Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.006
Filtrar
1.
Nature ; 613(7945): 614, 2023 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-36639443
2.
Proc Biol Sci ; 289(1987): 20221947, 2022 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-36382514

RESUMO

The late Quaternary is characterized by the extinction of many terrestrial megafauna, which included tortoises (Family: Testudinidae). However, limited information is available on how extinction shaped the phenotype of surviving taxa. Here, based on a global dataset of straight carapace length, we investigate the temporal variation, spatial distribution and evolution of tortoise body size over the past 23 million years, thereby capturing the effects of Quaternary extinctions in this clade. We found a significant change in body size distribution characterized by a reduction of both mean body size and maximum body size of extant tortoises relative to fossil taxa. This reduction of body size occurred earlier in mainland (Early Pleistocene 2.588-0.781 Ma) than in island tortoises (Late Pleistocene/Holocene 0.126-0 Ma). Despite contrasting body size patterns between fossil and extant taxa on a spatial scale, tortoise body size showed limited variation over time until this decline. Body size is a fundamental functional trait determining many aspects of species ecologies, with large tortoises playing key roles as ecosystem engineers. As such, the transition from larger sized to smaller sized classes indicated by our findings likely resulted in the homogenization of tortoises' ecological functions and diminished the role of tortoises in structuring the vegetation community.


Assuntos
Tartarugas , Animais , Tartarugas/anatomia & histologia , Ecossistema , Tamanho Corporal , Fósseis , Extinção Biológica
3.
Sci Rep ; 12(1): 18322, 2022 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-36396968

RESUMO

Marine turtles were common in the subtropical Upper Cretaceous epi-continental seas that once washed the coasts of the ancient European archipelago. But unlike its contemporaneous faunas from North America, in Europe no taxon surpassed the 1.5 m shell-length. Here, the remains of a new large marine turtle, Leviathanochelys aenigmatica gen. et sp. nov., from the Middle Campanian of the Southern Pyrenees are described. Anatomical and histological evidence concur in identifying the specimen as a basal chelonioid. The new taxon autapomorphically differs from other marine turtles by possessing an additional process on the anteromedial side of the pelvis, and an acetabulum directed strongly ventrally. Based on the pelvis size, it is likely that Leviathanochelys was as large as Archelon, thus becoming one of the largest marine turtles found to ever exist. The large body size of the new taxon could have evolved as a response to the unique habitat conditions of the European Cretaceous archipelago seas. The presence of the accessory pubic process further suggests the occurrence of an additional insertion point of the Musculus rectus abdominis, which together with the paleohistologic evidences support the hypothesis that the new taxon had an open marine pelagic lifestyle.


Assuntos
Tartarugas , Animais , Tartarugas/anatomia & histologia , Fósseis , Répteis , Europa (Continente) , América do Norte
4.
Nat Commun ; 13(1): 5807, 2022 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-36220806

RESUMO

The labyrinth of the vertebrate inner ear is a sensory system that governs the perception of head rotations. Central hypotheses predict that labyrinth shape and size are related to ecological adaptations, but this is under debate and has rarely been tested outside of mammals. We analyze the evolution of labyrinth morphology and its ecological drivers in living and fossil turtles, an understudied group that underwent multiple locomotory transitions during 230 million years of evolution. We show that turtles have unexpectedly large labyrinths that evolved during the origin of aquatic habits. Turtle labyrinths are relatively larger than those of mammals, and comparable to many birds, undermining the hypothesis that labyrinth size correlates directly with agility across vertebrates. We also find that labyrinth shape variation does not correlate with ecology in turtles, undermining the widespread expectation that reptilian labyrinth shapes convey behavioral signal, and demonstrating the importance of understudied groups, like turtles.


