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1.
Proc Natl Acad Sci U S A ; 117(6): 3034-3044, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31988131

RESUMO

Developmental novelties often underlie the evolutionary origins of key metazoan features. The anuran urostyle, which evolved nearly 200 MYA, is one such structure. It forms as the tail regresses during metamorphosis, when locomotion changes from an axial-driven mode in larvae to a limb-driven one in adult frogs. The urostyle comprises of a coccyx and a hypochord. The coccyx forms by fusion of caudal vertebrae and has evolved repeatedly across vertebrates. However, the contribution of an ossifying hypochord to the coccyx in anurans is unique among vertebrates and remains a developmental enigma. Here, we focus on the developmental changes that lead to the anuran urostyle, with an emphasis on understanding the ossifying hypochord. We find that the coccyx and hypochord have two different developmental histories: First, the development of the coccyx initiates before metamorphic climax whereas the ossifying hypochord undergoes rapid ossification and hypertrophy; second, thyroid hormone directly affects hypochord formation and appears to have a secondary effect on the coccygeal portion of the urostyle. The embryonic hypochord is known to play a significant role in the positioning of the dorsal aorta (DA), but the reason for hypochordal ossification remains obscure. Our results suggest that the ossifying hypochord plays a role in remodeling the DA in the newly forming adult body by partially occluding the DA in the tail. We propose that the ossifying hypochord-induced loss of the tail during metamorphosis has enabled the evolution of the unique anuran bauplan.


Assuntos
Anuros , Evolução Biológica , Cóccix , Metamorfose Biológica/fisiologia , Animais , Anuros/anatomia & histologia , Anuros/embriologia , Anuros/crescimento & desenvolvimento , Cóccix/anatomia & histologia , Cóccix/embriologia , Cóccix/crescimento & desenvolvimento , Larva/anatomia & histologia , Larva/crescimento & desenvolvimento , Notocorda/anatomia & histologia , Notocorda/embriologia , Notocorda/crescimento & desenvolvimento
2.
Integr Zool ; 15(1): 40-54, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31149773

RESUMO

It is well known that environmental temperature influences several biological functions of ectotherms, notably in amphibians. The high permeability of anuran skin, associated with the effect of elevated environmental temperature, potentiates the dehydration process and this combination may restrict locomotor performance. Thoropa taophora is an endemic species from the Atlantic Rainforest whose tadpoles are semiterrestrial and predominantly diurnal, and are found in rocky seashores where they are exposed to sea spray and high temperatures. In this study we investigated how temperature and salinity conditions affect the locomotor performance in Thoropa taophora tadpoles. We also assessed how different osmotic concentrations affect the activity of the metabolic pathways that support muscle function. We measured the sprint speed of tadpoles of various sizes at different temperatures and salinities in the field. We also measured the activity of the enzymes pyruvate kinase (PK), lactate dehydrogenase (LDH) and citrate synthase (CS) in different temperatures and osmotic concentrations, and calculated the thermal sensitivity and the activity constants for each osmolality. Our results showed that, in general, sprint speed decreased with increasing temperature and salinity. However, whereas the effect of increased salinity was similar in smaller and larger tadpoles, increased temperature had a higher negative impact on sprint speed of larger tadpoles, thus indicating low thermal sensitivity of small tadpoles. PK and LDH thermal sensitivities and LDH constant of activity decreased as the osmolality increased. In conclusion, the locomotor capacity of tadpoles was decreased by temperature and salinity, which may be related to a decrease in anaerobic metabolism both in terms of sensitivity and total energy turnover through enzymatic activity. We discuss the ecological consequences, including the potential impacts on predator escape behavior promoted by changes in metabolism and locomotor performance in an early stage of development of this species.


