RESUMO
Studying species interactions in nature often requires elaborated logistics and intense fieldwork. The difficulties in such task might hinder our ability to answer questions on how biotic interactions change with the environment. Fortunately, a workaround to this problem lies within scientific collections. For some animals, the inspection of preserved specimens can reveal the scars of past antagonistic encounters, such as predation attempts. A common defensive behaviour that leaves scars on animals is autotomy, the loss of a body appendage to escape predation. By knowing the collection site of preserved specimens, it is possible to assess the influence of organismal biology and the surrounding environment in the occurrence of autotomy. We gathered data on tail loss for 8189 preserved specimens of 33 snake and 11 amphisbaenian species to investigate biological and environmental correlates of autotomy in reptiles. We applied generalized linear mixed effect models to evaluate whether body size, sex, life-stage, habitat use, activity pattern, biome, tropicality, temperature and precipitation affect the probability of tail loss in limbless reptiles. We observed autotomy in 23.6% of examined specimens, with 18.7% of amphisbaenian and 33.4% of snake specimens showing tail loss. The probability of tail loss did not differ between snakes and amphisbaenians, but it was higher among large-sized specimens, particularly in adults and females. Chance of tail loss was higher for diurnal and arboreal species, and among specimens collected in warmer regions, but it was unaffected by biome, precipitation, and tropicality. Autotomy in limbless reptiles was affected by size-dependent factors that interplay with ontogeny and sexual dimorphism, although size-independent effects of life-stage and sex also shaped behavioural responses to predators. The increase in probability of tail loss with verticality and diurnality suggests a risk-balance mechanism between species habitat use and activity pattern. Although autotomy is more likely in warmer regions, it seems unrelated to seasonal differences in snakes and amphisbaenians activity. Our findings reveal several processes related to predator-prey interactions involving limbless reptiles, demonstrating the importance of scientific collections to unveil ecological mechanisms at different spatio-temporal scales.
Assuntos
Lagartos , Feminino , Animais , Lagartos/fisiologia , Cauda/fisiologia , Comportamento Predatório , Cicatriz , EcossistemaRESUMO
Parasite infections may contingency different aspects of the hosts' lives, and are usually expected to directly or indirectly compromise host reproduction. However, although amphibians have historically been study models in parasite ecology, the effects of parasitism on amphibians' reproduction remain unknown. Thus, we investigated how the parasite load varies as a function of climatic seasonality (rainy and dry season) and intrinsic host characteristics (size and sex), as well as the relationship between parasite load and reproductive investment in males and females of a small frog (Pseudopaludicola pocoto Magalhães, Loebmann, Kokubum, Haddad & Garda, 2014) in the Brazilian semiarid region. The parasitological parameters of the studied population were not influenced by the season of the year or by the hosts' body size, but females of P. pocoto had a higher prevalence and intensity of infection than males. The number of oocytes and the volume of the testes were not related to the parasite load, revealing that the parasitism did not negatively impact the gonadal investment in P. pocoto. Our findings suggest that short-lived species, such as the tiny Pseudopaludicola species, have a high reproductive investment independent of their parasitic interactions. In addition, this should be true mainly in those species that live in seasonally dry environments, such as P. pocoto, in which reproduction is even more constrained by the shortened and unpredictable rainy period.
Como infecções parasitárias podem contigenciar diversos aspectos da vida dos hospedeiros, de modo geral, espera-se que o parasitismo comprometa direta ou indiretamente a reprodução dos hospedeiros. Contudo, apesar dos anfíbios historicamente terem sido modelos de estudos em ecologia parasitária, os efeitos do parasitismo na reprodução de anfíbios permanecem incompreendidos. Neste trabalho investigamos como a carga parasitária varia em função da sazonalidade climática (período chuvoso e seco) e de características intrínsecas dos hospedeiros (tamanho e sexo), bem como a relação entre a intensidade de infecção e o investimento reprodutivo em machos e fêmeas de uma pequena rã (Pseudopaludicola pocoto Magalhães, Loebmann, Kokubum, Haddad & Garda, 2014) no semiárido brasileiro. Os parâmetros parasitológicos da população estudada não foram influenciados pela estação do ano nem pelo tamanho corpóreo dos hospedeiros, mas as fêmeas de P. pocoto apresentaram maior prevalência e intensidade de infecção que os machos. A carga parasitária não foi relacionada com o número de ovócitos nem com o volume dos testículos, revelando que o parasitismo não impactou negativamente o investimento gonadal em P. pocoto. Nossos achados sugerem que espécies com baixa longevidade, como as diminutas espécies de Pseudopaludicola, apresentam um alto investimento reprodutivo independente de suas interações parasitárias. Complementarmente, isto deve ocorrer sobretudo naquelas espécies que vivem em ambientes sazonalmente secos, como P. pocoto, nos quais a reprodução é ainda mais contigenciada pela brevidade e imprevisibilidade do período chuvoso.
