RESUMO
Amidst a global amphibian decline, captive breeding has become an important component of many conservation management programs. Some species fail to readily reproduce in captivity, including leiopelmatid frogs, an archaic lineage endemic to New Zealand. Assisted reproductive technologies can improve the reproductive potential and genetic management of captive programs. Herein we describe efforts to induce spermiation and mating in the threatened Hamilton's frog Leiopelma hamiltoni using a gonadotrophin-releasing hormone agonist and human chorionic gonadotrophin. The spermiation response was poor, with few individuals releasing spermatozoa and a low sperm concentration (mean (±s.e.) 27.4±8.5×103 spermatozoa mL-1 ) when spermiation was stimulated. The sperm concentration peaked 12-24h after hormone administration, suggesting this species may be slower to react than other anurans. Spermic urine was present in five males before hormone treatment. The sperm concentration was higher in this group (128.7±54.9×103 spermatozoa mL-1 ) than in the hormone-induced males. All spermatozoa observed exhibited no motility or, at most, a limited swaying movement with no forward progression. In separate hormone induction trials with 60 individuals (two males to one female per trial), no mating was exhibited during the 12h after treatment. Further studies to hormonally stimulate gamete release and mating are needed in leiopelmatids.
Assuntos
Anuros , Espermatozoides , Animais , Anuros/fisiologia , Gonadotropina Coriônica/farmacologia , Feminino , Masculino , Reprodução , Contagem de EspermatozoidesRESUMO
The global reach of zoos has enormous potential to raise awareness of conservation issues such as the amphibian extinction crisis. One mechanism of achieving this is through targeted, time-limited campaigns. However, the longer-term impact of such campaigns on conservation outcomes is rarely evaluated. The goal of this study is to evaluate how zoos view "The Year of The Frog," a campaign launched by zoos in 2008, with the aim of raising awareness of the global amphibian crisis and generating funds to support amphibian conservation initiatives. A questionnaire-based survey of 43 zoos from fourteen countries was used to evaluate how zoo practitioners believed the campaign influenced amphibian conservation some 10 years after its launch. Survey results showed that the campaign not only contributed to the improvement of research into amphibian husbandry in zoos but also increased support of in situ conservation of amphibians. Zoos focused on exotic species, but developed countries led most of the actions of the campaign. The campaign has inspired and encouraged some zoos and other ex situ conservation organizations to embrace amphibian conservation. The next step is to increase collaboration with more organizations through, for example, AArk and IUCN SSC/ASG, particularly in countries that have high amphibian biodiversity.
Assuntos
Conservação dos Recursos Naturais , Espécies em Perigo de Extinção , Animais , Animais de Zoológico , Anuros , Biodiversidade , Conservação dos Recursos Naturais/métodosRESUMO
Emerging infectious diseases are on the rise in many different taxa, including, among others, the amphibian batrachochytrids, the snake fungal disease and the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) virus, responsible for Coronavirus disease 2019 (COVID-19) in mammals. Following the onset of the pandemic linked to COVID-19, eastern Asia has shown strong leadership, taking actions to regulate the trade of potential vector species in several regions. These actions were taken in response to an increase in public awareness, and the need for a quick reaction to mitigate against further pandemics. However, trade restrictions rarely affect amphibians, despite the risk of pathogen transmission, directly, or indirectly through habitat destruction and the loss of vector consumption. Thus, species that help alleviate the risk of zoonoses or provide biological control are not protected. Hence, in view of the global amphibian decline and the risk of zoonoses, we support the current wildlife trade regulations and support measures to safeguard wildlife from overexploitation. The current period of regulation overhaul should be used as a springboard for amphibian conservation. To mitigate risks, we suggest the following stipulations specifically for amphibians. I) Restrictions to amphibian farming in eastern Asia, in relation to pathogen transmission and the establishment of invasive species. II) Regulation of the amphibian pet trade, with a focus on potential vector species. III) Expansion of the wildlife trade ban, to limit the wildlife-human-pet interface. The resulting actions will benefit both human and wildlife populations, as they will lead to a decrease in the risk of zoonoses and better protection of the environment. SIGNIFICANCE STATEMENT: There is an increasing number of emerging infectious diseases impacting all species, including amphibians, reptiles and mammals. The latest threat to humans is the virus responsible for COVID-19, and the resulting pandemic. Countries in eastern Asia have taken steps to regulate wildlife trade and prevent further zoonoses thereby decreasing the risk of pathogens arising from wild species. However, as amphibians are generally excluded from regulations we support specific trade restrictions: I) Restrictions to amphibian farming; II) regulation of the amphibian pet trade; III) expansion of the wildlife trade ban. These restrictions will benefit both human and wildlife populations by decreasing the risks of zoonoses and better protecting the environment.