Assuntos
Anuros/fisiologia , Temperatura Alta , Atividade Motora/efeitos dos fármacos , Salinidade , Cloreto de Sódio/farmacologia , Animais , Anuros/crescimento & desenvolvimento , Relação Dose-Resposta a Droga , Larva/efeitos dos fármacos , Larva/fisiologia , Atividade Motora/fisiologia , Cloreto de Sódio/administração & dosagem , Estresse Fisiológico
3.
An Acad Bras Cienc ; 91(4): e20190154, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31800706

RESUMO

Skeletochronology is the most accurate method to estimate a population age structure. The methodology is based on the analysis of secondary bone tissue in order to count growth rings. This study aimed to provide initial data, allowing researchers to further work out in the age of individuals and populations, sampling evidence of the presence of growth rings in 11 native species (representing nine families) of a subtropical region of southern Brazil. Four bone samples of each specimen were used to perform the skeletochronological analysis: the penultimate phalanges of the 3rd and 4th fingers, the humerus, and the femur. The presence of growth rings was confirmed in the periosteal layer of the bones of all analyzed species. In comparison with phalanges, growth rings of humeri and femora are more irregular and less distinguishable. This is the first record of growth rings to the native species herein analised. The skeletochronology was proved to be an effective tool in determining the age of anuran amphibians from a subtropical region, since this environment presents well defined climatic seasonality.


Assuntos
Determinação da Idade pelo Esqueleto/métodos , Anuros/anatomia & histologia , Anuros/crescimento & desenvolvimento , Animais , Brasil
4.
Ecotoxicol Environ Saf ; 186: 109794, 2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31629188

RESUMO

Glyphosate-based herbicides (GBHs) are widely-used agricultural chemicals, bringing potential detriments to aquatic organisms. Currently, our understanding of sublethal effects and underlying toxicologic mechanisms of GBHs are still limited, especially in amphibians. Here, the sublethal effects of a commercial GBH (KISSUN®) on tadpoles of a farmland dwelling frog, Microhyla fissipes, were investigated. The 10-d LC50 of "KISSUN®" GBH was 77.5 mg/L. Tadpoles exposed to 60-120 mg/L showed increased preference to higher temperature. After 10 days exposure, obvious growth suppression was observed in survived GBH-stressed tadpoles, characterized by dosage depended decrement in body mass, body width, total length, etc. GBH-stressed tadpoles also showed decreased tail length/snout-vent length ratio and smaller tail muscle fiber diameter. Comparative transcriptomics (control, 60 mg/L and 90 mg/L groups) was conducted to analyze the underlying molecular processes. GBH-stressed tadpoles showed downregulated transcription of ribosomal proteins and cytoskeleton proteins, which could explain their suppressed whole body and tail muscle growth. Moreover, GBH-stressed tadpoles showed transcriptional downregulation of carbohydrate and lipid catabolism, but upregulation of amino acid catabolism. It suggested a metabolic switch from carbohydrate and lipid to amino acid in these tadpoles. Accordingly, there was a trade-off between protein synthesis and energy production in respect to amino acid allocation, and it provided a metabolic explanation for why protein synthesis was downregulated and growth was suppressed in GBH-stressed tadpoles. In combination with existing literatures, we speculated that GBH might directly target the enzymes in carbohydrate and lipid catabolism, and this metabolic effect of GBH might be common to fish and amphibians. In conclusion, our study provided a systematic insight into the sublethal symptoms of GBH-stressed tadpoles, and a metabolic switch from carbohydrate and lipid to amino acid likely underlay some common toxic symptoms of GBHs on both fish and tadpoles.


Assuntos
Anuros/metabolismo , Metabolismo Energético/efeitos dos fármacos , Glicina/análogos & derivados , Herbicidas/toxicidade , Larva/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Anuros/crescimento & desenvolvimento , Metabolismo Energético/genética , Glicina/toxicidade , Larva/crescimento & desenvolvimento , Larva/metabolismo , Dose Letal Mediana , Biossíntese de Proteínas/efeitos dos fármacos , Biossíntese de Proteínas/genética , Transcriptoma/efeitos dos fármacos
5.
Environ Monit Assess ; 191(10): 608, 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31485806

RESUMO

We assessed whether soil disturbance by agricultural activity influences the growth, development, and survival of individuals in the larval, metamorphic, and postmetamorphic stages of amphibians. Tadpoles of Pithecopus azureus (Cope, 1862) were reared in microcosms assembled with soil from two sites, a pristine site and a rice field. For 5 weeks, we recorded tadpole growth and development as well as physicochemical variable of the water: temperature, conductivity, dissolved oxygen, and pH. The results show that rice field soil produced a level of acidification in the water that influenced the growth and development rates of tadpoles. Tadpoles reared in rice soil had a significantly lower growth rate and body length, and during a specified period, the development rate of the tadpole was significantly lower than that of tadpoles in pristine soil. Overall, tadpoles in rice soil took 3 days longer to reach metamorphosis and 1 additional day to complete metamorphosis compared with tadpoles exposed to pristine soil. Our study shows that disturbed soils modify the physicochemical conditions of temporary ponds, impacting on the initial life stage of the anurans.


