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Environmental temperature strongly influences the adaptation dynamics of amphibians, whose limited regulation capabilities render them susceptible to thermal oscillations. A central element of the adaptive strategies is the transcription factors (TFs), which act as master regulators that orchestrate stress responses, enabling species to navigate the fluctuations of their environment skillfully. Our study delves into the intricate relationship between TF expression and thermal adaptation mechanisms in the Rhinella spinulosa populations. We sought to elucidate the dynamic modulations of TF expression in prometamorphic and metamorphic tadpoles that inhabit two thermally contrasting environments (Catarpe and El Tatio Geyser, Chile) and which were exposed to two thermal treatments (25 °C vs. 20 °C). Our findings unravel an intriguing dichotomy in response strategies between these populations. First, results evidence the expression of 1374 transcription factors. Regarding the temperature shift, the Catarpe tadpoles show a multifaceted approach by up-regulating crucial TFs, including fosB, atf7, and the androgen receptor. These dynamic regulatory responses likely underpin the population's ability to navigate thermal fluctuations effectively. In stark contrast, the El Tatio tadpoles exhibit a more targeted response, primarily up-regulating foxc1. This differential expression suggests a distinct focus on specific TFs to mitigate the effects of temperature variations. Our study contributes to understanding the molecular mechanisms governing thermal adaptation responses and highlights the resilience and adaptability of amphibians in the face of ever-changing environmental conditions.

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The aim of this study was to characterize an aquatic system of Santa Fe province (Argentina) receiving wastewater from agro-industrial activities (mainly dairy) by in situ assessment (fauna mortality, physicochemical, microbiological, and pesticide residues measurement), and ecotoxicity bioassays on amphibian tadpoles. Water and sediment samples were obtained from the Los Troncos Stream (LTS), previous to the confluence with the "San Carlos" drainage channel (SCC), and from the SCC. Biological parameters (mortality and sublethal biomarkers) were used to evaluate ecotoxicity during 10-day exposure of Rhinella arenarum tadpoles to LTS and SCC samples. Nine pesticides were detected in both LTS and SCC. Chemical and biochemical oxygen demand, ammonia, and coliform count recorded in SCC greatly exceeded limits for aquatic life protection. At SCC and LTS after the confluence with SCC, numerous dying and dead aquatic turtles (Phrynops hilarii) were recorded. In the ecotoxicity assessment, no mortality of tadpoles was observed in LTS treatment, whereas total mortality (100%) was observed in SCC treatments in dilution higher than 50% of water and sediment. For SCC, median lethal concentration and the 95% confidence limits was 18.30% (14.71-22.77) at 24 h; lowest-observed and no-observed effect concentrations were 12.5% and 6.25%, respectively. Oxidative stress and neurotoxicity were observed in tadpoles exposed to 25% SCC dilution treatment. In addition, there was a large genotoxic effect (micronuclei test) in all sublethal SCC dilution treatments (6.25%, 12.5%, and 25%). These results alert about the high environmental quality deterioration and high ecotoxicity for aquatic fauna of aquatic ecosystems affected by agro-industrial wastewater. PRACTITIONER POINTS: Great mortality of turtles was observed in a basin with a high load of agro-industrial wastewater. San Carlos Channel (SCC), where effluents are spilled, is environmentally deteriorated. The water-sediment matrix of SCC caused 100% lethality in tadpoles. SCC dilutions caused neurotoxicity, oxidative stress, and genotoxicity on tadpoles.

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American Bullfrogs, Aquarana catesbeiana, are invasive anuran species distributed worldwide. One of the adverse impacts that this species causes in native communities is as a reservoir host for pathogens and parasites. Here, we report the coinfection of two pathogenic organisms in A. catesbeiana: Ranavirus and the nematode Eustrongylides. Bullfrogs were collected in the wild in a pond close to the urban area of São Paulo, Brazil. The prevalence of both pathogens was high: 77% were infected with ranavirus with a mean viral load of 1010.3 viral copies, and 100% of the bullfrogs were infected by Eustrongylides sp. with a mean intensity of infection of 13.4 specimens per host. Four host specimens (31%) presented pathological signs that seemed to be related to the Eustrongylides sp. infection, such as internal organs adhered to each other due to high intensity and large size of the nematodes, ulcers, and raw flesh wounds caused by the nematode. The pathogenic and concomitant infections have potential zoonotic implications and raise concerns about human infection risks for Eustrongylides infection. Moreover, such infections may represent an additional level of threat to native communities through the potential shifts in patterns of parasite and pathogen transmission. Future research involving the native anuran community is essential to ascertain whether invasive bullfrogs are attenuating or exacerbating diseases such as ranavirosis and eustrongylidiosis.