RESUMO
Amphibian skin is highly variable in structure and function across anurans, and plays an important role in physiological homeostasis and immune defence. For example, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis ( Bd), but interspecific variation in sloughing frequency is largely unknown. Using phylogenetic linear mixed models, we assessed the relationship between skin turnover rate, skin morphology, ecological traits and overall evidence of Bd-driven declines. We examined skin sloughing rates in 21 frog species from three continents, as well as structural skin characteristics measured from preserved specimens. We found that sloughing rate varies significantly with phylogenetic group, but was not associated with evidence of Bd-driven declines, or other skin characteristics examined. This is the first comparison of sloughing rate across a wide range of amphibian species, and creates the first database of amphibian sloughing behaviour. Given the strong phylogenetic signal observed in sloughing rate, approximate sloughing rates of related species may be predicted based on phylogenetic position. While not related to available evidence of declines, understanding variation in sloughing rate may help explain differences in the severity of infection in genera with relatively slow skin turnover rates (e.g. Atelopus).
Assuntos
Anuros , Quitridiomicetos/fisiologia , Dermatomicoses/veterinária , Pele/microbiologia , Animais , Anuros/fisiologia , Dermatomicoses/fisiopatologia , FilogeniaRESUMO
Despite the global declines in the rate of amphibians, evaluation of public understanding of the crisis has not yet been carried out. We surveyed visitors (n = 1,293) at 15 zoos in Brazil, New Zealand, and the United Kingdom, using a certainty-based assessment method to compare visitor knowledge of the global amphibian crisis. We further analyzed zoo educational material about amphibians to explore its potential to raise awareness through amphibian-focused environmental education. Visitors in the three countries had relatively little understanding of amphibians and the global amphibian crisis. When the degree of confidence in answering the questions (high, medium, and low) is accounted for, correct answers varied between 28% and 39%. This compared to scores of between 58% and 73% when the degree of confidence in responding was not accounted for. However, specific areas of knowledge (e.g., biology, conservation, biogeography, and conceptual ideas) varied significantly across the countries. Visitors had a weaker grasp of biogeographical and conservation issues than general amphibian biology. Zoo visitors in Brazil knew less about amphibian conservation than those in New Zealand or the United Kingdom. There was less amphibian-focused content in educational materials in zoos in Brazil than there was in the United Kingdom. Improving information about the global amphibian crisis may increase support for future conservation actions. Outreach education is one of the most important approaches in any strategic planning for conservation of species. Amphibian-focused environmental education at institutions such as zoos and aquaria can be a crucial intervention to support amphibian conservation worldwide.
Assuntos
Anfíbios , Conservação dos Recursos Naturais , Adolescente , Adulto , Animais , Brasil , Coleta de Dados , Humanos , Nova Zelândia , Dinâmica Populacional , Reino Unido , Adulto JovemRESUMO
BACKGROUND: The New Zealand native frogs, family Leiopelmatidae, are among the most archaic in the world. Leiopelma hochstetteri (Hochstetter's frog) is a small, semi-aquatic frog with numerous, fragmented populations scattered across New Zealand's North Island. We characterized a major histocompatibility complex (MHC) class II B gene (DAB) in L. hochstetteri from a spleen transcriptome, and then compared its diversity to neutral microsatellite markers to assess the adaptive genetic diversity of five populations ("evolutionarily significant units", ESUs). RESULTS: L. hochstetteri possessed very high MHC diversity, with 74 DAB alleles characterized. Extremely high differentiation was observed at the DAB locus, with only two alleles shared between populations, a pattern that was not reflected in the microsatellites. Clustering analysis on putative peptide binding residues of the DAB alleles indicated four functional supertypes, all of which were represented in 4 of 5 populations, albeit at different frequencies. Otawa was an exception to these observations, with only two DAB alleles present. CONCLUSIONS: This study of MHC diversity highlights extreme population differentiation at this functional locus. Supertype differentiation was high among populations, suggesting spatial and/or temporal variation in selection pressures. Low DAB diversity in Otawa may limit this population's adaptive potential to future pathogenic challenges.