Assuntos
Orelha Interna , Tartarugas , Animais , Aves , Fósseis , Mamíferos , Filogenia , Tartarugas/anatomia & histologia
5.
Evolution ; 76(11): 2566-2586, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36117268

RESUMO

Turtles have a highly modified body plan, including a rigid shell that constrains postcranial anatomy. Skull morphology and neck mobility may therefore be key to ecological specialization in turtles. However, the ecological signal of turtle skull morphologies has not been rigorously evaluated, leaving uncertainties about the roles of ecological adaptation and convergence. We evaluate turtle cranial ecomorphology using three-dimensional geometric morphometrics and phylogenetic comparative methods. Skull shape correlates with allometry, neck retraction capability, and different aquatic feeding ecologies. We find that ecological variables influence skull shape only, whereas a key functional variable (the capacity for neck retraction) influences both shape and size. Ecology and functional predictions from three-dimensional shape are validated by high success rates for extant species, outperforming previous two-dimensional approaches. We use this to infer ecological and functional traits of extinct species. Neck retraction evolved among crownward stem-turtles by the Late Jurassic, signaling functional decoupling of the skull and neck from the shell, possibly linked to a major episode of ecomorphological diversification. We also find strong evidence for convergent ecological adaptations among marine groups. This includes parallel loss of neck retraction, evidence for active hunting, possible grazing, and suction feeding in extinct marine groups. Our large-scale assessment of dietary and functional adaptation throughout turtle evolution reveals the timing and origin of their distinct ecomorphologies, and highlights the potential for ecology and function to have distinct effects on skull form.


Tartarugas tem um plano corpóreo bastante modificado, que inclui um casco rígido que restringe sua anatomia pós-craniana. Portanto, a morfologia craniana e a mobilidade do pescoço devem ser centrais nas especializações ecológicas de tartarugas. No entanto, o sinal ecológico das diferentes morfologias de crânio de tartarugas não foi ainda rigorosamente avaliado, deixando incertezas sobre os papéis de adaptações ecológicas e convergência. Avaliamos a ecomorfologia craniana de tartarugas utilizando morfometria geométrica tridimensional e métodos filogenéticos comparativos. A forma craniana correlaciona com alometria, capacidade de retração do pescoço e diferentes ecologias alimentares aquáticas. Encontramos que variáveis ecológicas influenciam apenas a forma do crânio, enquanto uma importante variável funcional (a capacidade de retração do pescoço) influencia tanto a forma como o tamanho do crânio. Predições ecológicas e funcionais para espécies viventes a partir de formas tridimensionais são validadas com altas taxas de sucesso, superando abordagens bidimensionais. Utilizamos isso para inferir traços ecológicos e funcionais de espécies extintas. A retração do pescoço evoluiu em linhagens extintas mais próximas à origem do grupo-coronal durante o Jurássico Final, indicando uma dissociação funcional entre crânio e pescoço do casco, algo possivelmente ligado a um importante episódio de diversificação ecomorfológica. Também encontramos forte evidência para adaptações ecológicas convergentes em grupos marinhos. Isso inclui a perda paralela da retração do pescoço, evidência de caça ativa, alimentação por sucção, além de possível preferência por plantas aquáticas em grupos marinhos extintos. Nosso estudo de larga-escala sobre adaptações funcionais e relacionadas à dieta ao longo da evolução de tartarugas revela o tempo e origem de suas distintas ecomorfologias, e destaca ainda o potencial de ecologia e função terem efeitos distintos sobre a forma craniana.


Assuntos
Tartarugas , Animais , Tartarugas/anatomia & histologia , Filogenia , Crânio/anatomia & histologia , Pescoço/anatomia & histologia , Cabeça , Evolução Biológica
6.
J Vet Med Sci ; 84(7): 1001-1009, 2022 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-35650112

