Genotoxic risk assessment of solar UV radiation in tadpoles from Brazilian wetlands.

Solar ultraviolet (UV) radiation is an environmental genotoxic factor linked to amphibian decline. Here we assessed the genotoxic risk of UVB and UVA exposure for tadpoles from open ponds in southern Brazil, a mid-latitude region influenced by stratospheric ozone depletion. Daily UV doses were measured on the surface of a pond in Taim Ecological Station (TAIM; 32°49'24''S; 52°38'31''W) on a cloudless summer day to predict the worst-case scenario for UV-induced DNA damage. Pond descriptors were related to the use of microhabitats by Boana pulchella tadpoles in two ponds over the climate seasons of 2013 and 2014. Our results indicate that shaded microhabitats were more frequent than unshaded ones in autumn, winter, and spring but not in summer. Hence, the penetration of UV radiation into the water of unshaded microhabitats was evaluated through laboratory experiments with artificial UV sources and pond water samples. Physical and biological sensors were applied in the experiments to measure the incident UV radiation and its genotoxic action. By integrating field and laboratory data, we demonstrate that low doses of biologically effective UV radiation reached the tadpoles in autumn, winter, spring, and early summer due to a high proportion of shaded microhabitats and a high concentration of solids in unshaded microhabitats. However, the relative reduction of shaded microhabitats jointly with a declining water level in late summer may have exposed tadpoles to high UV doses. Our experiments also indicate that solar UVB radiation, but not UVA, is primarily responsible for the induction of DNA pyrimidine dimers in organisms living under the surface of aquatic ecosystems. The present work highlights the determinant role of wetland descriptors for minimizing the genotoxic potential of UV radiation and its consequences for amphibians.

Effects of isolated and combined exposures of Boana curupi (Anura: Hylidae) tadpoles to environmental doses of trichlorfon and ultraviolet radiation.

The biodiversity collapse strongly affects the amphibian group and many factors have been pointed out as catalytic agents. It is estimated that several events in the amphibian population decline worldwide may have been caused by the interaction of multiple drivers. Thus, this study aimed to evaluate the stressful effects of the exposure to environmental doses of trichlorfon (TCF) pesticide (0.5 µg/L; and an additional 100-fold concentration of 50 µg/L) and ultraviolet radiation (UV) (184.0 kJ/m² of UVA and 3.4 kJ/m² of UVB, which correspond to 5% of the daily dose) in tadpoles of the Boana curupi species (Anura: Hylidae). The isolated and combined exposures to TCF happened within 24 h of acute treatments under laboratory-controlled conditions. In the combined treatments, we adopted three different moments (M) of tadpole irradiation from the beginning of the exposures to TCF (0 h - M1; 12 h - M2; and 24 h - M3). Then, we evaluated tadpole survival, change in morphological characters, induction of apoptotic cells, lipid peroxidation (LPO), protein carbonyl content (PCC), glutathione S-transferase (GST), non-protein thiols (NPSH), and acetylcholinesterase (AChE), as well as the induction of genomic DNA (gDNA) damage. UVB treatment alone resulted in high mortality, along with a high level of apoptosis induction. Both UVA, UVB, and TCF increased LPO, PC, and AChE, while decreased GST activity. Regarding co-exposures, the most striking effect was observed in the interaction between UVB and TCF, which surprisingly decreased UVB-induced tadpole mortality, apoptosis, and gDNA damage. These results reinforce the B. curupi sensitivity to solar UVB radiation and indicate a complex response in face of UVB interaction with TCF, which may be related to activation of DNA repair pathways and/or inhibition of apoptosis, decreasing UVB-induced tadpole mortality.

Impact of solar UV radiation on amphibians: focus on genotoxic stress.

Solar UV radiation is one of the most important environmental genotoxic factors. Its incidence increased due to stratospheric ozone depletion, climate changes, and deforestation, and plays a crucial role in the worldwide decline of the populations of amphibians. Even sublethal effects of UV-induced genotoxicity may cause drastic consequences in the performance and fitness of amphibians. We reviewed the existing literature searching for research papers focused on DNA damage (and responses) in various species by environmental relevant UVB and UVA doses. We found twenty one papers relative to this topic, but only four of them concerned direct measurements of DNA lesions in vivo. Finally, we identify knowledge gaps and provide recommendations for future investigations concerning the impact of the genotoxicity induced by sunlight on amphibians.