Assuntos
Proteínas de Anfíbios/genética , Anuros/genética , Anuros/imunologia , Espécies em Perigo de Extinção , Antígenos de Histocompatibilidade Classe II/genética , Sequência de Aminoácidos , Animais , Variação Genética , Repetições de Microssatélites , Dados de Sequência Molecular , Nova Zelândia , Alinhamento de SequênciaRESUMO
This report describes the investigations into the cause and treatment of metabolic bone disease (MBD) in captive native New Zealand frogs (Leiopelma spp.) and the role of fluoride in the disease. MBD was diagnosed in Leiopelma archeyi and Leiopelma hochstetteri in 2008 at three institutions: Auckland Zoo, Hamilton Zoo, and the University of Otago. Most of these frogs had originally been held at the University of Canterbury for several years (2000-2004) but some were collected directly from the wild. Radiographs on archived and live frogs showed that MBD had been present at Canterbury, but at a lower rate (3%) than in the current institutions (38-67%). Microcomputed tomography showed that the femoral diaphyses of the captive frogs at Auckland Zoo had greater bone volume, bone surface, cross-sectional thickness, and mean total cross-sectional bone perimeter, which is consistent with osteofluorosis. On histology of the same femurs, there was hyperplasia, periosteal growth, and thickening of trabeculae, which are also consistent with skeletal fluorosis. An increase in fluoride levels in the water supply preceded the rise in the incidence of the above pathology, further supporting the diagnosis of osteofluorosis. Analysis of long-standing husbandry practices showed that ultraviolet B (UVB) exposure and the dietary calcium:phosphorus ratio were deficient when compared with wild conditions-likely causing chronic underlying MBD. To prevent multifactorial MBD in captive Leiopelma, the authors recommend increasing dietary calcium by incorporating into the captive diet inherently calcium-rich invertebrates; increasing exposure to natural or artificial (UVB) light; and using defluoridated water. Addressing these three factors at Auckland Zoo reduced morbidity, bone fractures, and mortality rates.
Assuntos
Anuros , Doenças Ósseas Metabólicas/veterinária , Fluoretos/efeitos adversos , Animais , Animais de Zoológico , Doenças Ósseas Metabólicas/induzido quimicamente , Doenças Ósseas Metabólicas/tratamento farmacológico , Doenças Ósseas Metabólicas/patologia , Cálcio/administração & dosagem , Cálcio/uso terapêutico , Colecalciferol/administração & dosagem , Colecalciferol/uso terapêutico , Suplementos Nutricionais , Nova Zelândia , Estudos RetrospectivosRESUMO
As a result of global declines in amphibian populations, interest in the conservation of amphibians has grown. This growth has been fueled partially by the recent discovery of other potential causes of declines, including chytridiomycosis (the amphibian chytrid, an infectious disease) and climate change. It has been proposed that researchers have shifted their focus to these novel stressors and that other threats to amphibians, such as habitat loss, are not being studied in proportion to their potential effects. We tested the validity of this proposal by reviewing the literature on amphibian declines, categorizing the primary topic of articles within this literature (e.g., habitat loss or UV-B radiation) and comparing citation rates among articles on these topics and impact factors of journals in which the articles were published. From 1990 to 2009, the proportion of papers on habitat loss remained fairly constant, and although the number of papers on chytridiomycosis increased after the disease was described in 1998, the number of published papers on amphibian declines also increased. Nevertheless, papers on chytridiomycosis were more highly cited than papers not on chytridiomycosis and were published in journals with higher impact factors on average, which may indicate this research topic is more popular in the literature. Our results were not consistent with a shift in the research agenda on amphibians. We believe the perception of such a shift has been supported by the higher citation rates of papers on chytridiomycosis.