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In anurans, the vertebral column diverges widely from that of other tetrapods; yet the molecular mechanisms underlying its morphogenesis remain largely unexplored. In this study, we investigate the role of the homeologous uncx.L and uncx.S genes in the vertebral column morphogenesis of the allotetraploid frog Xenopus laevis. We initiated our study by cloning the uncx orthologous genes in the anuran Xenopus and determining their spatial expression patterns using in situ hybridization. Additionally, we employed gain-of-function and loss-of-function approaches through dexamethasone-inducible uncx constructs and antisense morpholino oligonucleotides, respectively. Comparative analysis of the messenger RNA sequences of homeologous uncx genes revealed that the uncx.L variant lacks the eh1-like repressor domain. Our spatial expression analysis indicated that in the presomitic mesoderm and somites, the transcripts of uncx.L and uncx.S are located in overlapping domains. Alterations in the function of uncx genes significantly impact the development and differentiation of the sclerotome and myotome, resulting in axial skeleton malformations. Our findings suggest a scenario where the homeologous genes uncx.L and uncx.S exhibit antagonistic functions during somitogenesis. Specifically, uncx.S appears to be crucial for sclerotome development and differentiation, while uncx.L primarily influences myotome development. Postallotetraploidization, the uncx.L gene in X. laevis evolved to lose its eh1-like repressor domain, transforming into a "native dominant negative" variant that potentially competes with uncx.S for the same target genes. Finally, the histological analysis revealed that uncx.S expression is necessary for the correct formation of pedicles and neural arch of the vertebrae, and uncx.L is required for trunk muscle development.

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Introduction: The frequent use of pesticides is currently considered a cause of environmental pollution due to the high rate of entry of these substances into agroecosystems. This constitutes a risk for the species that inhabit these ecosystems, in particular anurans whose characteristics make them prone to exposure to and interaction with environmental pollutants. Objective: To report the occurrence of abnormalities in larvae of the common toad Rhinella arenarum inhabiting ponds surrounded by agroecosystems. Methods: In two consecutive springs (2015 and 2016), reproductive events of common toads were monitored in temporary pond systems in agricultural and non-agricultural areas, located near the city of La Plata (Buenos Aires, Argentina). The physicochemical parameters of the ponds were measured, and the stage of each reproductive event was recorded, such as the numbers of adult toads, amplexus and clutches. In the laboratory, the larvae were measured and photographed, their stage of development was recorded, and their morphology was examined under a stereomicroscope. Representative samples (normal and abnormal) from each pond studied were processed for histopathological analysis. Results: In the field studies carried out on a population of R. arenarum collected in an agroecosystem, a lower number of reproductive adults and clutches were observed in relation to the population of a non-agricultural pond. A total of 1 910 larvae were collected: 529 and 1 381 larvae from ponds located in non-agricultural and agricultural areas, respectively. Larvae from the agroecosystem showed two types of abnormalities: severe tail flexure and abdominal bloating. In addition, five degrees of severity could be determined in relation to abdominal bloating. Conclusions: This work reports the high frequency and severity of abnormalities observed in the early stages of R. arenarum larvae living within an agroecosystem, providing evidence of the negative impact that agricultural activities cause on aquatic ecosystems surrounded by farming areas.

