ABSTRACT Entomofauna associated with decaying cadavers may be useful in criminal investigation, either through the development of immature insects of interest or through entomological succession in corpses. These factors may vary if the insects are exposed to toxic substances that can modify the insect's developmental cycle, as well as its own occurrence, which would imply significant changes in the results of any investigation. However, there are few studies on how contamination by toxic compounds can affect the action of insects on carcasses and their consequence for forensic expertise. Therefore, this study aimed to test the hypothesis that the normal visitation of flies and beetles is altered in insecticide-contaminated carcasses. The experiment was carried out in a sugarcane plantation, using pig carcasses contaminated with insecticide and the same number of carcasses without any type of contamination as a control. In all experiments, the contaminated carcasses reached the final phase of decomposition in a longer time than the uncontaminated carcasses of the control group. A total of 2.767 specimens were collected and identified, 2.103 individuals from the order Diptera and 664 from the order Coleoptera. There was a significant geometric regression adjustment during the decomposition phases only for the control group, different from the contaminated carcasses in which this pattern did not occur. Results show that contamination by insecticide alters decomposition time and phase, altering the action of flies and beetles, affecting the abundance, composition of species as well as their activities, which can alter the data used by experts in criminal experts.

ABSTRACT Corpses in Brazil are commonly hidden in sugarcane plantations in the attempt to delay their finding and hinder the solution of the crime. On the other hand, these plantations are regularly sprayed with insecticides for pest control. Until now no study has reported the effects of insecticides on ant fauna. This study aimed to test the hypothesis that if a body hidden in a monoculture is accidentally contaminated by an insecticide, both the carcass decomposition pattern and the Formicidae fauna will be affected. To accomplish this, pig carcasses contaminated and non-contaminated were placed in a sugarcane monoculture environment and subsequently examined for data collection every 24 hours. The concentration used to contaminate the carcasses was 20 grams per liter of thiamethoxam. The decomposition patterns of contaminated carcasses were changed, in turn affecting the behavior of Formicidae fauna. A total of 5318 ants were collected, 3397 in contaminated carcasses and 1919 in non-contaminated carcasses, and 30 species of 11 genera were identified. According to the analysis, there are no differences between the composition of species between contaminated and non-contaminated carcasses, however, a significant difference was observed in the composition of species along the stages of decomposition between the two types of carcasses. Therefore, our hypothesis has been confirmed, contaminated carcasses undergo changes in their normal pattern of decomposition and the fauna of ants that act on them. As this group of insects has great importance for forensic sciences, the analysis of the experts should take these results into account.

Com o objetivo de descrever alguns aspectos populacionais e reprodutivos de Bryconamericus stramineus em riachos da bacia do rio Guiraí, Alto Rio Paraná, realizamos amostragens bimestrais de Outubro/2006 a Agosto/2007 em sete riachos da bacia. Foram coletados 960 indivíduos, sendo 532 fêmeas, 316 machos e 112 de sexo indeterminado. Constatamos variação significativa na proporção sexual (Χ² = 32,82; p < 0,001). As fêmeas foram maiores (59,7 mm) que os machos (58,9 mm); no entanto, os machos apresentaram maior coeficiente angular de crescimento (b). Estimamos que 50% das fêmeas estão sexualmente maduras com 36,4 mm de comprimento padrão. As maiores frequências de fêmeas com ovários desenvolvidos foram observadas em Outubro, sendo que o único mês em que não foram encontradas fêmeas maduras foi Junho. A fecundidade media foi estimada em 313 ovócitos e a fecundidade relativa foi de 184,6 ovócitos/g. O comprimento assintótico foi estimado em 62,8 mm e a taxa de crescimento em 0,76. O índice de performance de crescimento foi calculado em 3,47, a longevidade em 3,94 anos e a mortalidade em 1,18. O padrão de recrutamento da espécie estudada apresentou picos concentrados no período de menor pluviosidade.

