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2.
BMC Evol Biol ; 20(1): 62, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32487135

RESUMO

BACKGROUND: The Chengjiang biota is one of the most species-rich Cambrian Konservat-Lagerstätten, and preserves a community dominated by non-biomineralized euarthropods. However, several Chengjiang euarthropods have an unfamiliar morphology, are extremely rare, or incompletely preserved. RESULTS: We employed micro-computed tomography to restudy the enigmatic euarthropod Jianshania furcatus. We reveal new morphological details, and demonstrate that the specimens assigned to this species represent two different taxa. The holotype of J. furcatus features a head shield with paired anterolateral notches, stalked lateral eyes, and an articulated tailspine with a bifurcate termination. The other specimen is formally redescribed as Xiaocaris luoi gen. et sp. nov., and is characterized by stalked eyes connected to an anterior sclerite, a subtrapezoidal head shield covering three small segments with reduced tergites, a trunk with 15 overlapping tergites with a well-developed dorsal keel, and paired tail flukes. CONCLUSIONS: The presence of antennae, biramous appendages with endopods composed of 15 articles, and multiple appendage pairs associated with the trunk tergites identify X. luoi nov. as a representative of Fuxianhuiida, an early branching group of stem-group euarthropods endemic to the early Cambrian of Southwest China. X. luoi nov. represents the fifth fuxianhuiid species described from the Chengjiang biota, and its functional morphology illuminates the ecological diversity of this important clade for understanding the early evolutionary history of euarthropods.


Assuntos
Artrópodes/anatomia & histologia , Biota , Microtomografia por Raio-X , Animais , Artrópodes/classificação , Evolução Biológica , Extremidades/anatomia & histologia , Fósseis , Cabeça/anatomia & histologia
3.
Nature ; 579(7800): 549-554, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32214248

RESUMO

The evolution of fishes to tetrapods (four-limbed vertebrates) was one of the most important transformations in vertebrate evolution. Hypotheses of tetrapod origins rely heavily on the anatomy of a few tetrapod-like fish fossils from the Middle and Late Devonian period (393-359 million years ago)1. These taxa-known as elpistostegalians-include Panderichthys2, Elpistostege3,4 and Tiktaalik1,5, none of which has yet revealed the complete skeletal anatomy of the pectoral fin. Here we report a 1.57-metre-long articulated specimen of Elpistostege watsoni from the Upper Devonian period of Canada, which represents-to our knowledge-the most complete elpistostegalian yet found. High-energy computed tomography reveals that the skeleton of the pectoral fin has four proximodistal rows of radials (two of which include branched carpals) as well as two distal rows that are organized as digits and putative digits. Despite this skeletal pattern (which represents the most tetrapod-like arrangement of bones found in a pectoral fin to date), the fin retains lepidotrichia (fin rays) distal to the radials. We suggest that the vertebrate hand arose primarily from a skeletal pattern buried within the fairly typical aquatic pectoral fin of elpistostegalians. Elpistostege is potentially the sister taxon of all other tetrapods, and its appendages further blur the line between fish and land vertebrates.


Assuntos
Evolução Biológica , Osso e Ossos/anatomia & histologia , Extremidades/anatomia & histologia , Fósseis , Vertebrados/anatomia & histologia , Nadadeiras de Animais/anatomia & histologia , Animais , Teorema de Bayes , Canadá , Peixes/anatomia & histologia , Filogenia
4.
Arthropod Struct Dev ; 55: 100916, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32179420

RESUMO

Megasecoptera is a late Paleozoic order of herbivorous insects with rostrum-like mouthparts and slender homonomous outstretched wings. Our knowledge of their morphology is mainly based on wings while other body parts are scarcely documented. Here we focus on the families Bardohymenidae and Aspidothoracidae. A new well preserved specimen of Sylvohymen cf. sibiricus is described and illustrated, particularly the structures of the external male genitalia previously unknown for Bardohymenidae. Sylvohymen marginatussp. nov. is described from the early Permian of Tshekarda based on unique traits in the wing venation. The genera Paleohymen and Taigahymen are both removed from Bardohymenidae and the latter is transferred to Vorkutiidae. Alexahymen aestatis (Brauckmann, 1991) comb. nov. from Pennsylvanian at Piesberg is transferred from Aspidothoracidae to Bardohymenidae. Piesbergbrodiagen. nov. is designated for Piesbergbrodia tristrata (Brauckmann and Herd, 2003) comb. nov. as a member of Brodiidae and the first known record of this family from Piesberg quarry. The placement of Sylvohymen peckae in the Bardohymenidae is considered doubtful due to lack of significant characters in its venation. Furthermore, our study is focused on the form of the apical cell and the pattern of wing pigmentation. Peculiarities of the integumental outgrowths and external genitalia of representatives of Aspidothoracidae and Bardohymenidae, and other close relatives, are highlighted.