Hematophagous Flies Attracted to Frog Calls in a Preserved Seasonal Forest of the Austral Neotropics, with a Description of a New Species of Corethrella (Diptera: Corethrellidae).

The signaler-eavesdropper interaction has been investigated for a wide range of organisms, and although many flies feed on calling frogs, this dynamic has been addressed only poorly in the austral Neotropics. We investigated this interaction in southern Brazil using pairs of suction traps (acoustic + silent) broadcasting frog calls or an artificial white noise in ponds and streams. From 139 sessions, flies of the genera Corethrella (Corethrellidae), Forcipomyia (Ceratopogonidae) and Uranotaenia (Culicidae) were collected, including five Corethrella species, the most abundant of which was previously unknown and is formally described here. Additionally, we present the southernmost records of Corethrella lopesi, C. alticola and C. atricornis. Numbers of Forcipomyia midges and Uranotaenia mosquitoes did not differ between silent traps and traps broadcasting frog calls, and did not differ between white noise traps and adjacent silent traps. However, the number of female Corethrella was significantly higher in traps broadcasting calls of the pond-breeding frog P. aff. gracilis compared to adjacent silent traps; calls of this frog attracted the five Corethrella species and also collected significantly more female Corethrella than the white noise. By evaluating different taxa of flies and broadcasting different sounds, we demonstrated that Corethrella midges were attracted only to the acoustic cue of P. aff. gracilis calls, while Forcipomyia and Uranotaenia were captured in traps by chance. Our results suggest that female Corethrella feed on males of the common pond-breeding frog P. aff. gracilis in southern Brazil, and highlight the utility of frog call traps in revealing the diversity of Corethrella in the austral Neotropics.

Pequenos mamiferos nao-voadores (Didelphimorphia, Rodentia) em campos litoraneos do extremo sul do Brasil

Non-volant small mammals are key elements in natural environments due its importance as food resource. This study aimed to investigate the species composition and habitat occupancy by non-volant small mammals (Didelphimorphia, Rodentia) in a coastal grassland area in southern Rio Grande do Sul coastal plain. Between April 2009 and March 2010 pitffal traps were used to capture small mammals in coastal grasslands associated to sand dunes and arbustive Restinga. We sampled 180 individuals including two marsupials (Cryptonanus guahybae and Didelphis albiventris) and seven rodent species (Calomys laucha, Cavia aperea, Ctenomys flamarioni, Deltamys kempi, Oligoryzomys flavescens, Oxymycterus nasutus and Scapteromys tumidus). Cryptonanus guahybae, D. albiventris and C. flamarioni were captured only in dunes while C. aperea and O. nasutus were recorded only in arbustive Restinga habitats. Calomys laucha, D. kempi, O. flavescens and O. nasutus were captured in both habitats. Oligoryzomys flavescens and C. laucha were the most representative species in both habitats, comprising respectively 40.7 and 38.9% of captures in dunes and 56.3 and 34.9% of captures in Restinga habitats. The species richness recorded in the sampled coastal grasslands area was lower than those previously recorded in subtropical forest coastal systems.

Pequenos mamíferos não-voadores são elementos chave em ambientes naturais devido a sua importância como recurso alimentar. Este estudo teve como objetivo investigar a composição de espécies e a ocupação de habitat por pequenos mamíferos não-voadores (Didelphimorphia, Rodentia) em uma área de campos litorâneos na região sul da planície costeira do Rio Grande do Sul. Entre abril de 2009 e março de 2010 armadilhas de interceptação e queda foram utilizadas para a captura de pequenos mamíferos em campos associados a dunas e a restinga arbustiva. Foram amostrados 180 indivíduos pertencentes a duas espécies de marsupiais (Cryptonanus guahybae e Didelphis albiventris) e sete espécies de roedores (Calomys laucha, Cavia aperea, Ctenomys flamarioni, Deltamys kempi, Oligoryzomys flavescens, Oxymycterus nasutus e Scapteromys tumidus). Cryptonanus guahybae, D. albiventris e C. flamarioni foram capturados somente em dunas, enquanto que C. aperea e O. nasutus foram registrados somente em restinga arbustiva. Calomys laucha, D. kempi, O. flavescens e O. nasutus foram capturados em ambos os ambientes. Oligoryzomys flavescens e C. laucha foram as espécies mais representativas em ambos os ambientes, compreendendo respectivamente 40,7 e 38,9% das capturas em dunas, e 56,3 e 34,9% das capturas em restinga. A riqueza de espécies registrada na área de campo litorâneo amostrada foi inferior a aquelas previamente registradas em sistemas florestais costeiros subtropicais.