Assuntos
Agricultura , Anuros/fisiologia , Meio Ambiente , Solo/química , Animais , Anuros/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Larva/crescimento & desenvolvimento , Traços de História de Vida , Metamorfose Biológica
6.
Ecotoxicology ; 28(6): 707-715, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31250286

RESUMO

Despite the high amphibian biodiversity and increasing pesticide use in tropical countries, knowledge on the sensitivity of tropical amphibians to pesticides remains limited. The aim of this study was to evaluate the acute toxicity of the active ingredients of four of the main herbicides used in Brazilian sugarcane production to tadpoles of two tropical frog species: Physalaemus cuvieri and Hypsiboas pardalis. The calculated 96 h-LC50 (median lethal concentration; in mg a.s./L) values for P. cuvieri and H. pardalis were 4.4 and 7.8 (acetochlor); 15 and <10 (ametryn); 115 and 106 (glyphosate); and 85 and 68 (metribuzin), respectively. These toxicity values demonstrated little interspecies variation and the toxicity of the herbicides appeared to be at least partly related with the respective octanol-water coefficient. Published acute toxicity data of fish and amphibians for herbicides were also compiled from the US-EPA ECOTOX database. These data indicated little difference in herbicide sensitivity between tropical amphibians and both non-tropical amphibians and fish. These findings indicate that temperate (fish and amphibian) herbicide toxicity data are also protective for tropical amphibians. Constraints in such extrapolations and indications for future research are discussed.


Assuntos
Anuros , Herbicidas/toxicidade , Larva/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Animais , Anuros/crescimento & desenvolvimento , Brasil , Larva/crescimento & desenvolvimento , Dose Letal Mediana , Saccharum/crescimento & desenvolvimento , Testes de Toxicidade Aguda
7.
PLoS One ; 14(5): e0215349, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31067224

RESUMO

Ikakogi is a behaviorally and morphologically intriguing genus of glassfrog. Using tadpole morphology, vocalizations, and DNA, a new species is described from the Sierra Nevada de Santa Marta (SNSM), an isolated mountain range in northern Colombia. The new taxon is the second known species of the genus Ikakogi and is morphologically identical to I. tayrona (except for some larval characters) but differs by its genetic distance (14.8% in mitochondrial encoded cytochrome b MT-CYB; ca. 371 bp) and by the dominant frequency of its advertisement call (2928-3273 Hz in contrast to 2650-2870 Hz in I. tayrona). They also differ in the number of lateral buccal floor papillae, and the position of the buccal roof arena papillae. Additionally, the new species is differentiated from all other species of Centrolenidae by the following traits: tympanum visible, vomerine teeth absent, humeral spines present in adult males, bones in life white with pale green in epiphyses, minute punctuations present on green skin dorsum, and flanks with lateral row of small, enameled dots that extend from below eye to just posterior to arm insertion. We describe the external and internal larval morphology of the new species and we redescribe the larval morphology of Ikakogi tayrona on the basis of field collected specimens representing several stages of development from early to late metamorphosis. We discuss the relevance of larval morphology for the taxonomy and systematics of Ikakogi and other centrolenid genera. Finally, we document intraspecific larval variation in meristic characters and ontogenetic changes in eye size, coloration, and labial tooth-rows formulas, and compare tadpoles of related species. Ikakogi tayrona has been proposed as the sister taxon of all other Centrolenidae; our observations and new species description offers insights about the ancestral character-states of adults, egg clutches, and larval features in this lineage of frogs.