Assuntos
Fósseis/anatomia & histologia , Insetos/anatomia & histologia , Asas de Animais/anatomia & histologia , Animais , Extremidades/anatomia & histologia , Genitália Masculina/anatomia & histologia , Insetos/classificação , Masculino
5.
Proc Natl Acad Sci U S A ; 117(3): 1612-1620, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31888998

RESUMO

The fin-to-limb transition was marked by the origin of digits and the loss of dermal fin rays. Paleontological research into this transformation has focused on the evolution of the endoskeleton, with little attention paid to fin ray structure and function. To address this knowledge gap, we study the dermal rays of the pectoral fins of 3 key tetrapodomorph taxa-Sauripterus taylori (Rhizodontida), Eusthenopteron foordi (Tristichopteridae), and Tiktaalik roseae (Elpistostegalia)-using computed tomography. These data show several trends in the lineage leading to digited forms, including the consolidation of fin rays (e.g., reduced segmentation and branching), reduction of the fin web, and unexpectedly, the evolution of asymmetry between dorsal and ventral hemitrichia. In Eusthenopteron, dorsal rays cover the preaxial endoskeleton slightly more than ventral rays. In Tiktaalik, dorsal rays fully cover the third and fourth mesomeres, while ventral rays are restricted distal to these elements, suggesting the presence of ventralized musculature at the fin tip analogous to a fleshy "palm." Asymmetry is also observed in cross-sectional areas of dorsal and ventral rays. Eusthenopteron dorsal rays are slightly larger than ventral rays; by contrast, Tiktaalik dorsal rays can be several times larger than ventral rays, and degree of asymmetry appears to be greater at larger sizes. Analysis of extant osteichthyans suggests that cross-sectional asymmetry in the dermal rays of paired fins is plesiomorphic to crown group osteichthyans. The evolution of dermal rays in crownward stem tetrapods reflects adaptation for a fin-supported elevated posture and resistance to substrate-based loading prior to the origin of digits.


Assuntos
Nadadeiras de Animais/anatomia & histologia , Extremidades/anatomia & histologia , Peixes/anatomia & histologia , Anfíbios , Nadadeiras de Animais/fisiologia , Animais , Evolução Biológica , Extremidades/fisiologia , Peixes/fisiologia , Fósseis , Paleontologia , Tomografia Computadorizada por Raios X
6.
Nat Commun ; 11(1): 224, 2020 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-31932633

RESUMO

Helicoidal formations often appear in natural microstructures such as bones and arthropods exoskeletons. Named Bouligands after their discoverer, these structures are angle-ply laminates that assemble from laminae of chitin or collagen fibers embedded in a proteinaceous matrix. High resolution electron microscope images of cross-sections through scorpion claws are presented here, uncovering structural features that are different than so-far assumed. These include in-plane twisting of laminae around their corners rather than through their centers, and a second orthogonal rotation angle which gradually tilts the laminae out-of-plane. The resulting Bouligand laminate unit (BLU) is highly warped, such that neighboring BLUs are intricately intertwined, tightly nested and mechanically interlocked. Using classical laminate analysis extended to laminae tilting, it is shown that tilting significantly enhances the laminate flexural stiffness and strength, and may improve toughness by diverting crack propagation. These observations may be extended to diverse biological species and potentially applied to synthetic structures.