Assuntos
Anfíbios/fisiologia , Bases de Dados Bibliográficas/estatística & dados numéricos , Extinção Biológica , Fator de Impacto de Revistas , Dinâmica Populacional , Animais , Ecossistema , Micoses/epidemiologia , Micoses/veterinária , Raios Ultravioleta/efeitos adversosRESUMO
The dissemination of the virulent pathogen Batrachochytrium dendrobatidis (Bd) has contributed to the decline and extinction of many amphibian species worldwide. Several different strains have been identified, some of which are sympatric. Interactions between co-infecting strains of a pathogen can have significant influences on disease epidemiology and evolution; therefore the dynamics of multi-strain infections is an important area of research. We stained Bd cells with 2 fluorescent BODIPY fatty acid probes to determine whether these can potentially be used to distinguish and track Bd cell lines in multi-strain experiments. Bd cells in broth culture were stained with 5 concentrations of green-fluorescent BODIPY FL and red-fluorescent BODIPY 558/568 and visualised under an epifluorescent microscope for up to 16 d post-dye. Dyed strains were also assessed for growth inhibition. The most effective concentration for both dyes was 10 pM. This concentration of dye produced strong fluorescence for 12 to 16 d in Bd cultures held at 23 degrees C (3 to 4 generations), and did not inhibit Bd growth. Cells dyed with BODIPY FL and BODIPY 558/568 can be distinguished from each other on the basis of their fluorescence characteristics. Therefore, it is likely that this technique will be useful for research into multi-strain dynamics of Bd infections.
Assuntos
Anfíbios/microbiologia , Quitridiomicetos/isolamento & purificação , Corantes Fluorescentes , Animais , Compostos de Boro , Quitridiomicetos/classificaçãoRESUMO
All frogs are assumed to jump in a similar manner by rapidly extending hindlimbs during the propulsive phase and rotating the limbs forward during flight in order to land forelimbs first. However, studies of jumping behavior are lacking in the most primitive living frogs of the family Leiopelmatidae. These semi-aquatic or terrestrial anurans retain a suite of plesiomorphic morphological features and are unique in using an asynchronous (trot-like) rather than synchronous "frog-kick" swimming gait of other frogs. We compared jumping behavior in leiopelmatids to more derived frogs and found that leiopelmatids maintain extended hindlimbs throughout flight and landing phases and do not land on adducted forelimbs. These "belly-flop" landings limit the ability for repeated jumps and are consistent with a riparian origin of jumping in frogs. The unique behavior of leiopelmatids shows that frogs evolved jumping before they perfected landing. Moreover, an inability to rapidly cycle the limbs may provide a functional explanation for the absence of synchronous swimming in leiopelmatids.
Assuntos
Anuros/fisiologia , Membro Anterior/fisiologia , Marcha/fisiologia , Locomoção/fisiologia , Animais , Articulação do Tornozelo/fisiologia , Fenômenos Biomecânicos/fisiologia , Feminino , Articulações/fisiologia , Masculino , Natação , Gravação em Vídeo/métodosRESUMO
The susceptibility of Archey's frog Leiopelma archeyi to Batrachochytrium dendrobatidis (Bd) is unknown, although one large population is thought to have declined sharply due to chytridiomycosis. As primary infection experiments were not permitted in this endangered New Zealand species, 6 wild-caught L. archeyi that naturally cleared infections with Bd while in captivity were exposed again to Bd to assess their immunity. These frogs were from an infected population at Whareorino, which has no known declines. All 6 L. archeyi became reinfected at low intensities, but rapidly self cured, most by 2 wk. Six Litoria ewingii were used as positive controls and developed heavier infections and clinical signs by 3 wk, demonstrating that the zoospore inoculum was virulent. Six negative controls of each species remained uninfected and healthy. Our results show that L. archeyi that have self cured have resistance to chytridiomycosis when exposed. The pattern is consistent with innate or acquired immunity to Bd, and immunological studies are needed to confirm this.