Assuntos
Anuros/anatomia & histologia , Animais , Anuros/genética , Anuros/crescimento & desenvolvimento , Tamanho Corporal , Colômbia , Citocromos b/genética , DNA/genética , DNA/metabolismo , Feminino , Larva/anatomia & histologia , Larva/fisiologia , Masculino , Óvulo/fisiologia , Pigmentação da Pele
8.
Proc Biol Sci ; 286(1897): 20182754, 2019 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-30963848

RESUMO

Plasticity-led evolution occurs when a change in the environment triggers a change in phenotype via phenotypic plasticity, and this pre-existing plasticity is subsequently refined by selection into an adaptive phenotype. A critical, but largely untested prediction of plasticity-led evolution (and evolution by natural selection generally) is that the rate and magnitude of evolutionary change should be positively associated with a phenotype's frequency of expression in a population. Essentially, the more often a phenotype is expressed and exposed to selection, the greater its opportunity for adaptive refinement. We tested this prediction by competing against each other spadefoot toad tadpoles from different natural populations that vary in how frequently they express a novel, environmentally induced carnivore ecomorph. As expected, laboratory-reared tadpoles whose parents were derived from populations that express the carnivore ecomorph more frequently were superior competitors for the resource for which this ecomorph is specialized-fairy shrimp. These tadpoles were better at using this resource both because they were more efficient at capturing and consuming shrimp and because they produced more exaggerated carnivore traits. Moreover, they exhibited these more carnivore-like features even without experiencing the inducing cue, suggesting that this ecomorph has undergone an extreme form of plasticity-led evolution-genetic assimilation. Thus, our findings provide evidence that the frequency of trait expression drives the magnitude of adaptive refinement, thereby validating a key prediction of plasticity-led evolution specifically and adaptive evolution generally.


Assuntos
Adaptação Biológica , Adaptação Fisiológica , Anuros/genética , Evolução Biológica , Seleção Genética , Animais , Anuros/crescimento & desenvolvimento , Larva/genética , Larva/crescimento & desenvolvimento , Modelos Biológicos , Fenótipo
9.
PLoS One ; 14(3): e0213426, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30845170

RESUMO

Invasive species and habitat modification threaten California's native pond-breeding amphibians, including the federally threatened California Red-legged Frog (Rana draytonii). The relative contributions of invasive species, including the American Bullfrog (Lithobates catesbeianus), and of habitat changes to these declines are disputed. I conducted a field study over several years in central California to examine the presence/absence of these two species at 79 breeding ponds to determine the predictive role for occupancy of factors including vegetation, pond characteristics, and measures of human activity. I used a boosted regression tree approach to determine the relative value of each predictor variable. Increased measures of human activity, especially proximity to trails and roads, were the best predictors for the absence of California Red-legged Frogs and California Newts. Historical factors and habitat conditions were associated with the extent and spread of the American Bullfrog. The extent and complexity of aquatic macrophytes and pond surface area were good predictors for the presence of these and other amphibian species. Surprisingly, invasive species played a relatively small role in predicting pond occupancy by the native species. These findings can inform conservation and restoration efforts for California Red-legged Frogs, which apparently persist best in small vegetated ponds in areas of low human disturbance.


Assuntos
Anuros/crescimento & desenvolvimento , Animais , Cruzamento/métodos , California , Ecossistema , Humanos , Espécies Introduzidas , Larva/crescimento & desenvolvimento , Tanques
10.
Acta Histochem ; 121(3): 277-283, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30678807

RESUMO

A detailed description of the tegument and parotoid glands of pre-metamorphic, post-metamorphic, juvenile and adult individuals of Rhinella bergi is presented to provide an exhaustive analysis of the integumentary characteristics of this species. Fragments of the tegument were fixed in Bouin solution and preserved in buffered Formol 10%. Subsequently, scanning electron microscopy (SEM) was performed to characterize the macroscopic structure of these regions. Microscopic observations were made from histological sections stained with Hematoxylin and Eosin, Alcian Blue (pH 2,5), PAS-H, Coomassie Blue, Oil Red, and Bielschowsky Impregnation.. There were three types of protuberance: warts, tubers, and thorns. These structures became evident from post-metamorphic stages. The ventral surface shows elevations similar to flat warts; however, tubers and spines are absent. Histologically, each structure consists of a spongy dermis of lax connective tissue and dense and compact dermis, associated with granular glands and a keratinized epidermis. The latter, in the dorsal region, forms projections called thorns. The granular glands accumulate, and their alveoli increase in size progressively. This work provides a morphological and histological description of the integument and the parotoid glands during the larval and post-metamorphic stage of the genus Rhinella, with aspects described for the first time in the genus.