Assuntos
Exoesqueleto/ultraestrutura , Escorpiões/ultraestrutura , Exoesqueleto/anatomia & histologia , Exoesqueleto/fisiologia , Animais , Anisotropia , Quitina/ultraestrutura , Elasticidade , Extremidades/anatomia & histologia , Dureza , Microscopia Eletrônica , Modelos Biológicos , Modelos Estruturais , Proteínas/ultraestrutura , Escorpiões/anatomia & histologia
7.
Schweiz Arch Tierheilkd ; 162(1): 53-60, 2020 Jan.
Artigo em Alemão | MEDLINE | ID: mdl-31899450

RESUMO

INTRODUCTION: The biography of Colonel Hermann Schwyter, equine surgeon of the Swiss Army from 1928 to 1937, and the history of training of farriers in Switzerland since the 18th century are presented. Hermann Schwyters dissertation examined the changes of equine hoof confirmation as a result of standing and gait in approximately 2,000 horses and numerous anatomical specimens. He defines the foot placement, describes possible variations, their causes and effects. Significant is also his study of the compression pathology in horses and mules. His recommendations are still valid today. The present article refers to his authored textbook "The Swiss military farrier" and to his established journal, which is bearing the same title.


Assuntos
Medicina Veterinária/história , Serviço Veterinário Militar/história , Dissertações Acadêmicas como Assunto/história , Animais , Livros/história , Livros Ilustrados/história , Extremidades/anatomia & histologia , História do Século XVIII , História do Século XIX , História do Século XX , Casco e Garras/anatomia & histologia , Cavalos , Publicações Periódicas como Assunto/história , Sapatos/história , Suíça
8.
Sci Data ; 7(1): 20, 2020 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-31941894

RESUMO

The skin, fat, and muscle of the musculoskeletal system provide essential support and protection to the human body. The interaction between individual layers and their composite structure dictate the body's response during mechanical loading of extremity surfaces. Quantifying such interactions may improve surgical outcomes by enhancing surgical simulations with lifelike tissue characteristics. Recently, a comprehensive tissue thickness and anthropometric database of in vivo extremities was acquired using a load sensing instrumented ultrasound to enhance the fidelity of advancing surgical simulations. However detailed anatomy of tissue layers of musculoskeletal extremities was not captured. This study aims to supplement that database with an enhanced dataset of in vitro specimens that includes ultrasound imaging supported by motion tracking of the ultrasound probe and two additional full field imaging modalities (magnetic resonance and computed tomography). The additional imaging datasets can be used in conjunction with the ultrasound/force data for more comprehensive modeling of soft tissue mechanics. Researchers can also use the image modalities in isolation if anatomy of legs and arms is needed.


Assuntos
Antropometria , Sistema Musculoesquelético/anatomia & histologia , Sistema Musculoesquelético/diagnóstico por imagem , Fenômenos Biomecânicos , Simulação por Computador , Extremidades/anatomia & histologia , Extremidades/diagnóstico por imagem , Humanos , Imagem por Ressonância Magnética , Procedimentos Cirúrgicos Operatórios , Tomografia Computadorizada por Raios X , Ultrassonografia
9.
BMC Evol Biol ; 20(1): 4, 2020 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-31914921

RESUMO

BACKGROUND: Early Cambrian Lagerstätten from China have greatly enriched our perspective on the early evolution of animals, particularly arthropods. However, recent studies have shown that many of these early fossil arthropods were more derived than previously thought, casting uncertainty on the ancestral euarthropod body plan. In addition, evidence from fossilized neural tissues conflicts with external morphology, in particular regarding the homology of the frontalmost appendage. RESULTS: Here we redescribe the multisegmented megacheirans Fortiforceps and Jianfengia and describe Sklerolibyon maomima gen. et sp. nov., which we place in Jianfengiidae, fam. nov. (in Megacheira, emended). We find that jianfengiids show high morphological diversity among megacheirans, both in trunk ornamentation and head anatomy, which encompasses from 2 to 4 post-frontal appendage pairs. These taxa are also characterized by elongate podomeres likely forming seven-segmented endopods, which were misinterpreted in their original descriptions. Plesiomorphic traits also clarify their connection with more ancestral taxa. The structure and position of the "great appendages" relative to likely sensory antero-medial protrusions, as well as the presence of optic peduncles and sclerites, point to an overall homology with the anterior head of radiodontans. This is confirmed by our Bayesian phylogeny, which places jianfengiids as the basalmost euarthropods, paraphyletic with other megacheirans, and in contiguity with isoxyids and radiodontans. CONCLUSIONS: Sklerolibyon and other jianfengiids expand the disparity of megacheirans and suggest that the common euarthropod ancestor possessed a remarkable phenotypic variability associated with the externalized cephalon, as well as endopods that were already heptopodomerous, which differs from previous hypotheses and observations. These animals also demonstrate that the frontalmost pair of arthrodized appendage is homologous between radiodontans and megacheirans, refuting the claim that the radiodontan frontal appendages evolved into the euarthropod labrum, and questioning its protocerebral identity. This evidence based on external anatomy now constitutes a solid benchmark upon which we should address issues of homology, with the help of carefully examined palaeoneurological data.