Assuntos
Quitridiomicetos/fisiologia , Micoses/veterinária , Ranidae , Animais , Micoses/imunologia , Micoses/microbiologiaRESUMO
Translocations are important tools in the field of conservation. Despite increased use over the last few decades, the appropriateness of translocations for amphibians and reptiles has been debated widely over the past 20 years. To provide a comprehensive evaluation of the suitability of amphibians and reptiles for translocation, we reviewed the results of amphibian and reptile translocation projects published between 1991 and 2006. The success rate of amphibian and reptile translocations reported over this period was twice that reported in an earlier review in 1991. Success and failure rates were independent of the taxonomic class (Amphibia or Reptilia) released. Reptile translocations driven by human-wildlife conflict mitigation had a higher failure rate than those motivated by conservation, and more recent projects of reptile translocations had unknown outcomes. The outcomes of amphibian translocations were significantly related to the number of animals released, with projects releasing over 1000 individuals being most successful. The most common reported causes of translocation failure were homing and migration of introduced individuals out of release sites and poor habitat. The increased success of amphibian and reptile translocations reviewed in this study compared with the 1991 review is encouraging for future conservation projects. Nevertheless, more preparation, monitoring, reporting of results, and experimental testing of techniques and reintroduction questions need to occur to improve translocations of amphibians and reptiles as a whole.
Assuntos
Anfíbios/fisiologia , Conservação dos Recursos Naturais/métodos , Ecossistema , Répteis/fisiologia , Manejo de Espécimes/métodos , AnimaisRESUMO
Archey's frog Leiopelma archeyi is a critically endangered New Zealand endemic species. The discovery of the emerging infectious disease, chytridiomycosis, in wild populations of this frog raised concern that this disease may drive the species to extinction. Twelve wild-caught Archey's frogs naturally infected with the amphibian chytrid fungus Batrachochytrium dendrobatidis were monitored in captivity by observing clinical signs, measuring weight gain, and performing repeated PCR tests. Eight frogs were treated with topical chloramphenicol, without PCR results being available, for B. dendrobatidis at the day of entry of the frog into the trial. Eleven of the 12 frogs (92%) cleared their infection within 3 mo of capture, even though they were held at 15 degrees C and in high humidity, conditions that are ideal for the survival and propagation of B. dendrobatidis. B. dendrobatidis in the remaining frog tested positive for the fungus was eliminated after treatment with topical chloramphenicol. None of the 8 frogs exposed to chloramphenicol showed any acute adverse reactions. Archey's frog appears to have a low level of susceptibility to the clinical effects of chytridiomycosis. Individual frogs can eliminate B. dendrobatidis and Archey's frog can apparently be treated with topical chloramphenicol with no acute adverse reactions. However, the small number of specimens treated here requires that more extensive testing be done to confirm the safety of chloramphenicol. The significance of the amphibian chytrid fungus for wild populations of Archey's frog needs to be determined by a longitudinal study in an infected wild population to correlate the presence of B. dendrobatidis in individual frogs. Such a study should occur over a period of at least 3 yr with clinical assessment and monitoring of survival, growth and body condition parameters.
Assuntos
Anuros/microbiologia , Quitridiomicetos/fisiologia , Administração Tópica , Animais , Antifúngicos/administração & dosagem , Antifúngicos/farmacologia , Cloranfenicol/administração & dosagem , Cloranfenicol/farmacologia , Quitridiomicetos/efeitos dos fármacosRESUMO
The decline of amphibians has been of international concern for more than two decades, and the global spread of introduced fauna is a major factor in this decline. Conservation management decisions to implement control of introduced fauna are often based on diet studies. One of the most common metrics to report in diet studies is Frequency of Occurrence (FO), but this can be difficult to interpret, as it does not include a temporal perspective. Here, we examine the potential for FO data derived from molecular diet analysis to inform invasive species management, using invasive ship rats (Rattus rattus) and endemic frogs (Leiopelma spp.) in New Zealand as a case study. Only two endemic frog species persist on the mainland. One of these, Leiopelma archeyi, is Critically Endangered (IUCN 2017) and ranked as the world's most evolutionarily distinct and globally endangered amphibian (EDGE, 2018). Ship rat stomach contents were collected by kill-trapping and subjected to three methods of diet analysis (one morphological and two DNA-based). A new primer pair was developed targeting all anuran species that exhibits good coverage, high taxonomic resolution, and reasonable specificity. Incorporating a temporal parameter allowed us to calculate the minimum number of ingestion events per rat per night, providing a more intuitive metric than the more commonly reported FO. We are not aware of other DNA-based diet studies that have incorporated a temporal parameter into FO data. The usefulness of such a metric will depend on the study system, in particular the feeding ecology of the predator. Ship rats are consuming both species of native frogs present on mainland New Zealand, and this study provides the first detections of remains of these species in mammalian stomach contents.