Introducción: El uso frecuente de plaguicidas es considerado actualmente una causa de contaminación ambiental debido a las altas tasas de ingreso de estas sustancias a los agroecosistemas. Esta situación es un riesgo para las especies que habitan en estos ecosistemas, en particular los anuros cuyas características los hacen propensos a la exposición e interacción con contaminantes ambientales. Objetivo: Informar la presencia de anormalidades en larvas del sapo común Rhinella arenarum que habitan en estanques rodeados por un agroecosistema. Métodos: En dos primaveras consecutivas (2015 y 2016), se monitorearon los eventos reproductivos del sapo común proveniente de sistemas de estanques temporales ubicados en zonas agrícolas y no agrícolas, cerca de la ciudad de La Plata (Buenos Aires, Argentina). Se midieron los parámetros fisicoquímicos de los estanques y se registraron las etapas de cada evento reproductivo como el número de sapos adultos, amplexos y nidadas. En el laboratorio, las larvas fueron medidas y fotografiadas, se registró su estado de desarrollo y se examinó la morfología de cada una bajo microscopio estereoscópico. Se procesaron muestras representativas (normales y anormales) de cada estanque estudiado para análisis histopatológico. Resultados: En la población de R. arenarum que vive dentro de un agroecosistema, se observó un menor número de adultos reproductores y puestas en relación con la del estanque en la zona no agrícola. Se recolectaron un total de 1 910 larvas: 529 y 1 381 larvas de estanques ubicados en zonas no agrícolas y agrícolas, respectivamente. Las larvas del agroecosistema mostraron dos tipos de anormalidades: severa flexión de la cola y distensión abdominal. Además, se pudo determinar cinco grados de gravedad en relación con la distensión abdominal. Conclusiones: Una alta frecuencia y severidad de anormalidades en los estadios tempranos de larvas de R. arenarum que viven dentro de un agroecosistema proporciona evidencia del impacto negativo que las actividades agrícolas causan en los ecosistemas acuáticos rodeados por áreas de cultivo.

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Background: The development of anthropogenic activities has generated a decline in aquatic fauna populations, and amphibians have been the most affected. The decline of batrachofauna is concerning, as 41% of all species worldwide are endangered. For this reason, rapid, efficient, and non-invasive biodiversity monitoring techniques are needed, and environmental DNA (eDNA) is one such tool that has been sparsely applied in Ecuador. This technique has allowed scientists generates information on species diversity and amphibian community composition from a water sample. This study applied eDNA-based biomonitoring analyses and visual encounter surveys (VES) as inventory techniques to identify the diversity of aquatic amphibians in the Tena River micro-basin (TRMB). Methods: The experimental design was divided into three components: (1) fieldwork: all amphibians were recorded by the VES technique and water samples were collected; (2) laboratory work: DNA isolation from amphibian tissue samples and eDNA-containing filters, amplification, electrophoresis, and sequencing were performed; (3) Data analysis: a local DNA reference database was constructed, and eDNA sequence data were processed for classification, taxonomic assignment, and ecological interpretation. Results: Using both eDNA and VES, we detected 33 amphibian species (13 with eDNA only, five with VES only, and 15 with both methods). These species belonged to six amphibian families: Hylidae being the richest with 14 species (three eDNA, one VES, and 10 with both methods), followed by Strabomantidae with nine species (six eDNA, one VES, and two with both methods). All families were detected with both methods, except for the Aromobatidae, having one single record (Allobates aff. insperatus) by VES. Individually, eDNA detected 28 species and had a detection probability (DP) of 0.42 CI [0.40-0.45], while VES recorded 20 species with a DP of 0.17 CI [0.14-0.20]. Similarly, using VES, Cochranella resplendens was detected for the first time in TRMB, while with eDNA, four mountain frogs Pristimantis acerus, Pristimantis eriphus, Pristimantis mallii, and Pristimantis sp. (INABIO 15591) previously recorded at 1,518 m.a.s.l. at altitudes below 600 m.a.s.l. were detected. Conclusions: Results obtained in this study showed that eDNA-based detection had a greater capacity to detect amphibians in aquatic environments compared to VES. The combination of VES and eDNA improves the sensitivity of species detection and provides more reliable, robust, and detailed information. The latter is essential for developing conservation strategies in the Ecuadorian Amazon.