Assuntos
Artrópodes/anatomia & histologia , Fósseis , Animais , Artrópodes/classificação , Teorema de Bayes , Evolução Biológica , China , Extremidades/anatomia & histologia , Olho/anatomia & histologia , Cabeça/anatomia & histologia , Filogenia
10.
Syst Biol ; 69(2): 345-362, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-31596473

RESUMO

There is a growing body of research on the evolution of anatomy in a wide variety of organisms. Discoveries in this field could be greatly accelerated by computational methods and resources that enable these findings to be compared across different studies and different organisms and linked with the genes responsible for anatomical modifications. Homology is a key concept in comparative anatomy; two important types are historical homology (the similarity of organisms due to common ancestry) and serial homology (the similarity of repeated structures within an organism). We explored how to most effectively represent historical and serial homology across anatomical structures to facilitate computational reasoning. We assembled a collection of homology assertions from the literature with a set of taxon phenotypes for the skeletal elements of vertebrate fins and limbs from the Phenoscape Knowledgebase. Using seven competency questions, we evaluated the reasoning ramifications of two logical models: the Reciprocal Existential Axioms (REA) homology model and the Ancestral Value Axioms (AVA) homology model. The AVA model returned all user-expected results in addition to the search term and any of its subclasses. The AVA model also returns any superclass of the query term in which a homology relationship has been asserted. The REA model returned the user-expected results for five out of seven queries. We identify some challenges of implementing complete homology queries due to limitations of OWL reasoning. This work lays the foundation for homology reasoning to be incorporated into other ontology-based tools, such as those that enable synthetic supermatrix construction and candidate gene discovery. [Homology; ontology; anatomy; morphology; evolution; knowledgebase; phenoscape.].


Assuntos
Classificação/métodos , Modelos Biológicos , Nadadeiras de Animais/anatomia & histologia , Animais , Extremidades/anatomia & histologia , Vertebrados/anatomia & histologia
11.
Sci Adv ; 5(11): eaax5833, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31799393

RESUMO

Snakes represent one of the most dramatic examples of the evolutionary versatility of the vertebrate body plan, including body elongation, limb loss, and skull kinesis. However, understanding the earliest steps toward the acquisition of these remarkable adaptations is hampered by the very limited fossil record of early snakes. Here, we shed light on the acquisition of the snake body plan using micro-computed tomography scans of the first three-dimensionally preserved skulls of the legged snake Najash and a new phylogenetic hypothesis. These findings elucidate the initial sequence of bone loss that gave origin to the modern snake skull. Morphological and molecular analyses including the new cranial data provide robust support for an extensive basal radiation of early snakes with hindlimbs and pelves, demonstrating that this intermediate morphology was not merely a transient phase between limbed and limbless body plans.