In order to describe some aspects of the population ecology of Bryconamericus stramineus in the Guiraí River basin, upper Paraná River basin, samples were taken bimonthly from October 2006 to August 2007 at seven sites in the basin. A total of 960 individuals, including 532 females, 316 males, and 112 of undetermined sex, were collected. A significant variation in the sex ratio was observed (Χ2 = 32.82; p < 0.001). Females were larger (59.7 mm) than males (58.9 mm); however, males showed a larger angular growth coefficient (b) than females. It was estimated that 50% of females were sexually mature at 36.4 mm. The highest rate of ovary development was observed in October, while in June 2007 no mature females were found. Mean fecundity was estimated at 313 eggs, and the relative fecundity was 184.6 eggs/g. The asymptotic was estimated at 62.8 mm and the growth rate at 0.76. The growth performance index was calculated at 3.47, the longevity at 3.94 years and the mortality (M) at 1.18 years. The recruitment pattern of the species showed peaks concentrated in periods of low rainfall.

O objetivo deste estudo foi caracterizar a dieta das espécies de peixes mais abundantes no córrego Franco (Ivinhema, MS). Os peixes foram capturados mensalmente, no período de março de 2006 a fevereiro de 2007. Para inferência da dieta de espécies que se alimentam de itens macroscópicos, o conteúdo estomacal de cada indivíduo foi retirado, pesado (em g) e posteriormente analisando sob lupa. Os dados obtidos para cada espécie em cada unidade amostral foram analisados a partir dos seguintes métodos: Freqüência de Ocorrência, Índice de Análise Volumétrica e Índice de Importância. Foram coletadas 17 espécies de peixes, na sua grande maioria Characiformes, com dez espécies, duas espécies de Siluriformes, duas de Perciformes, duas de Gymnotiformes e uma de Synbranchiformes. A alimentação das duas espécies estudadas do gênero Astyanax baseou-se principalmente de itens de origem vegetal independentemente da origem; Serrapinnus notomelas alimentou-se de itens vegetais, predominantemente de algas; Hemigrammus marginatus apresentou um hábito alimentar insetívoro principalmente de origem alóctone; Corydoras aeneus e Eigenmannia trilineata alimentaram-se basicamente de insetos aquáticos; sedimento foi o principal item alimentar de Hypostomus ancistroides, seguido por algas e macrófitas; Crenicichla britiskii alimentou-se principalmente de insetos terrestres.

Diet of fish fauna from Franco stream, Mato Grosso do Sul, Brazil. The aim of this study was to characterize the diet of the most abundant fish species in the Franco stream (Ivinhema, MS). Fish were captured monthly, from March 2006 to February 2007. To infer the diet of species that feed on macroscopic items, the stomach contents of each individual was removed, weighed (g) and subsequently analyzed under stereomicroscope. The data obtained for each species in each sampling unit were analyzed with the following methods: Frequency of Occurrence, Volumetric Analysis Index and Index of Importance. We collected 17 species of fish, the vast majority Characiformes, with ten species, two species of Siluriformes, two of Perciformes, two of Gymnotiformes and one of Synbranchiformes. The diet of two species of the genus Astyanax was based mainly on items of plant origin; Serrapinnus notomelas fed up of plant items, mainly from algae; Hemigrammus marginatus showed a mainly insectivorous feeding habits of alien origin, Corydoras aeneus and Eigenmannia trilineata fed up primarily of aquatic insects; sediment was the main food item of Hypostomus ancistroides, followed by algae and macrophytes; Crenicichla britiskii fed mainly on terrestrial insects.