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Chlorpyrifos (CPF) is one of the most widely used insecticides worldwide despite the fact that many authors have warned about its effects in non-target biota. The effects of CPF on anurans are well known, but the process of recovery from these effects after exposure is less explored. The aim of this study was to evaluate the duration of sublethal effects induced by environmental concentrations of CPF on Ceratophrys ornata tadpoles after exposure. The experimental design consisted of an exposure phase (96 h) in which tadpoles were individually exposed to three concentrations of CPF (0, 0.01 and 0.02 mg CPF/L) and a post-exposure phase (72 h) in which exposed tadpoles were transferred to CPF-free media. Individuals that survived the exposure phase to CPF showed neither long-term lethal effects nor long-term swimming alterations and altered prey consumption after being transferred to CPF-free media. No morphological abnormalities were observed either. However, at the end of both phases, tadpoles emitted shorter sounds with a higher dominant frequency than the tadpoles in the control group, i.e., the tadpoles did not recover their normal sounds. Thus, for the first time in this species, we have shown that effects on sounds should be prioritized as biomarkers of exposure, as they not only provide longer detection times after cessation of exposure, but also involve non-destructive methods. The following order of priority could be established for the selection of biomarkers that diagnose the health status of individuals and precede irreversible responses such as mortality: alterations in sounds > swimming alterations > prey consumption.

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The gastrointestinal tract (GIT) is colonized by resident microbiota but contact with foreign microbiota during feeding can impair GIT functions. During meal digestion, several vertebrates modulate the systemic immune function and immunoregulatory hormones concentration. However, in ectothermic animals, it is not known if this hormonal and immune modulation during the postprandial period is affected by the presence of pathogenic microbiota in the food. This study aimed to investigate the effects of contaminated meal ingestion on hormonal and innate immune responses in bullfrogs (Lithobates catesbeianus). Bullfrogs were divided into three treatments: fed three times with sterilized fish feed (control group), fed twice with sterilized fish feed and once with fish feed containing live bacteria (Aeromonas hydrophila, 109 UFC/mL), and fed three times with fish feed containing live bacteria. Blood and GIT tissues were collected 24 h after treatments to measure plasma and tissue corticosterone levels, NL ratio, and plasma bacterial killing ability. The ingestion of contaminated meal did not affect the hormonal and immune parameters. In conclusion, ingestion of contaminated food was not capable of intensifying the hypothalamic-pituitary-interrenal axis activation and the consequent hormonal and immune responses observed after feeding in bullfrogs. However, our results suggest that the ingestion of three contaminated meals tended to decrease stomach corticosterone levels (nonstatistically significant), possibly contributing to preventing the transmigration of the bacteria to organs outside the GIT.

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It has been suggested that anuran amphibian parasites can cause clinical signs in situations of environmental imbalance. In the family Leptodactylidae, information about hematology is scarce, although these are well-known tools for the diagnosis and prognosis in clinical practice and potential bioindicators of environmental stress. The objective of this study is to describe Leptodactylus luctator hematology, to report the occurrence of hemoparasites and thrombidiform mites, and to compare the hematological variables under the presence and absence of these organisms. Ectoparasites and heparinized blood samples from 40 free-living specimens of L. luctator were collected for analysis. Hematologic variables and total plasma protein were compared between groups with and without hemoparasites and intradermal mites. As results, structures compatible with hemogregarines, Lankesterella sp., five morphotypes of Trypanosoma spp., microfilaria, Aegyptianella sp., an unidentified intraleukocytic hemoparasite, and frog erythrocytic virus (FEV) inclusion bodies were identified in the blood samples, besides Hannemania spp. intradermal mites. The hemoparasite occurrence was higher than previously reported in other anuran families and locations. Also, L. luctator has smaller red blood cells (RBCs) and white blood cells (WBCs), and a hyposegmentation of the neutrophil nucleus, when compared to many other amphibians. White blood cell, neutrophil, and monocyte counts were higher in animals parasitized by mites. There was no correlation between the number of parasitized RBCs and hematologic variables. This study provides anuran hematologic information, in addition to indicating a host reaction to infestation by Hannemania spp. mites, besides constituting the first record of the distribution of hemoparasites and intradermal mites in L. luctator of the study region.