RESUMO

Sea turtles have well developed lacrimal glands for their electrolyte homeostasis. In turtles, stapedial artery and palatine artery send branches to supply orbital region, but supply artery for lacrimal glands was not identified. Micro-CT scans showed dorsoventrally large lacrimal glands of sea turtle are supplied by both stapedial artery and palatine artery. The circulatory pattern in cranial region was reconstructed based on the micro-CT scans, showing that sea turtle has basically similar pattern with the common snapping turtle: stapedial artery supplies orbital region and mandibular artery is ramified from stapedial artery. We also investigate the foramen stapedio-temporalis in turtles using osteological specimens. The foramen stapedio-temporalis, where the stapedial artery passes through, has different size among four families of turtles. We compared the sum of cross sections of left and right foramen stapedio-temporalis since homeostasis of one individual is maintained by a pair of lacrimal glands. The size difference may reflect primarily the share of stapedial artery against palatine artery in cranial circulation pattern and blood supply of orbital regions. Our observations confirmed a significantly larger cross-section in the foramen stapedio-temporalis of sea turtles than other freshwater/terrestrial turtles. Since the circulatory pattern is shared, the size difference of foramen stapedio-temporalis reflects the amount of arterial blood supply to lacrimal glands. Therefore, the size of the foramen stapedio-temporalis may indicate marine adaptation of turtles and are applicable to both fossil and osteological specimens.


Assuntos
Tartarugas , Animais , Artérias/anatomia & histologia , Eletrólitos , Homeostase , Crânio/anatomia & histologia , Tartarugas/anatomia & histologia
7.
J Zoo Wildl Med ; 53(2): 402-411, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35758582

RESUMO

The subcarapacial vessel is a popular site for venipuncture and intravenous medication administration in chelonians. Reports of adverse effects when using this site have increased, prompting evaluation of its safety. This study aimed to evaluate the anatomy of the subcarapacial vessel in 25 individual chelonians (2 box turtles, 3 red-eared sliders, and 20 red-footed tortoises) using computed tomography (CT). Individuals were sedated and administered contrast in the subcarapacial vessel. The vessel was visualized in 50% of the box turtles and red-footed tortoises, and 100% of the red-eared sliders. All species had contrast extravasation in the subarachnoid space, with red-footed tortoises having the largest percentage (70% compared to 50% and 33% of box turtles and red-eared sliders, respectively). Extravasation of contrast in the trachea or bronchi (70%) and lungs (80%) was seen in the red-footed tortoises only. Higher prevalence of contrast extravasation in the red-footed tortoises is likely because of anatomical differences, including a more cranially extending lung field and domed-shaped carapace compared to the other species. These findings highlight the risk associated with using the subcarapacial vessel for intravenous medication administration in certain species of chelonian.


Assuntos
Extravasamento de Materiais Terapêuticos e Diagnósticos , Tartarugas , Animais , Extravasamento de Materiais Terapêuticos e Diagnósticos/veterinária , Tartarugas/anatomia & histologia
8.
Anat Rec (Hoboken) ; 305(6): 1359-1393, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-34605614

RESUMO

We present new fossil records of the geoemydid turtle Bridgeremys pusilla from the Uinta Formation of Utah. Turtles are abundant throughout the unit, and known taxa are similar to those from the older strata in the Upper Green River Basin in Wyoming from the Bridger and Washakie Formations. B. pusilla is known from Bridgerian deposits but was not previously known from after the Turtle Bluff Member of the Bridger Formation. The taxon was coveal with two species of the geoemydid Echmatemys (E. callopyge and E. wyomingensis), a common genus of extinct pond turtles known primarily from lacustrine and fluvial deposits in western North America, including the Uinta Basin. In addition to previously documented morphological differences, our geometric morphometric analyses revealed significant differences in epiplastral morphology between B. pusilla and the two coeval Echmatemys species. Bridgeremys pusilla shared several morphological characters with Testudinidae. However, our anatomical network analysis suggests that the carapace of B. pusilla distributed stress forces in a manner more similar to emydids (basal and derived) than to derived testudinoids (Testudinidae and Emydidae), including Echmatemys species. This finding changes our understanding of the ecology of the species and sheds light onto how geoemydid turtles of the Uinta Formation may have partitioned the available ecospace. These new Uintan records extend the geographic range of B. pusilla into the Uinta Basin and stratigraphically through the top of the Uinta Formation, extending the temporal range of the taxon by more than 4 million years through the Uintan North American Land Mammal Age to the base of the Duchesne River Formation.