Diversidade de formigas epigéicas (Hymenoptera, Formicidae) em ambientes no Centro-Oeste do Brasil. Foi comparada, através do uso de índices de diversidade e modelos de abundância de espécies, a diversidade das comunidades de formigas epigéicas que ocorrem em duas estruturas vegetacionais diferentes: mata nativa e cultura de eucalipto. Para a captura das formigas foram utilizadas 800 armadilhas de solo do tipo pitfall, em oito amostras distintas. Um total de 85 espécies, distribuídas em 36 gêneros de sete subfamílias foram coletadas nos dois ambientes, sendo que destas, 83 ocorreram na mata nativa e 60 na cultura de eucalipto. A diversidade de espécies de formigas calculada pelo índice de Simpson não foi significativamente diferente entre os ambientes, ao contrário do resultado obtido a partir da aplicação do índice de Shannon, o qual indicou maior diversidade de espécies na mata nativa. O modelo log-series não se ajustou satisfatoriamente aos dados das comunidades de formigas encontradas na cultura de eucalipto e na mata nativa, mas o modelo log-normal mostrou-se adequado para descrever a estrutura das comunidades dos dois ambientes. O modelo broken-stick, que representa uma comunidade bem estruturada, ajustou-se apenas aos dados da mata nativa.

We compared, through the use of diversity indices and species abundance models, the diversity of communities of epigeous ants occurring in two different vegetational structures: native forest and eucalyptus plantation. To capture the ants, 800 soil pitfall traps were used, in eight sample series. A total of 85 species, belonging to 36 genera of seven subfamilies were collected in the two environments. Of these species, 83 occurred in the native forest and 60 in the eucalyptus plantation. The species diversity as evaluated by Simpson's index was not significantly different between the environments, but the Shannon index indicated a higher diversity of species in the native forest. The log-series model could not be adjusted satisfactorily to the data for the ant communities from either the eucalyptus plantation or the native forest; however, the log-normal model appeared appropriate to describe the community structure in both environments. The broken-stick model, which represents a well-structured community, was only adjusted to the data for the native forest sites.

O presente trabalho procura caracterizar as comunidades de peixes relacionando a variação espacial e temporal com a organização das comunidades de peixes em riachos da bacia do rio Guiraí, Alto Rio Paraná. As amostragens foram realizadas bimestralmente em sete riachos, entre outubro/2006 e agosto/2007 e, para a análise destes dados, utilizamos análises de agrupamento, de similaridade, de variância, de correspondência canônica e árvore de regressão. Foram coletadas 64 espécies de peixes e a variação espacial das comunidades estudadas se mostrou mais evidente que a variação temporal. As variáveis mais importantes na determinação da ocorrência das espécies foram a altitude do trecho amostrado, largura e profundidade do riacho e velocidade da água, o que indica que há interação de fatores em escala regional (altitude) com fatores locais (profundidade, velocidade e largura) na definição da composição de espécies em cada um dos riachos amostrados. O turnover na composição de espécies foi significativamente influenciado pela profundidade e altitude dos riachos. A diferenciação na riqueza e composição de espécies entre os trechos superiores e inferiores da bacia pode permitir o incremento da riqueza em nível regional (bacia hidrográfica) através da diminuição da sobreposição de nichos, permitindo a manutenção de subconjuntos populacionais (para as espécies de distribuição ampla) que podem resistir melhor às alterações antrópicas na estrutura dos habitats.

This paper aims to characterize the fish assemblages and to quantify the importance of spatial and temporal variations on the organization of stream fish assemblages of Guiraí River Basin, Upper Paraná River Basin. The samples were taken every two months in seven streams, from October 2006 to August 2007. To examine these data, we used analysis such as cluster, similarity, variance, canonical correspondence and regression tree. We collected 64 species and the spatial variations of the assemblages were more evident than the temporal ones. The most important variables in determining the occurrence of the species were altitude of the region, stream width and depth and water velocity. This result indicates there is an interaction of regional factors (altitude) with local ones (depth, velocity and width) to define the species composition of each stream. The turnover in species composition was significantly influenced by stream depth and altitude. The differentiation on richness and species composition between upper and lower sites should allow richness increment at regional level (hydrographic basin), decreasing the niches overlap and maintenance of sub-populations (for wide-distributed species) which should to resist more to the antropic action over the habitat structure.