RESUMO
Many animals use sounds produced by conspecifics for mate identification. Female insects and anuran amphibians, for instance, use acoustic cues to localize, orient toward and approach conspecific males prior to mating. Here we present a novel technique that utilizes multiple, distributed sound-indication devices and a miniature LED backpack to visualize and record the nocturnal phonotactic approach of females of the Australian orange-eyed tree frog (Litoria chloris) both in a laboratory arena and in the animal's natural habitat. Continuous high-definition digital recording of the LED coordinates provides automatic tracking of the female's position, and the illumination patterns of the sound-indication devices allow us to discriminate multiple sound sources including loudspeakers broadcasting calls as well as calls emitted by individual male frogs. This innovative methodology is widely applicable for the study of phonotaxis and spatial structures of acoustically communicating nocturnal animals.
Assuntos
Anuros/fisiologia , Tecnologia de Sensoriamento Remoto/instrumentação , Vocalização Animal , Animais , Escuridão , Ecossistema , FemininoRESUMO
Amphibians are currently the most threatened group of vertebrates worldwide, and introduced fauna play a major role in their decline. The control of introduced predators to protect endangered species is often based on predation rates derived from diet studies of predators, but prey detection probabilities using different techniques are variable. We measured the detectability of frogs as prey, using morphological and DNA-based diet analyses, in the stomachs and faeces of four mammal species that have been introduced to many areas of the world. Frogs (Litoria raniformis) were fed to rats (Rattus norvegicus and R. rattus), mice (Mus musculus) and hedgehogs (Erinaceus europaeus). DNA-based analysis outperformed morphological analysis, increasing the prey detection rate from 2% to 70% in stomachs and from 0% to 53% in faeces. In most cases, utilizing either stomachs or faeces did not affect the success of prey DNA detection; however, using faeces extended the detectability half-life from 7 to 21 h. This study is the first to measure prey DNA detection periods in mammalian stomachs, and the first to compare prey DNA detection periods in the stomachs and faeces of vertebrates. The results indicate that DNA-based diet analysis provides a more reliable approach for detecting amphibians as prey and has the potential to be used to estimate the rate of predation by introduced mammals on endangered amphibians.
Assuntos
Anuros/anatomia & histologia , Anuros/genética , DNA/genética , Comportamento Alimentar , Mamíferos/fisiologia , Animais , DNA/isolamento & purificação , Fezes , Ouriços , Camundongos , Dados de Sequência Molecular , Ratos , Análise de Sequência de DNA , EstômagoRESUMO
Movements and locomotor behaviour were studied in the most basal living frog family (Leiopelmatidae: Ascaphus+Leiopelmatidae), which includes two stream-dwelling species and several that have transitioned into terrestrial niches. These cryptic frogs remain immobile over 99.6% of the time above ground as they sit in wait of prey and only rarely use jumping to escape. Walking is their primary mode of locomotion. The two stream species, which are separated by deep time and extreme geographic distance, have nearly identical behavioural repertoires and locomotor performance, which included occasional jumping as a means to change foraging positions. The terrestrial species, one of which has become semi-arboreal, rarely jump in nature and rely on chemical and postural antipredator behaviours to avoid predation. If early frogs resembled leiopelmatids, they were not well versed in jumping. Locomotor behaviour and performance of leiopelmatid frogs do not support the hypothesis that frog jumping originally evolved primarily as a means to rapidly escape into water. Given the basal position of the leiopelmatids, the locomotor strategy of these cryptic, cold-adapted, belly-flopping anurans that usually walk may represent a successful initial step in the evolution of saltatorial locomotion in frogs.