Does human influence on coastal grasslands habitats affect predation pressure on snakes? / A influência humana afeta a pressão de predação em serpentes em ambientes de campos costeiros?

The loss and modification of habitats by humans have been considered key factors in the decline of diversity of species worldwide. However, the real effect caused by these disturbances on the biota is still poorly understood. The assessment of the changes in the network of interspecific interactions, such as predation rates on the native fauna, can be an important tool to diagnose the functionality of disturbed ecosystems. In this study we evaluate the predation rate on snakes in coastal grasslands in South America under human influence. Predation rate of artificial snakes, unlike that obtained in other studies, was lower in human-altered areas than preserved ones. Our findings may be due to a reduction in the abundance and/or richness of species of native predators in more disturbed areas.

A perda e modificação de habitats por seres humanos têm sido consideradas fatores chave no declínio da diversidade de espécies em todo o mundo. No entanto, o efeito real causado por estes distúrbios sobre a biota ainda é pouco compreendido. A avaliação das mudanças na rede de interações interespecíficas, como as taxas de predação sobre a fauna nativa, pode ser uma importante ferramenta para diagnosticar a funcionalidade dos ecossistemas perturbados. Neste estudo foi avaliada a taxa de predação de serpentes em campos costeiros na América do Sul sob a influência humana. A taxa de predação de serpentes artificiais, ao contrário do que foi observado em outros estudos, foi menor em áreas antropizadas do que em áreas preservadas. Esse resultado pode ser devido a uma redução na abundância e/ou riqueza de espécies de predadores nativos nas áreas perturbadas.

Diversity and habitat use by snakes and lizards in coastal environments of southernmost Brazil / Diversidade e uso do ambiente por serpentes e lagartos em ambientes costeiros do extremo sul brasileiro

This study examined species composition differences among snake and lizard assemblages from coastal dunes and restinga habitats in southernmost Brazil. Animals were collected between April 2009 and March 2010 using pitfall traps, artificial shelters, and time-constrained searches in grasslands areas susceptible to flooding. Species richness was higher in the restinga, but lower than the observed in other Brazilian biomes, possibly associated with more unstable microclimate conditions and low habitat complexity (vertical and horizontal distribution of the vegetation) in this habitat. This hypothesis is supported by the fact that the most abundant species of both snakes and lizards have fossorial habits. The assemblage of snakes is apparently mainly determined by abiotic characteristics of the habitat, while the assemblage of lizards, by vegetation cover.

O estudo teve como objetivo avaliar a composição de espécies de serpentes e lagartos em ambientes costeiros no extremo sul brasileiro. Foram feitas amostragens sistematizadas em hábitats de dunas e restingas entre abril de 2009 e março de 2010 por meio de armadilhas de interceptação e queda, abrigos artificiais e procuras visuais. O ambiente de restinga revelou uma maior riqueza de espécies do que as dunas. As taxocenoses revelaram uma menor riqueza do que a observada em outros biomas brasileiros, o que parece estar associado às condições microclimáticas menos estáveis e à baixa complexidade estrutural desses habitats (distribuição vertical e horizontal da vegetação). Essa hipótese parece ser reforçada pelo fato de tanto para serpentes quanto para lagartos as espécies mais abundantes apresentam hábitos fossoriais. Aparentemente a taxocenose de serpentes é determinada predominantemente pelas características abióticas (microclima) do habitat enquanto que a de lagartos pelo padrão de cobertura vegetal.