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Melanophryniscus admirabilis is a small toad, critically endangered with a microendemic distribution in the Atlantic Forest in southern Brazil. The amphibian skin microbiome is considered one of the first lines of defense against pathogenic infections, such as Batrachochytrium dendrobatidis (Bd). The knowledge of skin amphibian microbiomes is important to numerous fields, including species conservation, detection, and quantification of environmental changes and stressors. In the present study, we investigated, for the first time, cultivable bacteria in the skin of wild M. admirabilis, and detected Bd fungus by nested polymerase chain reaction (PCR) technique. Skin swab samples were collected from 15 wild M. admirabilis, and the isolation of bacteria was performed by means of different culture strategies. A total of 62 bacterial isolates being Bacillus (n = 22; 34.48%), Citrobacter (n = 10; 16.13%), and Serratia (n = 12; 19.35%) were more frequently isolated genera. Interestingly, all skin samples tested were Bd negative. Some bacterial genera identified in our study might be acting in a synergic relationship and protecting them against the Bd fungus. In addition, these bacteria may play an essential role in maintaining this species in an environment modulated by anthropic actions. This first report of skin cultivable bacteria from M. admirabilis natural population improves our knowledge of skin amphibian microbiomes, contributing to a better understanding of their ecology and how this species has survived in an environment modulated by anthropic action.

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Faunal inventories contribute to our understanding of regional diversity, and are fundamental for policy and de-cision-making regarding the management and conservation of large natural areas. This study aimed to inventory and com-pile information on amphibian species occurring in the North Pantanal region, in the municipal limits of Cáceres, Mato Grosso, Brazil. We used three methods to inventory amphibian species: (1) fieldwork, (2) analysis of specimens deposited in scientif-ic collections, and (3) literature reviews. We registered 49 amphibian species in Cáceres. Of them, 48 species belonged to the Anura order and were distributed across eight families and 20 genera, and one species belonged to the Gymnophiona order (Siphonops paulensis). The families Leptodactylidae (20 spp.) and Hylidae (17 spp.) were dominant in terms of richness, ac-counting for 75.5% of all species found in Cáceres. The remaining families had between four and one species each. The mu-nicipality is strongly influenced by non-forested formations (e.g., the Cerrado and Pantanal) and presents a high species rich-ness for a non-forested location in Brazil. Our findings highlight Cáceres as one of the richest areas in amphibian species in the North Pantanal region, expanding our knowledge regarding frog diversity. This study provides a foundation for future conser-vation strategies and additional assessments of amphibian species in light of potential population declines and other emerg-ing threats.(AU)

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Indivíduos da família Bufonidae são comumente associados a casos de intoxicação de cães após contato com o veneno secretado nas glândulas presentes no tegumento, reforçando a importância de tratamentos efetivos após esta interação. Neste trabalho apresentamos uma revisão sobre casos de intoxicação de cães por venenos de anuros, relacionando os principais sintomas nos cães e os protocolos clínicos utilizados. Realizamos uma busca por artigos que relatem casos de intoxicação de cães por anuros nos repositórios Google Scholar, Scielo e PubMed. Utilizamos palavras-chave nos idiomas português e inglês. Um total de 430 artigos foram encontrados, sendo apenas 17 de acordo com a proposta da pesquisa. Os registros encontrados foram para o Brasil, Austrália e Estados Unidos. As espécies de anuros reportadas na literatura foram exclusivamente as do gênero Rhinella. O maior número dos casos registrados no Brasil ocorreu em ambiente urbano. Os principais sintomas descritos após intoxicação de cães foram salivação em excesso, convulsão e vômito. Óbitos também foram encontrados durante a busca. Principais protocolos para o tratamento após envenenamento foram lavagem da cavidade oral do cão, e administração de atropina, diazepam e fluidoterapia. Foi observado que há influência do tamanho dos cães na severidade após intoxicação, sendo os de pequeno porte mais suscetíveis a quadros letais. Sugerimos, por conta do baixo número de registros, que possivelmente a quantidade de casos acerca desta temática seja subestimado. Neste estudo evidenciamos que os protocolos utilizados para o cuidado dos cães intoxicados não são realizados de forma padrão, alterando de acordo com o quadro clínico apresentado.