Assuntos
Tartarugas , Animais , Ecologia , Fósseis , Mamíferos/anatomia & histologia , Filogenia , Tartarugas/anatomia & histologia , Utah
9.
Pesqui. vet. bras ; 42: e06953, 2022. tab, ilus
Artigo em Inglês | LILACS, VETINDEX | ID: biblio-1356553

RESUMO

In order to determine the main anatomopathological findings of Testudines necropsied in the Distrito Federal, all necropsy records performed at the "Laboratório de Patologia Veterinária" of the "Universidade de Brasília" (LPV-UnB) on Testudines during the period from January 2008 to July 2020 were reviewed. The 72 cases reviewed were grouped and classified according to species, sex, origin, season of occurrence, and diagnosis. In 69.44% of the cases the species was informed in the necropsy protocols, which included Phrynops geoffroanus (38%), Trachemys dorbigni (36%), Chelonoidis carbonaria (14%), Chelonoidis denticulata (10%) and Podocnemis expansa (2%). In 30.55% of the cases this parameter was not informed and were classified only as Testudines. In 41.66% of the cases the sex was informed, being female 22.22%, male 19.44%, and 58.33% were not informed. Of these animals 79.16% were from environmental agencies and 20.84% from zoos and/or guardians. In 70.83% of the animals analyzed they were directly related to the autumn and winter seasons, with June being the most frequent month (29.17%). The conclusive diagnosis was possible in 68.05% of the cases. The category of disorders caused by injurious agents (48.97%) was the most prevalent, followed by inflammatory disorders (32.65%) and nutritional and metabolic disorders (28.57%). The main diagnoses were carapace and/or plastron fracture with 30.61%, hepatic steatosis (20.40%) and pneumonia (10.22%). Most cases of carapace or plastron fracture and hepatic steatosis occurred in animals from environmental agencies.(AU)


Com o objetivo de determinar os principais achados anatomopatológicos de Testudines necropsiados no Distrito Federal, foram revisadas todas as fichas de necropsia realizadas no Laboratório de Patologia Veterinária da Universidade de Brasília (LPV-UnB) em Testudines, durante o período de janeiro de 2008 a julho de 2020. Os 72 casos revisados foram agrupados e classificados quanto à espécie, sexo, procedência, estação do ano de ocorrência e diagnóstico. Em 69,44% dos casos havia a espécie informada nos protocolos de necropsia, que incluíam Phrynops geoffroanus (38%), Trachemys dorbigni (36%), Chelonoidis carbonaria (14%), Chelonoidis denticulata (10%) e Podocnemis expansa (2%). Em 30,55% dos casos não tiveram esse parâmetro informado e foram classificados apenas como Testudines. Em 41,66% casos foi informado o sexo, sendo fêmea 22,22%, macho 19,44% e não informados 58,33%. Destes animais 79,16% eram de órgão ambiental e 20,84% de zoológicos e ou tutores. Em 70,83% dos animais analisados tiveram direta relação com as estações de outono e inverno, sendo o mês de junho o mais frequente (29,17%). O diagnóstico conclusivo foi possível em 68,05% dos casos. A categoria de distúrbios causados por agentes lesivos (48,97%) foi a mais prevalente, seguido por distúrbios inflamatórios (32,65%) e dos distúrbios nutricionais e metabólicos (28,57%). Os principais diagnósticos foram fratura de carapaça e ou plastrão com 30,61%, esteatose hepática (20,40%) e pneumonia (10,22%). A maior parte dos casos de fratura de carapaça ou plastrão e de esteatose hepática ocorreram em animais provenientes de órgão ambiental.(AU)


Assuntos
Animais , Pneumonia/mortalidade , Tartarugas/anatomia & histologia , Tartarugas/lesões , Fraturas Ósseas/mortalidade , Fígado Gorduroso/mortalidade , Autopsia/veterinária
10.
Curr Biol ; 31(16): R989-R990, 2021 08 23.
Artigo em Inglês | MEDLINE | ID: mdl-34428417