Assuntos
Fósseis/anatomia & histologia , Crânio/anatomia & histologia , Serpentes/anatomia & histologia , Animais , Evolução Biológica , Extremidades/anatomia & histologia , Microtomografia por Raio-X
12.
Nature ; 575(7783): 489-493, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31695194

RESUMO

Many ideas have been proposed to explain the origin of bipedalism in hominins and suspension in great apes (hominids); however, fossil evidence has been lacking. It has been suggested that bipedalism in hominins evolved from an ancestor that was a palmigrade quadruped (which would have moved similarly to living monkeys), or from a more suspensory quadruped (most similar to extant chimpanzees)1. Here we describe the fossil ape Danuvius guggenmosi (from the Allgäu region of Bavaria) for which complete limb bones are preserved, which provides evidence of a newly identified form of positional behaviour-extended limb clambering. The 11.62-million-year-old Danuvius is a great ape that is dentally most similar to Dryopithecus and other European late Miocene apes. With a broad thorax, long lumbar spine and extended hips and knees, as in bipeds, and elongated and fully extended forelimbs, as in all apes (hominoids), Danuvius combines the adaptations of bipeds and suspensory apes, and provides a model for the common ancestor of great apes and humans.


Assuntos
Fósseis , Hominidae/classificação , Hominidae/fisiologia , Locomoção , Filogenia , Posição Ortostática , Animais , Extremidades/anatomia & histologia , Feminino , Hominidae/anatomia & histologia , Humanos , Masculino , Tíbia/anatomia & histologia , Ulna/anatomia & histologia
13.
Elife ; 82019 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-31612860

RESUMO

Drosophila melanogaster males perform a series of courtship behaviors that, when successful, result in copulation with a female. For over a century, mutations in the yellow gene, named for its effects on pigmentation, have been known to reduce male mating success. Prior work has suggested that yellow influences mating behavior through effects on wing extension, song, and/or courtship vigor. Here, we rule out these explanations, as well as effects on the nervous system more generally, and find instead that the effects of yellow on male mating success are mediated by its effects on pigmentation of male-specific leg structures called sex combs. Loss of yellow expression in these modified bristles reduces their melanization, which changes their structure and causes difficulty grasping females prior to copulation. These data illustrate why the mechanical properties of anatomy, not just neural circuitry, must be considered to fully understand the development and evolution of behavior.


Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Preferência de Acasalamento Animal/fisiologia , Pigmentação/genética , Animais , Evolução Biológica , Fenômenos Biomecânicos , Copulação/fisiologia , Corte , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila/deficiência , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/anatomia & histologia , Drosophila melanogaster/metabolismo , Extremidades/anatomia & histologia , Feminino , Regulação da Expressão Gênica , Masculino , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
14.
PLoS One ; 14(10): e0223851, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31600318

RESUMO

In the pig, intrauterine competition (IUC) greatly affects postnatal traits, such as birth weight, but also locomotor capacities. In a previous study, our group discovered a lower motor performance in piglets with a low birth weight and low vitality (L piglets), compared to piglets with a normal birth weight and normal vitality (N piglets). In order to explain the force deficit causing this reduced motor performance, in a subsequent study, we investigated whether this deficit in L piglets was caused by a lower force generating capacity (FGC) of the extensors of the hind limb and/or a lower number of type II (fast-twitch) fibers in m. vastus lateralis. L piglets had a lower absolute FGC, but surprisingly, a higher relative FGC (to birth weight) in the hind limb, compared to N piglets. In addition, we found no differences in fiber composition of m. vastus lateralis. In the present study, we assessed whether this higher relative FGC is a common feature for front and hind limb locomotor muscles of L piglets. To that end, the physiological cross-sectional area of the main extensor muscles of the front limb was calculated from their volume and fiber length, in order to calculate both the absolute and the relative FGC. By immunohistochemical staining of m. triceps brachii caput longum, the percentage of type II (fast-contracting) fibers could be determined. Similar to the results of the hind limb, we found a smaller absolute FGC, but a larger relative FGC in the front limb of L piglets, compared to N piglets. In addition, m. triceps brachii caput longum did not have a different muscle fiber composition in L and N piglets. As such, we can conclude that IUC affects the locomotor muscles in the front and hind limb in a similar way and that the observed force deficit in L piglets cannot be explained by a different force generating capacity or a lower percentage of type II muscle fibers.