Assuntos
Anuros/crescimento & desenvolvimento , Diferenciação Celular/fisiologia , Células Epidérmicas/citologia , Pele/metabolismo , Animais , Derme/ultraestrutura , Epiderme/ultraestrutura , Imuno-Histoquímica/métodos , Larva/crescimento & desenvolvimento , Microscopia Eletrônica de Varredura/métodos , Pele/patologia
11.
ISME J ; 13(2): 361-373, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30254321

RESUMO

Management of hyper-virulent generalist pathogens is an emergent global challenge, yet for most disease systems we lack a basic understanding as to why some host species suffer mass mortalities, while others resist epizootics. We studied two sympatric species of frogs from the Colombian Andes, which coexist with the amphibian pathogen Batrachochytrium dendrobatidis (Bd), to understand why some species did not succumb to the infection. We found high Bd prevalence in juveniles for both species, yet infection intensities remained low. We also found that bacterial community composition and host defense peptides are specific to amphibian life stages. We detected abundant Bd-inhibitory skin bacteria across life stages and Bd-inhibitory defense peptides post-metamorphosis in both species. Bd-inhibitory bacteria were proportionally more abundant in adults of both species than in earlier developmental stages. We tested for activity of peptides against the skin microbiota and found that in general peptides did not negatively affect bacterial growth and in some instances facilitated growth. Our results suggest that symbiotic bacteria and antimicrobial peptides may be co-selected for, and that together they contribute to the ability of Andean amphibian species to coexist with the global pandemic lineage of Bd.


Assuntos
Anuros/microbiologia , Quitridiomicetos/isolamento & purificação , Microbiota , Peptídeos/farmacologia , Animais , Anuros/crescimento & desenvolvimento , Bactérias/efeitos dos fármacos , Bactérias/isolamento & purificação , Colômbia , Micoses/microbiologia , Micoses/veterinária , Peptídeos/análise , Pele/química , Pele/microbiologia , Simbiose , Simpatria
12.
Environ Sci Pollut Res Int ; 26(3): 2623-2634, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30474816

RESUMO

Amphibians are considered to be excellent bioindicators to their morphophysiological characteristics and life cycle. In this context, the present study investigated the morphological integrity of anuran larvae collected in preserved environments in the Emas National Park, in the municipality of Mineiros (Goiás state, Brazil), and in environments representative of the agricultural matrix of the Rio Verde region, also in Goiás, where there is a long history of the use of agricultural pesticides. Samples of water from temporary ponds, permanent dams, and veredas were analyzed for the presence of pesticides and, especially atrazine (5350 µg/L), found at significantly higher concentrations in the agricultural matrix. We observed a high percentage (approximately 10%) of morphological malformations including alterations of the fins in Boana albopunctatus and Scinax fuscovarius; alteration in oral structures in B. albopunctatus, Dematonotus muelleri, Physalaemus centralis, Physalaemus cuvieri, and Leptodactylus fuscus mainly in the tadpoles collected in the agricultural environment in comparison with those from the protected area (3.5%; P < 0.0001, χ2 31.75). However, changes in the eyes, mouth, intestines, and nostrils, as well as amelia were observed only in the agricultural environment. The vast majority of the observed malformations were associated with the tail and oral disc, which suggests that these anatomical parameters may be used as sensitive morphological biomarkers. Given these findings, we reinforce that areas of agricultural land may have a deleterious effect on the morphological integrity of the tadpoles and consequently, on their development, and that these features may be used as indicators of environmental quality and health.


Assuntos
Anuros/crescimento & desenvolvimento , Monitoramento Ambiental , Animais , Atrazina/análise , Atrazina/farmacologia , Brasil , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Praguicidas/análise , Praguicidas/farmacologia , Tanques/análise , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/farmacologia
14.
Zoolog Sci ; 35(6): 528-534, 2018 12 04.
Artigo em Inglês | MEDLINE | ID: mdl-30520359