RESUMO

Tortoises (land turtles) are familiar animals and are generally assumed to be strict herbivores. Their ecological roles are most obvious in giant tortoise species which, due to their size and local abundance, play major roles as keystone species and ecosystem engineers1-3. In the Galápagos and Seychelles islands these species are known to play major roles as the islands' largest herbivores, with exceptionally high biomass and consuming up to 11% of primary production1. In addition they act as ecosystem engineers, dispersing seeds, breaking vegetation and eroding rocks2. However, as slow-moving poikilotherms most people assume their behaviour to be simple. Here we present video evidence of a Seychelles giant tortoise (Aldabrachelys gigantea) attacking a tern chick and pursuing it along a log. Finally the tortoise killed the chick and was observed to eat it. Other tortoises in the same area have been seen making similar attacks, although those were not fully documented. We believe that the exceptional combination of a tree-nesting tern colony with a resident giant tortoise population has created conditions leading to systematic hunting of birds by several individual tortoises; an entirely novel behavioural strategy for any tortoise species. VIDEO ABSTRACT.


Assuntos
Comportamento Predatório , Tartarugas , Animais , Aves , Ecossistema , Tartarugas/anatomia & histologia
11.
PLoS One ; 16(6): e0252355, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34081728

RESUMO

Late Jurassic deposits across Europe have yielded a rich fauna of extinct turtles. Although many of these turtles are recovered from marine deposits, it is unclear which of these taxa are habitually marine and which may be riverine species washed into nearby basins, as adaptations to open marine conditions are yet to be found. Two new fossils from the Late Jurassic of Germany provide unusually strong evidence for open marine adaptations. The first specimen is a partial shell and articulated hind limb from the Late Jurassic (early Tithonian) platy limestones of Schernfeld near Eichstätt, which preserves the integument of the hind limb as an imprint. The skin is fully covered by flat, polygonal scales, which stiffen the pes into a paddle. Although taxonomic attribution is not possible, similarities are apparent with Thalassemys. The second specimen is a large, articulated skeleton with hypertrophied limbs referable to Thalassemys bruntrutana from the Late Jurassic (early Late Kimmeridgian) platy limestone of Wattendorf, near Bamberg. Even though the skin is preserved as a phosphatic film, the scales are not preserved. This specimen can nevertheless be inferred to have had paddles stiffened by scales based on the pose in which they are preserved, the presence of epibionts between the digits, and by full morphological correspondence to the specimen from Schernfeld. An analysis of scalation in extant turtles demonstrated that elongate flippers stiffed by scales are a marine adaptation, in contrast to the elongate but flexible flippers of riverine turtles. Phylogenetic analysis suggests that Thalassemys bruntrutana is referable to the mostly Late Jurassic turtle clade Thalassochelydia. The marine adapted flippers of this taxon therefore evolved convergently with those of later clades of marine turtles. Although thalassochelydian fossils are restricted to Europe, with one notable exception from Argentina, their open marine adaptations combined with the interconnectivity of Jurassic oceans predict that the clade must have been even more wide-spread during that time.


Assuntos
Extremidades/anatomia & histologia , Fósseis/anatomia & histologia , Tartarugas/anatomia & histologia , Adaptação Fisiológica/fisiologia , Nadadeiras de Animais/anatomia & histologia , Animais , Fenômenos Biomecânicos/fisiologia , Carbonato de Cálcio/análise , Alemanha , Sistema Musculoesquelético/anatomia & histologia , Filogenia
12.
Sci Rep ; 11(1): 10396, 2021 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-34001926