Assuntos
Extremidades/embriologia , Tamanho da Ninhada de Vivíparos , Movimento , Músculo Esquelético/fisiologia , Organogênese , Animais , Animais Recém-Nascidos/anatomia & histologia , Fenômenos Biomecânicos , Peso ao Nascer , Extremidades/anatomia & histologia , Extremidades/fisiologia , Feminino , Masculino , Contração Muscular , Músculo Esquelético/embriologia , Gravidez , Suínos
15.
Commun Biol ; 2: 329, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31508504

RESUMO

Traditionally, the origin and evolution of modern arthropod body plans has been revealed through increasing levels of appendage specialisation exhibited by Cambrian euarthropods. Here we show significant variation in limb morphologies and patterns of limb-tagmosis among three early Cambrian arthropod species conventionally assigned to the Bradoriida. These arthropods are recovered as a monophyletic stem-euarthropod group (and sister taxon to crown-group euarthropods, i.e. Chelicerata, Mandibulata and their extinct relatives), thus implying a radiation of stem-euarthropods where trends towards increasing appendage specialisation were explored convergently with other euarthropod groups. The alternative solution, where bradoriids are polyphyletic, representing several independent origins of a small, bivalved body plan in lineages from diverse regions of the euarthropod and mandibulate stems, is only marginally less parsimonious. The new data reveal a previously unknown disparity of body plans in stem-euarthropods and both solutions support remarkable evolutionary convergence, either of fundamental body plans or appendage specialization patterns.


Assuntos
Artrópodes/anatomia & histologia , Animais , Extremidades/anatomia & histologia , Extremidades/diagnóstico por imagem , Filogenia , Microtomografia por Raio-X
16.
PLoS One ; 14(9): e0221824, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31518353

RESUMO

The Palorchestidae are a family of marsupial megafauna occurring across the eastern Australian continent from the late Oligocene through to their extinction in the Late Pleistocene. The group is known for their odd 'tapir-like' crania and distinctive clawed forelimbs, but their appendicular anatomy has never been formally described. We provide the first descriptions of the appendicular skeleton and body mass estimates for three palorchestid species, presenting newly-identified, and in some cases associated, material of mid-Miocene Propalorchestes, Plio-Pleistocene Palorchestes parvus and Pleistocene Palorchestes azael alongside detailed comparisons with extant and fossil vombatiform marsupials. We propose postcranial diagnostic characters at the family, genus and species level. Specialisation in the palorchestid appendicular skeleton evidently occurred much later than in the cranium and instead correlates with increasing body size within the lineage. We conclude that palorchestid forelimbs were highly specialised for the manipulation of their environment in the acquisition of browse, and that they may have adopted bipedal postures to feed. Our results indicate palorchestids were bigger than previously thought, with the largest species likely weighing over 1000 kg. Additionally, we show that P. azael exhibits some of the most unusual forelimb morphology of any mammal, with a uniquely fixed humeroulnar joint unlike any of their marsupial kin, living or extinct.


Assuntos
Marsupiais/anatomia & histologia , Animais , Austrália , Tamanho Corporal , Osso e Ossos/anatomia & histologia , Extinção Biológica , Extremidades/anatomia & histologia , Fósseis/anatomia & histologia , Marsupiais/classificação , Marsupiais/fisiologia , Crânio/anatomia & histologia , Especificidade da Espécie
17.
J Morphol ; 280(10): 1582-1599, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31429975

RESUMO

Among geckos, the acquisition of the adhesive system is associated with several morphological changes of the feet that are involved in the operation of the adhesive apparatus. However, analyses using a comparative framework are lacking. We applied traditional morphometrics and geometric morphometric analysis with phylogenetic comparative methods to morphological data, collected from X-ray scans, to examine patterns of morphological evolution of the pes in association with the gain and loss of adhesive capabilities, and with habitat occupancy among 102 species of gecko. Padbearing gecko lineages tend to have shorter digits and greater inter-digital angles than padless ones. Arboreal and saxicolous species have shorter digits than terrestrial species. Our results suggest repeated shifts that converge upon a similar padbearing morphology, with some modifications being associated with the habitat occupied. We demonstrate that functional innovation and habitat can operate on, and influence, different components of foot morphology.