RESUMO

Most research on non-consumptive predator effects on amphibian larvae has been conducted in laboratory or mesocosm designs. Here, Pelobates fuscus and Hyla orientalis tadpoles were separately exposed to non-lethal (free-moving, but with tied mouthparts) common carp Cyprinus carpio for one week in enclosures placed in a pond densely stocked with fish. Tadpoles exposed to nonlethal fish did not differ in mortality, body mass, or, except for deeper tail fin depth in P. fuscus, morphological plasticity from controls kept in a fishless pond. Hyla orientalis tadpoles recovered from the fish treatment were subsequently enclosed until metamorphosis in either the pond with fish or the fishless pond. Metamorphs from the pond containing fish were heavier, and did not differ in survivorship or development time from their counterparts initially kept in the fish treatment and then transferred to the fishless pond or from controls kept the entire time under fish-free conditions. The lack of apparent metamorphic costs is consistent with previous experiments on anuran larvae, but the morphological defenses induced (or their absence) are not. In the fish-dominated pond, carp indirectly affected tadpole developmental responses by generating turbidity, through adverse impacts on submerged vegetation and predatory insects, and by increasing food resource (unicellular algae) levels. While the present study does not question the validity of laboratory and mesocosm experiments on the costs of non-consumptive predator effects on amphibian larvae, their outcomes cannot easily be extrapolated to ecologically complex natural habitats.


Assuntos
Anuros/crescimento & desenvolvimento , Carpas/fisiologia , Animais , Comportamento Animal , Ecossistema , Larva/crescimento & desenvolvimento , Metamorfose Biológica , Tanques
15.
Evol Dev ; 20(6): 192-206, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30168254

RESUMO

The acquisition of a movable jaw and a jaw joint are key events in gnathostome evolution. Jaws are derived from the neural crest derived pharyngeal skeleton and the transition from jawless to jawed vertebrates consists of major morphological changes, which must have a genetic foundation. Recent studies on the effects of bapx1 knockdown in fish and chicken indicate that bapx1 has acquired such a role in primary jaw joint development during vertebrate evolution, but evidence from amphibians is missing so far. In the present study, we use Ambystoma mexicanum, Bombina orientalis, and Xenopus laevis to investigate the effects of bapx1 knockdown on the development of these three different amphibians. Using morpholinos we downregulated the expression of bapx1 and obtain morphants with altered mandibular arch morphology. In the absence of bapx1 Meckels cartilage and the palatoquadrate jaw joint initially develop separately but during further development the joint cavity between both fills with chondrocytes. This results in the fusion of both cartilages and the loss of the jaw joint. Despite this the jaw itself remains usable for feeding and breathing. We show that bapx1 plays a role in jaw joint maintenance during development and that the morphants morphology possibly mirrors the morphology of the jawless ancestors of the gnathostomes.


Assuntos
Anuros/crescimento & desenvolvimento , Proteínas de Homeodomínio/metabolismo , Arcada Osseodentária/embriologia , Articulações/embriologia , Ambystoma mexicanum/genética , Ambystoma mexicanum/crescimento & desenvolvimento , Animais , Anuros/classificação , Anuros/genética , Região Branquial/citologia , Região Branquial/metabolismo , Condrócitos/metabolismo , Técnicas de Silenciamento de Genes , Cabeça/embriologia , Proteínas de Homeodomínio/genética , Arcada Osseodentária/metabolismo , Articulações/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteínas de Xenopus/genética , Proteínas de Xenopus/metabolismo , Xenopus laevis/genética , Xenopus laevis/crescimento & desenvolvimento
16.
Am Nat ; 192(4): 461-478, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30205021

RESUMO

When organisms encounter heterogeneous environments, selection may favor the ability of individuals to tailor their phenotypes to suit the prevailing conditions. Understanding the genetic basis of plastic responses is therefore vital for predicting whether susceptible populations can adapt and persist under new selection pressures. Here, we investigated whether there is potential for adaptive plasticity in development time in the quacking frog Crinia georgiana, a species experiencing a drying climate. Using a North Carolina II breeding design, we exposed 90 family groups to two water depth treatments (baseline and low water) late in larval development. We then estimated the contribution of additive and nonadditive sources of genetic variation to early offspring fitness under both environments. Our results revealed a marked decline in larval fitness under the stressful (low water) rearing environment but also that additive genetic variation was negligible for all traits. However, in most cases, we found significant sire-by-dam interactions, indicating the importance of nonadditive genetic variation for offspring fitness. Moreover, sire-by-dam interactions were modified by the treatment, indicating that patterns of nonadditive genetic variance depend on environmental context. For all traits, we found higher levels of nonadditive genetic variation (relative to total phenotypic variation) when larvae were reared under stressful conditions, suggesting that the fitness costs associated with incompatible parental crosses (e.g., homozygous deleterious recessive alleles) will only be expressed when water availability is low. Taken together, our results highlight the need to consider patterns of nonadditive genetic variation under contrasting selective regimes when considering the resilience of species to environmental change.