RESUMO

Despite the relevance of chemical communication in vertebrates, comparative examinations of macroevolutionary trends in chemical signaling systems are scarce. Many turtle and tortoise species are reliant on chemical signals to communicate in aquatic and terrestrial macrohabitats, and many of these species possess specialized integumentary organs, termed mental glands (MGs), involved in the production of chemosignals. We inferred the evolutionary history of MGs and tested the impact of macrohabitat on their evolution. Inference of ancestral states along a time-calibrated phylogeny revealed a single origin in the ancestor of the subclade Testudinoidea. Thus, MGs represent homologous structures in all descending lineages. We also inferred multiple independent losses of MGs in both terrestrial and aquatic clades. Although MGs first appeared in an aquatic turtle (the testudinoid ancestor), macrohabitat seems to have had little effect on MG presence or absence in descendants. Instead, we find clade-specific evolutionary trends, with some clades showing increased gland size and morphological complexity, whereas others exhibiting reduction or MG loss. In sister clades inhabiting similar ecological niches, contrasting patterns (loss vs. maintenance) may occur. We conclude that the multiple losses of MGs in turtle clades have not been influenced by macrohabitat and that other factors have affected MG evolution.


Assuntos
Evolução Biológica , Tegumento Comum/fisiologia , Feromônios/química , Tartarugas/fisiologia , Comunicação Animal , Animais , Fenômenos Biomecânicos , Ecossistema , Tegumento Comum/anatomia & histologia , Feromônios/biossíntese , Filogenia , Transdução de Sinais/genética , Tartarugas/anatomia & histologia
13.
Sci Rep ; 11(1): 9555, 2021 05 20.
Artigo em Inglês | MEDLINE | ID: mdl-34017016

RESUMO

Four turtle taxa are previously documented from the Cenomanian Arlington Archosaur Site (AAS) of the Lewisville Formation (Woodbine Group) in Texas. Herein, we describe a new side-necked turtle (Pleurodira), Pleurochayah appalachius gen. et sp. nov., which is a basal member of the Bothremydidae. Pleurochayah appalachius gen. et sp. nov. shares synapomorphic characters with other bothremydids, including shared traits with Kurmademydini and Cearachelyini, but has a unique combination of skull and shell traits. The new taxon is significant because it is the oldest crown pleurodiran turtle from North America and Laurasia, predating bothremynines Algorachelus peregrinus and Paiutemys tibert from Europe and North America respectively. This discovery also documents the oldest evidence of dispersal of crown Pleurodira from Gondwana to Laurasia. Pleurochayah appalachius gen. et sp. nov. is compared to previously described fossil pleurodires, placed in a modified phylogenetic analysis of pelomedusoid turtles, and discussed in the context of pleurodiran distribution in the mid-Cretaceous. Its unique combination of characters demonstrates marine adaptation and dispersal capability among basal bothremydids.


Assuntos
Fósseis , Tartarugas , Distribuição Animal , Animais , Evolução Biológica , Fósseis/anatomia & histologia , Filogenia , Texas , Tartarugas/anatomia & histologia , Tartarugas/classificação , Tartarugas/genética
14.
Vet Clin North Am Exot Anim Pract ; 24(2): 341-367, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33892891

RESUMO

"Respiratory tract disease in chelonians can be difficult to treat and as such proper diagnostics are paramount. Infectious agents that can affect the respiratory tract of chelonians include viral, bacterial, fungal, and parasitic organisms. Noninfectious diseases can also develop. Because chelonians lack a proper diaphragm, changes in size of celomic organs can cause compression of the respiratory system. These conditions result in clinical signs that could be attributed to the respiratory system, such as open-mouth breathing. In this article, anatomy, physiology, and current standards for diagnostics and treatments of major diseases of the respiratory tract in chelonians are discussed."


Assuntos
Sistema Respiratório/anatomia & histologia , Doenças Respiratórias/veterinária , Tartarugas/anatomia & histologia , Animais , Sistema Respiratório/patologia , Doenças Respiratórias/diagnóstico , Doenças Respiratórias/microbiologia , Doenças Respiratórias/parasitologia
15.
PLoS One ; 16(4): e0250873, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33914838

RESUMO

We analyzed the internal structure of the nasal cavities of hawksbill, olive ridley and black sea turtles from computed tomography images. The nasal cavities of all three species consisted of a vestibule, nasopharyngeal duct and cavum nasi proprium that included anterodorsal, posterodorsal and anteroventral diverticula, and a small posteroventral salience formed by a fossa of the wall. These findings were similar to those of green and loggerhead sea turtles (Cheloniidae), but differed from those of leatherback sea turtles (Dermochelyidae). Compared to the Cheloniidae species, the nasal cavity in leatherback sea turtles was relatively shorter, wider and larger in volume. Those structural features of the nasal cavity of leatherback sea turtles might help to suppress heat dissipation and reduce water pressure within the nasal cavity in cold and deep waters.