Individuals of the Bufonidae family are commonly associated with cases of poisoning in dogs after contact with the venom secreted in glands present in the tegument, reinforcing the importance of effective treatments after this interaction. In this paper, we present a review of cases of poisoning in dogs by anuran venom, relating the main symptoms in dogs and the clinical protocols used. We performed a search for articles reporting cases of anuran poisoning in dogs in the Google Scholar, Scielo, and PubMed repositories. We used keywords in Portuguese and English. A total of 430 articles were found and only 17 of which were in accordance with the research proposal. The records found were for Brazil, Australia, and the United States. The species of anurans reported in the literature were exclusively those of the genus Rhinella. The greatest number of cases registered in Brazil occurred in an urban environment. The main symptoms described after intoxication in dogs were excessive salivation, convulsion, and vomiting. Deaths were also found during the search. The main protocols for treatment after poisoning were washing the dog's oral cavity, and administration of atropine, diazepam, and fluid therapy. It was observed that the size of the dogs influences the severity after intoxication, with small dogs being more susceptible to lethal conditions. Due to the low number of records, we suggest that the number of cases on this topic is possibly underestimated. In this study, we showed that the protocols used for the care of intoxicated dogs are not performed in a standard way, changing according to the clinical picture presented.

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Indirect development is widespread in anurans and is considered an ancestral condition. The metamorphosis of larvae into juveniles involves highly coordinated morphological, physiological, biochemical, and behavioral changes, promoted by the thyroid hormone and interrenal corticosteroids. Stress response to environmental changes is also mediated by corticosteroids, affecting the timing and rate of metamorphosis and leading to great developmental plasticity in tadpoles. Given the potential effect of interrenal gland ontogeny alterations on metamorphosis and the lack of studies addressing both the morphology and endocrinology of this gland in tadpoles, we present corticosterone (CORT) production and histological changes through the ontogeny of interrenal gland in the generalized pond-type tadpole of Rhinella arenarum (Anura, Bufonidae). This species shows the highest concentration of whole-body CORT by the early climax when drastic metamorphic changes begin. This is coincident with the morphological differentiation of steroidogenic cells and the formation of interrenal cords. By this stage, steroidogenic cells have a shrunken cytoplasm, with a significantly higher nucleus-to-cell diameter ratio. The lowest CORT concentration during premetamorphosis and late climax is associated with small undifferentiated cells with lipid inclusions surrounding large blood vessels between kidneys, and with cords of differentiated steroidogenic cells with a significantly lower nucleus-to-cell diameter ratio, respectively. Our study characterizes the morphological and physiological pattern of interrenal gland development, showing an association between certain histological and morphometric characteristics and CORT levels. Variations in this morpho-physiological pattern should be considered when studying the phenotypic plasticity or variable growth rates of tadpoles.

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In amphibians, intra- or interspecific chemical cues are an important source of information about possible predation risk. In anuran tadpoles, this information causes changes at different levels including behavior, morphology, and growth and development. It has been shown that chemical alarm cues trigger antipredator behaviors, such as decreased exploratory activity, in a wide variety of anuran species; however, the cellular origin of the chemical cues has not yet been confirmed by new evidence. Previous works have suggested that the alarm cues originate from a particular cell type in the skin in tadpoles of the family Bufonidae: the epidermal giant cells (GCs). Here, we confirm the presence of GCs in the epidermis of Rhinella arenarum larvae from developmental stages as early as G22, when free-swimming larvae show gregarious behavior. In addition, larval skin homogenates trigger antipredator behaviors in conspecifics from stage G22 onwards, but not at early stages (G19 and G21). This fact exposes experimental evidence for the coexistence between the appearance of GCs and the production of chemical alarm cues during the development of R. arenarum. Furthermore, the antipredator behavioral response of R. arenarum larvae triggered by skin preparations of other species that belong to the same family who also exhibit GCs allows us to speculate that chemical cues appear to be conserved among phylogenetically related species, allowing them to cross-respond to heterospecific cues. Our experimental approaches support the role of GCs as the source of alarm cues in anuran larvae of the family Bufonidae.