Assuntos
Evolução Biológica , Extremidades/anatomia & histologia , Lagartos/anatomia & histologia , Animais , Ecossistema , Lagartos/classificação , Lagartos/genética , Filogenia
18.
BMC Evol Biol ; 19(1): 165, 2019 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-31387545

RESUMO

BACKGROUND: Artiopodan euarthropods represent common and abundant faunal components in sites with exceptional preservation during the Cambrian. The Chengjiang biota in South China contains numerous taxa that are exclusively known from this deposit, and thus offer a unique perspective on euarthropod diversity during the early Cambrian. One such endemic taxon is the non-trilobite artiopodan Sinoburius lunaris, which has been known for approximately three decades, but few details of its anatomy are well understood due to its rarity within the Chengjiang, as well as technical limitations for the study of these fossils. Furthermore, the available material does not provide clear information on the ventral organization of this animal, obscuring our understanding of phylogenetically significant details such as the appendages. RESULTS: We employed X-ray computed tomography to study the non-biomineralized morphology of Sinoburius lunaris. Due to the replacement of the delicate anatomy with pyrite typical of Chengjiang fossils, computed tomography reveals substantial details of the ventral anatomy of Sinoburius lunaris, and allow us to observe in detail the three-dimensionally preserved appendicular organization of this taxon for the first time. The dorsal exoskeleton consists of a crescent-shaped head shield with well-developed genal spines, a thorax with seven freely articulating tergites, and a fused pygidium with lateral and median spines. The head bears a pair of ventral stalked eyes that are accommodated by dorsal exoskeletal bulges, and an oval elongate ventral hypostome. The appendicular organization of the head is unique among Artiopoda. The deutocerebral antennae are reduced, consisting of only five podomeres, and bear an antennal scale on the second podomere that most likely represents an exite rather than a true ramus. The head includes four post-antennal biramous limb pairs. The first two biramous appendages are differentiated from the rest. The first appendage pair consists of a greatly reduced endopod coupled with a greatly elongated exopod with a potentially sensorial function. The second appendage pair carries a more conventionally sized endopod, but also has an enlarged exopod. The remaining biramous appendages are homonomous in their construction, but decrease in size towards the posterior end of the body. They consist of a basipodite with ridge-like crescentic endites, an endopod with seven podomeres and a terminal claw, and a lamellae-bearing exopod with a slender shaft. Contrary to previous reports, we confirm the presence of segmental mismatch in Sinoburius lunaris, expressed as diplotergites in the thorax. Maximum parsimony and Bayesian phylogenetic analyses support the monophyly of Xandarellida within Artiopoda, and illuminate the internal relationships within this enigmatic clade. Our results allow us to propose a transformation series explaining the origin of archetypical xandarellid characters, such as the evolution of eye slits in Xandarella spectaculum and Phytophilaspis pergamena as derivates from the anterolateral notches in the head shield observed in Cindarella eucalla and Luohuilinella species. In this context, Sinoburius lunaris is found to feature several derived characters within the group, such as the secondary loss of eye slits and a high degree of appendicular tagmosis. Contrary to previous findings, our analyses strongly support close affinities between Sinoburius lunaris, Xandarella spectaculum and Phytophilaspis pergamena, although the precise relationships between these taxa are sensitive to different methodologies. CONCLUSIONS: The revised morphology of Sinoburius lunaris, made possible through the use of computed tomography to resolve details of its three-dimensionally preserved appendicular anatomy, contributes towards an improved understanding of the morphology of this taxon and the evolution of Xandarellida more broadly. Our results indicate that Sinoburius lunaris possesses an unprecedented degree of appendicular tagmosis otherwise unknown within Artiopoda, with the implication that this iconic group of Palaeozoic euarthropods likely had a more complex ecology and functional morphology than previously considered. The application of computer tomographic techniques to the study of Chengjiang euarthropods holds exceptional promise for understanding the morphological diversity of these organisms, and also better reconstructing their phylogenetic relationships and evolutionary history.