Assuntos
Cavidade Nasal/anatomia & histologia , Cavidade Nasal/diagnóstico por imagem , Tartarugas/classificação , Animais , Feminino , Masculino , Especificidade da Espécie , Tomografia Computadorizada por Raios X , Tartarugas/anatomia & histologia
16.
Proc Biol Sci ; 288(1946): 20210213, 2021 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-33653130

RESUMO

Testudines are susceptible to inversion and self-righting using their necks, limbs or both, to generate enough mechanical force to flip over. We investigated how shell morphology, neck length and self-righting biomechanics scale with body mass during ontogeny in Chelydra serpentina, which uses neck-powered self-righting. We found that younger turtles flipped over twice as fast as older individuals. A simple geometric model predicted the relationships of shell shape and self-righting time with body mass. Conversely, neck force, power output and kinetic energy increase with body mass at rates greater than predicted. These findings were correlated with relatively longer necks in younger turtles than would be predicted by geometric similarity. Therefore, younger turtles self-right with lower biomechanical costs than predicted by simple scaling theory. Considering younger turtles are more prone to inverting and their shells offer less protection, faster and less costly self-righting would be advantageous in overcoming the detriments of inversion.


Assuntos
Tartarugas , Animais , Fenômenos Biomecânicos , Extremidades , Tartarugas/anatomia & histologia
17.
J Morphol ; 282(4): 543-552, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33491791

RESUMO

Turtles are characterized by their typical carapace, which is primarily composed of corneous beta proteins in the horny part and collagen in the dermal part. The formation of the extracellular matrix in the dermis of the carapace in a hard-shelled and a soft-shelled turtle has been compared. The study examines carapace development, with an emphasis on collagen accumulation, in the soft-shelled turtle Pelodiscus sinensis and hard-shelled turtle Trachemys scripta elegans, using comparative morphological and embryological analyses. The histological results showed that collagen deposition in the turtle carapace increased as the embryos developed. However, significant differences were observed between the two turtle species at the developmental stages examined. The microstructure of the dermis of the carapace of P. sinensis showed light and dark banding of collagen bundles, with a higher overall collagen content, whereas the carapacial matrix of T. scripta was characterized by loosely packed and thinner collagenous fiber bundles with a lower percentage of type I collagen. Overall, the formation and distribution of collagen fibrils at specific developmental stages are different between the soft-and hard-shelled turtles. These results indicate that the pliable epidermis of the soft-shelled turtle is supported by a strong dermis that is regularly distributed with collagen and that it allows improved maneuvering, whereas a strong but inflexible epidermis as observed in case of hard-shelled turtles limits movement.


Assuntos
Exoesqueleto/embriologia , Exoesqueleto/metabolismo , Colágeno/metabolismo , Derme/metabolismo , Tartarugas/embriologia , Exoesqueleto/citologia , Animais , Colágeno/genética , Epiderme , Regulação da Expressão Gênica , Tartarugas/anatomia & histologia
18.
J Zoo Wildl Med ; 51(4): 879-888, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33480568