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The heart begins to form early during vertebrate development and is the first functional organ of the embryo. This study aimed to describe and compare the heart development in three Neotropical anuran species, Physalaemus albonotatus, Elachistocleis bicolor, and Scinax nasicus. Different Gosner Stages (GS) of embryos (GS 18-20) and premetamorphic (GS 21-25), prometamorphic (GS 26-41), and metamorphic (GS 42-46) tadpoles were analyzed using stereoscopic microscopy and Scanning Electronic Microscopy. Heart development was similar in the three analyzed species; however, some heterochronic events were identified between P. albonotatus and S. nasicus compared to E. bicolor. In addition, different patterns of melanophores arrangement were observed. During the embryonic and metamorphic periods, the main morphogenetic events occur: formation of the heart tube, regionalization of the heart compartments, development of spiral valve, onset of heartbeat, looping, and final displacement of the atrium and its complete septation. Both periods are critical for the normal morphogenesis and the correct functioning of the anuran heart. These results are useful to characterize the normal anuran heart morphology and to identify possible abnormalities caused by exposure to environmental contaminants.

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The ability to learn in the context of predation allows prey to respond to threats by adjusting their behavior based on specific information acquired from their current environment. Habituation is a process that allows animals to adapt to environmental changes. Very little is known about habituation in wild animals in general and there are no studies on habituation in anuran tadpoles in particular. Here, we performed three experiments to investigate the behavioral response of predator naïve Pleurodema thaul tadpoles to repeated stimulation with two predation risk cues (injured conspecific and predator fed cues) which a priori provide different information regarding risk. Experiment 1 showed that P. thaul tadpoles habituate the antipredator response when undergo predation risk chemical cues from injured conspecific and that response is long term. Experiment 2 showed that P. thaul tadpoles did not habituate their antipredator response when exposed to cues derived from an event of nymph odonate preying on P. thaul tadpoles (predator fed cues). Experiment 3 specifically evaluated the risk imposed by each of the risk cues used in Experiment 1 and Experiment 2 and showed that the degree of perceived risk in tadpoles appear to be similar in a single experience with any risk stimuli. We suggest that the behavioral habituation of tadpoles in the context of predation could be modulated by the level of uncertainty associated with risk stimuli.

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Mammals show immune up-regulation and increased plasma and local (gastrointestinal tract) concentrations of some immunoregulatory hormones, such as corticosterone and melatonin, after feeding. However, little is known about the endocrine and immune modulation in the postprandial period of ectothermic animals. This study investigated the effects of feeding on endocrine and immune responses in the bullfrog (Lithobates catesbeianus). Frogs were fasted for 10 days and divided into two groups: fasted and fed with fish feed (5% of body mass). Blood and gastrointestinal tract tissues (stomach and intestine) were collected at 6, 24, 48, 96 and 168 h to measure neutrophil/lymphocyte ratio, plasma bacterial killing ability, phagocytosis of blood leukocytes, plasma corticosterone and melatonin, and stomach and intestine melatonin. Feeding increased plasma corticosterone at 24 h and decreased it at 168 h, and increased neutrophil/lymphocyte ratio at 6, 24 and 96 h. We also observed decreased bacterial killing ability 48 h after feeding. Stomach melatonin increased after 17 days of fasting. We show that feeding activates the hypothalamic-pituitary-interrenal axis and promotes transient immunosuppression, without stimulating an inflammatory response. Increased corticosterone may mobilize energy to support digestive processes and melatonin may protect the stomach during fasting. We conclude that feeding modulates secretion of immunoregulatory hormones, initially increasing plasma corticosterone levels, followed by a decrease at the end of meal digestion, and causes systemic immune cell redistribution, increasing neutrophil/lymphocyte ratio for almost the entire period of meal digestion in bullfrogs. Also, fasting modulates secretion of melatonin in the stomach.