Assuntos
Anuros/fisiologia , Movimento/fisiologia , Comportamento Predatório/fisiologia , Animais , Comportamento Animal , Comportamento Alimentar , Locomoção/fisiologiaRESUMO
Abstract Knowledge of baseline cutaneous bacterial microbiota may be useful in interpreting diagnostic cultures from captive sick frogs and as part of quarantine or pretranslocation disease screening. Bacteria may also be an important part of innate immunity against chytridiomycosis, a fungal skin disease caused by Batrachochytrium dendrobatidis (Bd). In February 2009, 92 distinct bacterial isolates from the ventral skin of 64 apparently healthy Leiopelma archeyi and Leiopelma hochstetteri native frogs from the Coromandel and Whareorino regions in New Zealand were identified using molecular techniques. The most-common isolates identified in L. archeyi were Pseudomonas spp. and the most common in L. hochstetteri were Flavobacterium spp. To investigate the possible role of bacteria in innate immunity, a New Zealand strain of Bd (Kaikorai Valley-Lewingii-2008-SDS1) was isolated and used in an in vitro challenge assay to test for inhibition by bacteria. One bacterial isolate, a Flavobacterium sp., inhibited growth of Bd. These results imply that diverse cutaneous bacteria are present and may play a role in the innate defense in Leiopelma against pathogens, including Bd, and are a starting point for further investigation.
Assuntos
Bactérias/isolamento & purificação , Quitridiomicetos/fisiologia , Ranidae/microbiologia , Pele/microbiologia , Animais , Bactérias/classificação , Quitridiomicetos/genética , Nova Zelândia , FilogeniaRESUMO
Endemic New Zealand frogs of the genus Leiopelma are from a basal lineage of extant anurans that release defensive secretions onto their skin when disturbed. Here, we characterize the gross anatomy and microscopic structure of the skin of L. archeyi, L. hochstetteri, and L. pakeka using stereoscopic, light and transmission electron microscopy. The terrestrial L. archeyi and L. pakeka possess dimorphic granular glands, categorized as type I and II, based on their frequency and morphological traits, whereas the semi-aquatic L. hochstetteri lacks type I glands. This is the first report of differential dimorphism in anurans of the same genus. This dimorphism could be interpreted as an adaptation to different physiological or ecological needs of these species. However, species within this ancient genus share similar general gland morphology with other anurans, namely, a secretory unit containing storage granules ensheathed by myoepithelial cells. Type I glands are ellipsoid, large and contain a homogeneous mass of electron-dense granules (1.8 ± 0.08 µm in diameter). Type II glands are round and contain larger heterogeneous granules (4.06 ± 0.16 µm) of varying densities. Exposure to noradrenaline causes the contraction of myoepithelial cells, resulting in bulk discharge of type I glands through the epidermal duct onto the skin surface. Differential release of secretions from dimorphic glands may be indicative of their functional specialisation in antipredatory or regulative roles. Mass spectrometric techniques were used to de novo sequence peptides present in the skin secretions of Leiopelma species. A total of 30 previously undescribed peptides from Leiopelma species were fully or partially sequenced. These peptides exhibited no similarity to any known compounds.
Assuntos
Anuros/anatomia & histologia , Sequência de Aminoácidos , Animais , Anuros/metabolismo , Feminino , Masculino , Microscopia Eletrônica de Transmissão , Dados de Sequência Molecular , Nova Zelândia , Norepinefrina/farmacologia , Peptídeos/química , Peptídeos/metabolismo , Vesículas Secretórias/química , Vesículas Secretórias/efeitos dos fármacos , Vesículas Secretórias/ultraestrutura , Pele/anatomia & histologia , Pele/ultraestruturaRESUMO
The brown tree frog (Litoria ewingii) is the only known Southern Hemisphere vertebrate that can survive full-body freezing. Freezing challenges living organisms in many ways, with ice formation in the body producing a suite of physical and metabolic stresses which can damage cells and tissues. The present study looked at two mechanisms that address some of these stresses: cryoprotectants and ice nucleating agents (INAs). Skin secretions from L. ewingii were sampled along with microhabitat substrate and tested for the presence of INAs, which help control ice formation in the body. L. ewingii plasma was tested for seasonal and freezing-induced changes in both glucose and glycerol, which may have a cryoprotective role in freezing-tolerant frogs. Glycerol levels increased on freezing and decreased on thawing, while glucose levels did not change on freezing but increased on thawing. This suggests that glycerol may be acting as a cryoprotectant, although levels are low compared to other frogs. A clear seasonal change was seen in INA activity, with greater activity in winter than in summer. While potent INAs came from the microhabitat substrate, this work has shown for the first time that skin secretions also contain active INAs.