RESUMO

Ophthalmic studies of the Texas tortoise (Gopherus berlandieri) established normal ophthalmic parameters for select diagnostic tests in captive tortoises and assessment of differences among individuals of differing size and health status. Sixty-one tortoises of varying weight, shell size, Mycoplasma seroprevalence, and herpesvirus exposure were included. Complete ophthalmic examinations, including neuro-ophthalmic reflexes, phenol red thread test, rebound tonometry, fluorescein staining, palpebral fissure length measurement, slit lamp biomicroscopy, indirect fundoscopy, and ocular ultrasound measurements of axial globe length, anterior chamber depth, lens thickness, and vitreous length, were recorded. All tortoises had negative dazzle and pupillary light reflexes, inconsistent menace responses, and positive palpebral reflexes. Mean ± SD tear production and intraocular pressure (IOP) were 14.2 ± 5.6 mm/15 sec and 13.8 ± 2.4 mm Hg in healthy tortoises, respectively. Mycoplasma-seropositive tortoises (with or without herpesvirus exposure) had significantly increased tear production (20.2 ± 8.1 and 19.9 ± 8.9 mm/15 sec, respectively) compared with healthy seronegative tortoises (14.2 ± 5.6 mm/15 sec; P = 0.02). As body size decreased, so too did palpebral fissure length and ocular ultrasound measurements, while IOP increased. Overall, palpebral fissure length appeared relatively small, and tear production relatively increased compared with other chelonian species, likely on the basis of the relatively arid native habitat. Further work is recommended to establish baseline values in related species, as well as comparison in aquatic versus terrestrial chelonians. The authors further suggest that the finding of relatively increased tear production in tortoises may indicate the need to rule out mycoplasmosis as a cause of upper respiratory tract disease.


Assuntos
Olho/anatomia & histologia , Tartarugas/anatomia & histologia , Animais , Oftalmopatias/patologia , Feminino , Masculino , Mycoplasma/isolamento & purificação , Lágrimas , Tonometria Ocular
19.
Anat Rec (Hoboken) ; 304(3): 584-590, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-32478454

RESUMO

The morphology of the tetrapod nasal cavity has adapted to the environment in terms of olfaction and respiration. Reports indicate that the internal structure of the nasal cavity of green sea turtles is more complex than that of turtles in general, but whether or not it is similar among sea turtle species remains unknown. The present study aimed to define the internal structures of the nasal cavity of green (Chelonian mydas), loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles using computed tomography. The nasal cavity of green and loggerhead sea turtles contained anterodorsal, anteroventral, posterodorsal diverticula and a posteroventral excavation in the middle. In contrast, the nasal cavity of leatherback sea turtles had more complicated dorsal region comprising anterodorsal and posterodorsal diverticula, and two excavations between the nostril and anterodorsal diverticulum, but no distinct structures at the ventral region. The airway in the nasal cavity was shorter and thicker in the leatherback, than in the green and loggerhead turtles. These species differences might reflect ecological variety and different evolutionary strategies.


Assuntos
Cavidade Nasal/anatomia & histologia , Tartarugas/anatomia & histologia , Animais , Feminino , Cavidade Nasal/diagnóstico por imagem , Especificidade da Espécie , Tomografia Computadorizada por Raios X
20.
J Morphol ; 282(2): 173-184, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33111991

RESUMO

Variations in the number and arrangement of scutes often are used for species identification in hard-shelled sea turtles. Despite the conserved nature of scute arrangements, anomalous arrangements have been noted in the literature for over a century, with anomalies linked to sub-optimal environmental conditions in the nest during development. Long-held assumptions suggest that anomalous scute arrangements are indicative of underlying physiological or morphological anomalies, with presumed long-term survival costs to the individual. Here, we examined a 25-year photo database of two species of sea turtle (Caretta caretta and Chelonia mydas) captured incidentally and non-selectively on the eastern coast of Florida. Our results suggest that C. mydas is substantially more variable with respect to the arrangement of carapacial scutes, while C. caretta had a relatively higher proportion of individuals with anomalous plastron scute arrangements. We also show evidence that (a) the forms and patterns of anomalous scutes are stable throughout growth; (b) there is limited evidence for selection against non-modal arrangements in the size classes that were examined; and (c) that their frequency has remained stable in juvenile cohorts from 1994 until present. These findings indicate that there may not be a survival cost associated with anomalous scute arrangements once the turtles reach juvenile size classes, and that variation in scute arrangements within populations is relatively common.


Assuntos
Exoesqueleto/anatomia & histologia , Tartarugas/anatomia & histologia , Animais , Bases de Dados como Assunto , Florida , Tamanho do Órgão
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...