25 lizard species of 3 families of Iguania (Iguanidae, Polychrotidae, and Tropiduridae), in order to verify whether selective pressures related to locomotion in different microhabitats could override the prenatal developmental cues imposed on the digit ratio 2D:4D by differences in body size between males and females. Data suggest that this trait evolved in association with ecological divergence in the species studied, despite the clear effect of body size on the digit ratio 2D:4D. The ecological associations of size-corrected digit ratios were restricted to one sex, and females of species that often use perches exhibited small digit ratios in the front limbs, which translated into larger sexual dimorphism indexes of arboreal species. The results, together with the subsequent discussion, provide outlines for further investigation about possible developmental mechanisms related to the evolution of adaptive changes in digit lengths that may have occurred during the evolution of ecological divergence in squamates.


Assuntos
Extremidades/fisiologia , Iguanas/fisiologia , Adaptação Fisiológica , Animais , Evolução Biológica , Tamanho Corporal , Ecologia , Extremidades/anatomia & histologia , Feminino , Iguanas/anatomia & histologia , Lagartos , Masculino , Modelos Estatísticos , Filogenia , Reprodutibilidade dos Testes , Caracteres Sexuais , Especificidade da Espécie
20.
Anat Rec (Hoboken) ; 294(1): 119-31, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21157923

RESUMO

Unlike extant birds and mammals, most non-avian theropods had large muscular tails, with muscle arrangements similar to those of modern reptiles. Examination of ornithomimid and tyrannosaurid tails revealed sequential diagonal scarring on the lateral faces of four or more hemal spines that consistently correlates with the zone of the tail just anterior to the disappearance of the vertebral transverse processes. This sequential scarring is interpreted as the tapering boundary between the insertions of the M. caudofemoralis and the M. ilioischiocaudalis. Digital muscle reconstructions based on measurements of fossil specimens and dissections of modern reptiles showed that the M. caudofemoralis of many non-avian theropods was exceptionally large. These high caudofemoral mass estimates are consistent with the elevation of the transverse processes of the caudal vertebra above the centrum, which creates an enlarged hypaxial region. Dorsally elevated transverse processes are characteristic of even primitive theropods and suggest that a large M. caudofemoralis is a basal characteristic of the group. In the genus Tyrannosaurus, the mass of the M. caudofemoralis was further increased by dorsoventrally lengthening the hemal arches. The expanded M. caudofemoralis of Tyrannosaurus may have evolved as compensation for the animal's immense size. Because the M. caudofemoralis is the primary hind limb retractor, large M. caudofemoralis masses and the resulting contractile force and torque estimates presented here indicate a sizable investment in locomotive muscle among theropods with a range of body sizes and give new evidence in favor of greater athleticism, in terms of overall cursoriality, balance, and turning agility.


Assuntos
Jacarés e Crocodilos/fisiologia , Tamanho Corporal/fisiologia , Dinossauros/fisiologia , Iguanas/fisiologia , Locomoção/fisiologia , Cauda/fisiologia , Jacarés e Crocodilos/anatomia & histologia , Animais , Evolução Biológica , Fenômenos Biomecânicos/fisiologia , Dinossauros/anatomia & histologia , Iguanas/anatomia & histologia , Movimento/fisiologia , Cauda/anatomia & histologia
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