Assuntos
Anuros/parasitologia , Reprodução , Carga Parasitária/veterinária , Helmintos/parasitologia , Interações Hospedeiro-Parasita/fisiologia , Estações do AnoRESUMO
This study reports helminth infection patterns of the lizard Tropidurus hispidus from an area of semiarid caatinga in northeastern Brazil (Ceará state). The lizard population was parasitized by 8 helminth species, and the species composition of the component community resembles that found for other Neotropical lizards. The prevalence of parasites was higher for males compared with females, whereas no relation was found between intensity of infection of 2 parasites (Parapharyngodon alvarengai and Physaloptera lutzi) and the lizards body size. For reproductive females, parasite infection intensity was negatively correlated to reproductive investment.
Assuntos
Helmintíase Animal/epidemiologia , Lagartos/parasitologia , Carga Parasitária/veterinária , Animais , Tamanho Corporal , Brasil/epidemiologia , Clima , Tamanho da Ninhada/fisiologia , Feminino , Fertilidade/fisiologia , Helmintíase Animal/parasitologia , Lagartos/fisiologia , Masculino , Prevalência , Reprodução/fisiologia , Fatores SexuaisRESUMO
The choice of sampling methods is a crucial step in every field survey in herpetology. In countries where time and financial support are limited, the choice of the methods is critical. The methods used to sample snakes often lack objective criteria, and the traditional methods have apparently been more important when making the choice. Consequently researches using not-standardized methods are frequently found in the literature. We have compared four commonly used methods for sampling snake assemblages in a semiarid area in Brazil. We compared the efficacy of each method based on the cost-benefit regarding the number of individuals and species captured, time, and financial investment. We found that pitfall traps were the less effective method in all aspects that were evaluated and it was not complementary to the other methods in terms of abundance of species and assemblage structure. We conclude that methods can only be considered complementary if they are standardized to the objectives of the study. The use of pitfall traps in short-term surveys of the snake fauna in areas with shrubby vegetation and stony soil is not recommended.
Assuntos
Biodiversidade , Serpentes/classificação , Animais , Brasil , Análise Custo-Benefício , Clima Desértico , Densidade Demográfica , Estudos de Amostragem , Fatores de TempoRESUMO
We studied a snake assemblage from an area of Caatinga with shrub and tree vegetation to describe the natural history of the snake species. A total of 636 individuals among 22 species from four families were recorded. The distribution of species abundances is log-normal; and the composition presents typical species from the Caatinga, with Oxybelis aeneus (Wagler, 1824) and Philodryas nattereri Steindachner, 1870 being the most common. The natural history of each species is described based on information regarding activity patterns, diet, habitat use, reproduction, and defensive repertoire obtained during the study, as well as on information available in the literature. The study area is located in a priority region for conservation and our results emphasize that conservation policies should be implemented in the region.(au)
Assuntos
Animais , Comportamento Animal , Dieta , Fauna/análise , Serpentes/classificaçãoRESUMO
We studied a snake assemblage from an area of Caatinga with shrub and tree vegetation to describe the natural history of the snake species. A total of 636 individuals among 22 species from four families were recorded. The distribution of species abundances is log-normal; and the composition presents typical species from the Caatinga, with Oxybelis aeneus (Wagler, 1824) and Philodryas nattereri Steindachner, 1870 being the most common. The natural history of each species is described based on information regarding activity patterns, diet, habitat use, reproduction, and defensive repertoire obtained during the study, as well as on information available in the literature. The study area is located in a priority region for conservation and our results emphasize that conservation policies should be implemented in the region.(au)