Effect of soil disturbance by agricultural activities on the life history traits of monkey frog (Pithecopus azureus).

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

Abundance, diversity and community characterization of aquatic Coleoptera in a rice field of Northeastern Argentina.

Rice fields occupy large areas in Northeastern Argentina, and in Corrientes this widespead activity has become a feature in the landscape, as it is one of the main producing provinces. The aquatic Coleoptera is part of the fauna inhabiting these artificial environments but little is known about this group in irrigated rice fields. The aims of this study were to determine the diversity and species richness of coleopterans in a typical rice field, and to characterize the community of water beetles through different abundance models. For this, samples were collected from an active rice field located in "El Sombrero" town, in Corrientes Province, between November 2011 and April 2012. An entomological net of 30 cm diameter was used, and species richness, diversity and equitability were calculated monthly; besides, the community composition was characterized by means of rank-abundance models. A total of 74 species of aquatic coleopterans were identified. January and February resulted the months with the highest diversity. The aquatic Coleoptera species found in most of the sampled months were adjusted to the logarithmic rank-abundance model. The data suggests that, if it is properly managed, rice cropping in Northeastern Argentina can support a diverse aquatic coleopteran fauna.

Abundance, diversity and community characterization of aquatic Coleóptera in a rice field of Northeastern Argentina / Abundancia, diversidad y caracterización de la comunidad de coleópteros acuáticos en una plantación de arroz al noreste de Argentina

Rice fields occupy large areas in Northeastern Argentina, and in Corrientes this widespead activity has become a feature in the landscape, as it is one of the main producing provinces. The aquatic Coleoptera is part of the fauna inhabiting these artificial environments but little is known about this group in irrigated rice fields. The aims of this study were to determine the diversity and species richness of coleopterans in a typical rice field, and to characterize the community of water beetles through different abundance models. For this, samples were collected from an active rice field located in "El Sombrero" town, in Corrientes Province, between November 2011 and April 2012. An entomological net of 30 cm diameter was used, and species richness, diversity and equitability were calculated monthly; besides, the community composition was characterized by means of rank-abundance models. A total of 74 species of aquatic coleopterans were identified. January and February resulted the months with the highest diversity. The aquatic Coleoptera species found in most of the sampled months were adjusted to the logarithmic rank-abundance model. The data suggests that, if it is properly managed, rice cropping in Northeastern Argentina can support a diverse aquatic coleopteran fauna.

Las plantaciones de arroz ocupan grandes áreas en el NE argentino. Corrientes es una de las principales provincias productoras de este cereal y al ser un cultivo extensivo ocupa grandes áreas, las cuales pasan a ser una parte característica del paisaje. Los coleópteros acuáticos forman parte de la fauna que habita en estos ambientes artificiales y poco se sabe de la fauna que habita en ellos. Los objetivos de este estudio fueron determinar la diversidad y la riqueza de especies de coleópteros en un campo típico de arroz, y caracterizar la comunidad de escarabajos de agua a través de los diferentes modelos de abundancia. Para ello, se realizaron muestreos con una red entomológica de 30 cm de diámetro en un campo de arroz ubicada en la localidad "El Sombrero", en la provincia de Corrientes. Las muestras fueron recolectadas entre noviembre 2011 y abril 2012. La riqueza de especies, diversidad y equitatividad para todos los meses muestreados fueron calculadas. La composición de la comunidad se caracterizó por medio de modelos de ranking-abundancia. Se identificaron 74 especies de coleópteros acuáticos. Enero y febrero fueron los meses con mayor diversidad. Las especies de coleópteros acuáticos que se registraron en la mayoría de los meses muestreados se ajustaron al modelo logarítmico. Los datos sugieren que, si se gestiona adecuadamente, los cultivos de arroz en el noreste de Argentina pueden albergar una fauna diversa de coleópteros acuáticos.

Helminth community structure in the Argentinean bufonid Melanophryniscus klappenbachi: importance of habitat use and season.

The goal of this study was to evaluate the relative influence of terrestrial habits, season, and host body size on the species richness and abundance of helminth parasites in the toad Melanophryniscus klappenbachi, for which a greater abundance of nematode parasites was expected. A total of 90 toads were collected in the Chaco Province, Argentina. The helminth community found in infected toads included 17 taxa and was dominated particularly by larval parasites. Contrary to our expectations, nematode species showed lower values of infection parameters. Infected toads harbored a maximum of seven species, and the mean helminth richness was 3.16 ± 1.66 species per infected toads. Season played a significant effect on determining the species richness and abundance of the parasite infracommunity. Similarly, the prevalence of infection of several helminth species (8/47%) varied greatly over time. Host body size was the main factor in determining the infrapopulation structure of helminth parasites. Species richness was significantly and negatively correlated with host body size. Strong associations were observed mainly between larvae of some species. The transmission strategies of parasites suggest that this bufonid acquires infections through direct contact with larval parasites from aquatic and terrestrial habitats and by ingestion of infective larvae. The characteristic of the host tegument, such as the presence of alkaloids, could significantly contribute to the low occurrence of infection by skin-penetrating nematodes. Results also showed that diets and mobility of the host and the local microhabitat conditions play an important role in parasitic infections of toads.