Assuntos
Artrópodes/anatomia & histologia , Artrópodes/classificação , Evolução Biológica , Fósseis , Animais , Artrópodes/genética , Teorema de Bayes , Biota , China , Extremidades/anatomia & histologia , Cabeça/anatomia & histologia , Filogenia , Tórax/anatomia & histologia
19.
Integr Comp Biol ; 59(5): 1382-1398, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31397852

RESUMO

Grasshoppers, Melanoplus sanguinipes (Orthoptera: Acrididae), develop larger head width (HW) and shorter leg length, relative to body size, when fed low nutrient, lignin-rich grasses compared to sibs fed a diet of high nutrient grasses. To elucidate how underlying genetic variation and plasticity of growth generate plasticity of this linear static allometry within coarse-grained environments, I measured head and leg size of three nymphal instars and adult grasshoppers raised on either a low or high nutrient diet within a half-sib quantitative genetic experiment. Doubly-multivariate repeated measures multiple analysis of variance (MANOVA) of head, mandible, and hind leg size and their rate of growth (mm/period) and growth period (days) through ontogeny were used to analyze how the ontogeny of diet-induced plasticity for these variables and additive genetic variation for plasticity (genotype × environment interaction [G×E]) contribute to plasticity in functional linear static allometry. Genetic variation for diet-induced plasticity (G×E) of head and leg size varied through ontogeny, as did genetic variation for plasticity of growth in third and fourth instar nymphs. Despite extensive genetic variation in plasticity of HW and leg length in fourth instar nymphs, the static allometry between head and leg was stable within each diet because the patterns of G×E were similar for HW, leg length and their coordinated growth. Nutrient sensitive plasticity in growth shifted the intercept but not the slope of static allometry, a result consistent with one outcome of a graphical model of the relationships between G× E and plasticity of within environment static allometry. In addition, G×E of fourth instar head and leg size was reduced in adults by negatively size-dependent, convergent growth in the last period of ontogeny. Consequently, the bivariate reaction norms of head and leg size for adults exhibited no G×E and, again, plasticity in the intercept but not in the slope of static allometry. The ontogeny of seemingly simple diet-induced linear static allometry between functional body parts in grasshoppers arises from a complex combination of differing patterns of nutrient-sensitive growth, duration of growth, convergent growth, and G×E, all relevant to understanding the development and evolution of functional allometry in hemimetabolous insects.


Assuntos
Adaptação Fisiológica , Dieta , Interação Gene-Ambiente , Gafanhotos/crescimento & desenvolvimento , Animais , Tamanho Corporal , Extremidades/anatomia & histologia , Extremidades/crescimento & desenvolvimento , Feminino , Gafanhotos/anatomia & histologia , Gafanhotos/genética , Cabeça/anatomia & histologia , Cabeça/crescimento & desenvolvimento , Masculino , Ninfa/anatomia & histologia , Ninfa/genética , Ninfa/crescimento & desenvolvimento
20.
Naturwissenschaften ; 106(7-8): 38, 2019 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-31209559

RESUMO

Xiphosurida-crown group horseshoe crabs-are a group of morphologically conservative marine chelicerates (at least since the Jurassic). They represent an idealised example of evolutionary stasis. Unfortunately, body fossils of horseshoe crabs seldom preserve appendages and their associated features; thus, an important aspect of their morphology is absent in explorations of their conservative Bauplan. As such, fossil horseshoe crab appendages are rarely considered within a comparative framework: previous comparisons have focussed almost exclusively on extant taxa to the exclusion of extinct taxa. Here, we examine eight specimens of the xiphosurid Tachypleus syriacus (Woodward, 1879) from the Cenomanian (ca 100 Ma) Konservat-Lagerstätten of Lebanon, five of which preserve the cephalothoracic and thoracetronic appendages in exceptional detail. Comparing these appendages of T. syriacus with other fossil xiphosurids highlights the conserved nature of appendage construction across Xiphosurida, including examples of Austrolimulidae, Paleolimulidae, and Limulidae. Conversely, Belinuridae have more elongate cephalothoracic appendages relative to body length. Differences in appendage sizes are likely related to the freshwater and possible subaerial life modes of belinurids, contrasting with the primarily marine habits of other families. The morphological similarity of T. syriacus to extant members of the genus indicates that the conserved nature of the generic lineage can be extended to ecological adaptations, notably burrowing, swimming, possible diet, and sexual dimorphism.


Assuntos
Evolução Biológica , Fósseis/anatomia & histologia , Caranguejos Ferradura/anatomia & histologia , Caranguejos Ferradura/classificação , Adaptação Fisiológica , Animais , Ecossistema , Extremidades/anatomia & histologia , Filogenia , Especificidade da Espécie
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