Assuntos
Anuros/genética , Meio Ambiente , Variação Genética , Animais , Anuros/crescimento & desenvolvimento , Anuros/fisiologia , Corticosterona/análise , Feminino , Fertilização In Vitro/veterinária , Água Doce , Larva/crescimento & desenvolvimento , Larva/fisiologia , Masculino , Óvulo/química
17.
J Morphol ; 279(9): 1269-1281, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30117610

RESUMO

Andean frogs of the genus Telmatobius occur at high elevations, they have an aquatic mode of life and large tadpoles. There are more than 60 species that closely resemble one another and have low values of genetic divergence. However, the skeleton, particularly the cranium, is interspecifically variable with respect to the different levels of development of some elements. Heterochrony is considered to have played a prominent role in generating phenotypic variation, especially among closely related species. Herein, the developmental origins of the adult cranial configuration of two species of Telmatobius are explored. The interactions among larval and postmetamorphic growth, sexual maturation, and ossification sequence in T. oxycephalus and T. rubigo are studied. Although there are no substantial changes in the sequences of ossification of the cranium, it is likely that differential timing of larval periods is related to adult cranial characters. The prolonged larval development of T. rubigo may result in peramorphic configurations of bones that ossify during pre-metamorphosis. This long developmental time would also explain why the gonads of T. rubigo are highly differentiated by the end of metamorphosis. In this species, sexual maturation may be attained precociously in relation to metamorphosis, thereby reducing postmetamorphic developmental time of late-onset bones, which have paedomorphic configurations (e.g., vomer, neopalatine, and columella). An inverse pattern characterizes T. oxycephalus, suggesting that the duration of larval life is related to skeletal configuration in Telmatobius.


Assuntos
Anuros/crescimento & desenvolvimento , Crânio/crescimento & desenvolvimento , Animais , Feminino , Larva/anatomia & histologia , Larva/crescimento & desenvolvimento , Masculino , Tamanho do Órgão , Osteogênese , Ovário/anatomia & histologia
18.
Environ Toxicol Chem ; 37(10): 2699-2704, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30035389

RESUMO

In areas with heavy pesticide use, it is easy to attribute population declines to environmental contamination. The Blanchard's cricket frogs (Acris blanchardi) is an amphibian experiencing declines and range contractions across its distribution in the Midwest Corn Belt (USA). Experimental studies suggest that cricket frogs are sensitive to pesticides, but there are few studies examining this species' susceptibility to contaminants in realistic environments or comparing relative impacts with other anuran species. I reared 3 summer breeding anurans in outdoor mesocosms posthatching through metamorphosis to examine the effects of 2 insecticides (imidacloprid and carbaryl) and 1 herbicide (glyphosate with polyoxyethylene tallow amine) on larval development and metamorphosis. Cricket frogs were positively affected by insecticide exposure, likely a result of changes in the food web that increased food abundance. However, metamorphosis of green frogs (Lithobates clamitans) and gray tree frogs (Hyla chrysoscelis) appeared unaffected by pesticide exposure. The results of the present study suggest that the impacts of pesticides alone are unlikely to have population-level impacts for the anurans examined. Environ Toxicol Chem 2018;37:2699-2704. © 2018 SETAC.