Diversity of amhhibians in rice fields from northeastern Argentina / Diversidad deanffibios en campos de arroz en el noreste de Argentnaa / diversidadE de anfÍbios eM campos de arroz NO nordeste da argentina

The anuran biodiversity and richness of a frog community inhabiting rice fields in northeastern Argentina was surveyed and analyzed. The samples were taken between October 2001 and June 2003. Twenty six species of amphibians were identified in five microhabitats: rice fields per se, ditches and paths, natural vegetation, aquatic vegetation and gullies. The natural vegetation was the most diverse of the microhabitats, while gullies were the poorest in species. The amphibian species of three of the microhabitats adjusted to the logarithmic range-abundance model, one to the geometric and one to the broken stick model. The data suggest that rice cropping in northeastern Argentina, if properly managed, can support a diverse anuran fauna.

Se registró y analizó la diversidad y riqueza de una comunidad de anfibios que habita campos de arroz en el nordeste de Argentina. Las muestras fueron obtenidas en el período comprendido entre octubre 2001 y junio 2003. Se identificaron 26 especies habitando cinco microhábitats: campos de arroz, zanjas y caminos, vegetación natural, vegetación acuática y barrancas. La vegetación natural fue el microhábitat más diverso mientras que las barrancas presentaron la menor cantidad de especies. El modelo de rango abundancia serie logarítmica fue el de mejor ajuste para tres de los microhábitats analizados, otro se ajustó al modelo geométrico y el restante al modelo de varilla rota. Los datos sugieren que los cultivos de arroz del nordeste argentino, podrían albergar una fauna muy diversa si están sujetos a un manejo apropiado.

Registrou-se e analisou-se a diversidade e riqueza de uma comunidade de anfíbios que habita campos de arroz no nordeste da Argentina. As amostras foram obtidas no período compreendido entre outubro de 2001 e junho de 2003. Identificaram-se 26 espécies habitando cinco microhábitats: campos de arroz, sulcos e caminhos, vegetação natural, vegetação aquática e barrancas. A vegetação natural foi o microhábitat mais diverso enquanto que as barrancas apresentaram a menor quantidade de espécies. O modelo de espécie-abundância de série logarítmica foi o de melhor ajuste para três dos microhábitats analisados, outro foi ajustou ao modelo geométrico e o último ao modelo de vara quebrada. Os dados sugerem que os cultivos de arroz do nordeste argentino poderiam abrigar uma fauna muito diversa se estão sujeitos a uma manipulação apropriada.

Ticks, Amblyomma rotundatum (Acari: ixodidae), on toads, Chaunus schneideri and Chaunus granulosus (Anura: bufonidae), in northern Argentina.

This communication provides notes on 2 species of toads, Chaunus schneideri and Chaunus granulosus, infested with ixodid ticks, Amblyomma rotundatum, from the provinces of Corrientes and Formosa in northern Argentina. Chaunus schneideri is a new amphibian host record for A. rotundatum, a species previously reported to parasitize other anurans and also reptiles. We examined 74 ticks on 5 toads. All ticks were A. rotundatum; all adults were females, and all developmental stages were randomly attached to host body parts. Ticks remained attached to one of the toads for from 7 to 17 days after the host was captured. One toad, encumbered with 33 ticks, was moribund when found and died shortly thereafter.

Coexistence of helminth species in Lysapsus limellus (Anura: Pseudidae) from an Argentinean subtropical area: influence of biotic and abiotic factors.

The need for studies on helminth communities of South American amphibians was addressed by examining changes in composition and population dynamics of the helminth component and infracommunities in the frog Lysapsus limellus Cope, 1862, from 1994 to 1996. Two pond types were considered, one permanent and one semipermanent. The main goals of this study were (1) to investigate the relationships between pond type, season, study time, frog body size, and frog sex and the presence-absence and counts of helminth parasite species in the frog host, L. limellus, and (2) to examine the co-occurrence of the different parasite species in the frog host in terms of the structure, assembly, and dynamics of the helminth infracommunity. Parasite presence and absence were analyzed using logistic regression and parasite counts were analyzed using log-linear modeling. To examine the association between parasite species, a principal components analysis was carried out on the correlation matrix for the counts. The pattern of co-occurrences was also examined through a randomization test. The main results were as follows: (1) five parasite species were found in the infracommunity; (2) the pond type and the host size class were the principal factors related to the presence and absence of parasites for the three dominant species, while the year of study and the host sex were only important for one of the species; (3) for the parasite counts, many more factors were significant, with body size class and pond type always important factors for the three core species of the infracommunity, with season, year of study, and sex also sometimes important, and (4) strong associations were observed between some helminth species of the host from the permanent pond, but the same species did not co-occur in frogs in the semipermanent pond. The life histories of the five species can be considered as opportunistic or "r strategists."