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A list of amphibian and reptile species that occur in open and forested areas of the Atlantic Forest in the municipality of Cruz das Almas, in the Recôncavo Baiano, eastern Brazil is presented. Field sampling occurred between January 2015 to March 2019, totalling 117 samples distributed in three areas: Parque Florestal Mata de Cazuzinha, Mata da Cascalheira, and Riacho do Machado. A total of 1,848 individuals of 69 species (31 anurans, 14 lizards, 19 snakes, two amphisbaenians, and three testudines) was recorded. Additionally, one individual of Ophiodesstriatus was found in Mata da Cascalheira after the end of sampling, totalling 15 lizard species and 70 herpetofaunal species. The prevalence of open-area species and the presence of Phyllopezuslutzae, Diploglossuslessonae, and Dryadosauranordestina in interior forest patches are discussed. Additionally, a new record of the invasive terrapin Trachemysdorbigni in the State of Bahia is reported.

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The Amphibia are considered the most threatened vertebrate class globally, yet in Brazil they are also one of the more diverse and species rich groups. Although, in recent years there has been strong focus on amphibian related research, their parasites have not received the same attention. In Brazil, only a single species of Hepatozoon, namely H. leptodactyli (Lesage, 1908) Pessoa, 1970, has been described from anuran hosts. The present study aimed to describe three new species of Hepatozoon parasitising Leptodactylus labyrinthicus and Leptodactylus latrans from Mato Grosso State, Brazil. From 66 anurans screened for haemogregarines, four belonging to the Leptodactylidae were found positive for species of Hepatozoon. Based on the morphological analysis of peripheral blood gamonts and spleen and liver tissue meronts, three different morphotypes of Hepatozoon spp. were identified. Morphotype 1 (M1) and morphotype 2 (M2) in L. labyrinthicus and morphotype 3 (M3) in L. latrans. Molecular data based on partial 18S rDNA sequences revealed an interspecific divergence, between the species ranging from 0.43% to 1.16%. Phylogenetic analysis recovered isolates from the present study monophyletic with other isolates from Brazilian reptile and anuran hosts, sister to a clade comprising species isolated from African, North American and European reptile and anuran host species. Thus, using morphological and molecular analysis three new species infecting Brazilian Leptodactylidae anurans were identified and described. This study increases the knowledge of Brazilian anurans blood parasites and demonstrates the importance of using integrative approaches for diagnosis of hemoparasites.

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Rhinella icterica is a Brazilian toad with a parotoid secretion that is toxic to insects. In this work, we examined the entomotoxicity of this secretion in locust (Locusta migratoria) semi-isolated heart and oviduct preparations in vitro. The parotoid secretion caused negative chronotropism in semi-isolated heart preparations (at the highest dose tested: 500 µg) and markedly enhanced the amplitude of spontaneous contractions and tonus of oviduct muscle (0.001-100 µg). In addition, the secretion enhanced neurally-evoked contractions of oviduct muscle, which was more sensitive to low concentrations of secretion than the semi-isolated heart. The highest dose of secretion (100 µg) caused neuromuscular blockade. In zero calcium-high magnesium saline, the secretion still enhanced muscle tonus, suggesting the release of intracellular calcium to stimulate contraction. Reverse-phase HPLC of the secretion yielded eight fractions, of which only fractions 4 and 5 affected oviduct muscle tonus and neurally-evoked contractions. No phospholipase A2 activity was detected in the secretion or its chromatographic fractions. The analysis of fractions 4 and 5 by LC-DAD-MS/MS revealed the following chemical compounds: suberoyl arginine, hellebrigenin, hellebrigenin 3-suberoyl arginine ester, marinobufagin 3-pimeloyl arginine ester, telocinobufagin 3-suberoyl arginine ester, marinobufagin 3-suberoyl arginine ester, bufalin 3-adipoyl arginine, marinobufagin, bufotalinin, and bufalitoxin. These findings indicate that R. icterica parotoid secretion is active in both of the preparations examined, with the activity in oviduct possibly being mediated by bufadienolides.

Assuntos