Assuntos
Anuros/crescimento & desenvolvimento , Ecossistema , Praguicidas/toxicidade , Rana clamitans/crescimento & desenvolvimento , Análise de Variância , Animais , Carbaril/toxicidade , Exposição Ambiental/análise , Glicina/análogos & derivados , Glicina/toxicidade , Herbicidas/toxicidade , Inseticidas/toxicidade , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Neonicotinoides/toxicidade , Nitrocompostos/toxicidade , Polietilenoglicóis/toxicidade , Especificidade da Espécie , Fatores de Tempo
19.
BMC Genomics ; 19(1): 507, 2018 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-29954327

RESUMO

BACKGROUND: Anuran metamorphosis, which is obligatorily initiated and sustained by thyroid hormone (TH), is a dramatic example of extensive morphological, biochemical and cellular changes occurring during post-embryonic development. Thus, it provides an ideal model to understand the actions of the hormone and molecular mechanisms underlying these developmental and apoptotic processes. In addition to transcriptional factors, microRNAs (miRNAs) play key roles in diverse biological processes via post-transcriptional repression of mRNAs. However, the possible role of miRNAs in anuran metamorphosis is not well understood. Screening and identification of TH-responding miRNAs are required to reveal the integrated regulatory mechanisms of TH during metamorphosis. Given the specific role of TRs during M. fissipes metamorphosis and the characteristics of M. fissipes as an ideal model, Illumina sequencing technology was employed to get a full scope of miRNA in M. fissipes metamorphosis treated by T3. RESULTS: Morphological and histological analysis revealed that 24 h T3 treatment M. fissipes tadpoles resembled that at the climax of natural metamorphosis. Thus, small RNA libraries were constructed from control and 24 h T3 treatment groups. A total of 164 conserved miRNAs and 36 predicted novel miRNAs were characterized. Furthermore, 5' first and ninth nucleotides of miRNAs were significantly enriched in U in our study. In all, 21 miRNAs were differentially expressed between the T3 and control groups (p < 0.01). A total of 10,206 unigenes were identified as target genes of these differentially expressed miRNAs. KEGG pathway analysis indicated that the most overrepresented miRNA target genes were enriched in the "PI3k-Akt signaling pathway". In addition, a network associated with the TH signaling pathway provides an opportunity to further understand the complex biological processes that occur in metamorphosis. CONCLUSIONS: We identified a large number of miRNAs during M. fissipes metamorphosis, and 21 of them were differentially expressed in the two groups that represented two different metamorphic stages. These miRNAs may play important roles during metamorphosis. The study gives us clues for further studies of the mechanisms of anuran metamorphosis and provides a model to study the mechanism of TH-affected biological processes in humans.


Assuntos
Anuros/genética , Metamorfose Biológica/genética , MicroRNAs/genética , Hormônios Tireóideos/metabolismo , Animais , Anuros/crescimento & desenvolvimento , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Intestinos/patologia , Larva/efeitos dos fármacos , Larva/genética , Masculino , Metamorfose Biológica/efeitos dos fármacos , MicroRNAs/metabolismo , Fosfatidilinositol 3-Quinases/genética , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/efeitos dos fármacos , Tri-Iodotironina/farmacologia
20.
Mol Ecol ; 27(14): 3001-3015, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29862607

RESUMO

Molecular technologies have revolutionized our classification of animal mating systems, yet we still know very little about the genetic mating systems of many vertebrate groups. It is widely believed that anuran amphibians have the highest reproductive diversity of all vertebrates, yet genetic mating systems have been studied in <1% of all described species. Here, we use single nucleotide polymorphisms to quantify the genetic mating system of the terrestrial breeding red-backed toadlet Pseudophryne coriacea. In this species, breeding is prolonged (approximately 5 months), and males construct subterranean nests in which females deposit eggs. We predicted that females would display extreme sequential polyandry because this mating system has been reported in a closely related species (P. bibronii). Parentage analysis revealed that mating success was heavily skewed towards a subset of males (30.6% of potential sires) and that nearly all females (92.6%) mated with one male. In a high percentage of occupied nests (37.1%), the resident male was not the genetic sire, and very few nests (4.3%) contained clutches with multiple paternity. Unexpectedly, these results show that sequential polyandry is rare. They also show that there is a high frequency of nest takeover and extreme competition between males for nest sites, but that males rarely sneak matings. Genetic analysis also revealed introgressive hybridization between P. coriacea and the red-crowned toadlet (Pseudophryne australis). Our study demonstrates a high level of mating system complexity, and it shows that closely related anurans can vary dramatically in their genetic mating system.


Assuntos
Anuros/genética , Reprodução/genética , Comportamento Sexual Animal/fisiologia , Animais , Anuros/crescimento & desenvolvimento , Cruzamento , Feminino , Marcadores Genéticos , Masculino , Polimorfismo de Nucleotídeo Único/genética
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