Comportamento alimentar aquático de Liophis jaegeri (Günther 1858) (Serpentes, Dipsadidae) em cativeiro / Aquatic feeding behavior of Liophis jaegeri (Günther 1858) (Serpentes, Dipsadidae) in captivity

Os itens que compõem a dieta das espécies são peças fundamentais na definição de sua dimensão de nicho e interferem, em última análise, em processos de estruturação das comunidades. As necessidades relacionadas à alimentação direcionam o modo pelo qual as espécies usam o ambiente. Apesar de se tratar de uma espécie com ampla distribuição geográfica, existem poucos estudos a respeito da biologia geral e do comportamento alimentar de Liophis jaegeri. Os estudos disponíveis indicam se tratar de uma espécie associada à ambientes alagados, porém, a importância de presas aquáticas na dieta desta serpente tem recebido pouca atenção. Em geral os estudos disponíveis sugerem que a presença de presas aquáticas (peixes e girinos) no trato digestivo de indivíduos dissecados seja resultado de ingestões acidentais. No presente estudo, a partir de gravações em vídeo realizadas em cativeiro, apresentamos dados inéditos que revelam a habilidade de L. jaegeri forragear em ambiente aquático, sendo capaz de detectar, subjugar e ingerir de modo eficiente peixes da espécie simpátrica Cheirodon interruptus. Tais informações indicam que a relevância de presas aquáticas na dieta desta serpente possa ser maior do que o até então apresentado pela literatura. Consequentemente, a disponibilidade de corpos d'água e de peixes podem influenciar os padrões de distribuição e abundância de indivíduos desta serpente na natureza.

Dietary composition is an essential component in niche dimension and interferes in the community structuring process. The needs related to feeding behavior drives the way species use their habitats. Despite the wide geographical distribution of Liophis jaegeri, studies concerning its general biology and feeding behavior are very scarce. The available information indicates that L. jaegeri is associated to humid or flooded habits, however the importance of aquatic preys in their diet has not received much attention. In general, the available information suggests that the presence of tadpoles and fishes in the digestive tract of dissected snakes are the result of incidental ingestion. In the present study, we present information on the ability of L. jaegeri to forage in aquatic habitats. Using video recordings made in captivity, we observed that snakes were able to detect, subdue and ingest efficiently the sympatric fish Cheirodon interruptus. These observations suggest that the importance of aquatic preys is higher than previously reported in the literature. Therefore, we believe that the existence of water bodies and the availability of aquatic preys play important roles in the habitat suitability for L. jaegeri snakes.

Playing dead to stay alive: death-feigning in Liolaemus occipitalis (Squamata: Liolaemidae) / Simulando a morte para manter-se vivo: tanatose em Liolaemus occipitalis (Squamata: Liolaemidae)

Predation is the major selective force that drives the development of a series of defense mechanisms by the species. These mechanisms are efficient in that it limits the ability of predators to detect, recognize and subdue their prey. In lizards for example, the tail loss and locomotor escape are the most common defensive behavior reported on the literature. Additionally, in response to external stimuli, some lizards exhibit a peculiar defensive behavior: death-feigning or thanatosis. Here we describe the first record of death-feigning in a population of Liolaemus occipitalis in a coastal sand dune habitat in Southernmost Brazil. A total of 86 individuals were tested. During handling 75.6 percent of lizards feigned death. The duration of this behavior was longer when the observer remained closer to the lizards, suggesting the ability of L. occipitalis to evaluate the predation risk.

A pressão exercida pela predação é a principal força seletiva que direciona o estabelecimento de uma série de mecanismos de defesa por parte das espécies. Esses mecanismos são eficientes na medida em que limitam a capacidade dos predadores em detectar, reconhecer ou subjugar suas presas. Em lagartos, por exemplo, os comportamentos defensivos mais frequentemente citados na literatura são a autotomia caudal e a fuga. Além disso, em resposta a estímulos externos, alguns lagartos podem exibir um comportamento peculiar: fingem-se de mortos (tanatose). Neste estudo descrevemos o primeiro registro de tanatose em uma população de Liolaemus occipitalis em área de dunas costeiras no extremo Sul do Brasil. Um total de 86 indivíduos foram testados. Durante o manuseio, 75,6 por cento dos lagartos exibiram o comportamento de tanatose. A duração deste comportamento foi maior quando o observador permanecia a distâncias mais curtas dos lagartos, sugerindo uma capacidade de L. occipitalis em avaliar o risco de predação.