ABSTRACT Amphibians inhabiting agricultural areas are constantly exposed to large amounts of chemicals, which reach the aquatic environment during the rainy season through runoff, drainage, and leaching. We performed a comet assay on the erythrocytes of tadpoles found in the surroundings of agricultural fields (soybean and corn crops), where there is an intense release of several kinds of pesticides in different quantities. We aimed to detect differences in the genotoxic parameters between populations collected from soybeans and cornfields, and between them and tadpoles sampled from non-agricultural areas (control group). Tadpoles collected from ponds located at soybean fields had significantly more DNA damage, followed by tadpoles collected from cornfields. In contrast, animals sampled from non-agricultural areas had the lowest incidence of DNA damage. In addition, we found a negative correlation between the parameters of the comet assay and the area of the ponds surrounding soybean. This correlation indicates a possible dilution effect in the concentration of pesticides. Finally, Physalaemus cuvieri Fitzinger, 1826 seems to be a good bioindicator for detecting the genotoxic effects of field agricultural insecticides; therefore, we suggest that this species should be used in environmental biomonitoring studies, since it is common and abundant where it occurs.

A classificação dos sistemas de acasalamento em Odonata geralmente baseia-se na habilidade dos machos em controlar o acesso das fêmeas aos recursos necessários à postura dos ovos. O objetivo deste artigo foi determinar os critérios de seleção de locais para a defesa de territórios para machos das espécies Perithemis mooma Kirby e Orthemis discolor (Burmeister) (Libellulidae), em Viçosa, controlando a disponibilidade de poleiros e de vegetação aquática. Machos de P. mooma defenderam territórios com vegetação e seus critérios de escolha devem estar relacionados com a oferta de recursos para a postura dos ovos para fêmeas. Machos de O. discolor defenderam territórios em locais com poleiros altos e essa escolha talvez esteja relacionada à possibilidade de visualizar rapidamente qualquer fêmea que se aproxime para copular. A interação com outra espécie de Libellulidae mais ativa e agressiva, Planiplax phoenicura (Ris), alterou a preferência dos machos de O. discolor, o que deixa clara a importância da composição da comunidade e das interações na seleção de microhábitats.

Classifications in mate systems of Odonata are generally based in the male ability to control the female access to oviposition resources. In this paper we discuss the criteria for male territory selection in the dragonflies Perithemis mooma Kirby and Orthemis discolor (Burmeister) (Libellulidae), in Viçosa, Brazil, controlling the availability of perches and aquatic vegetation. P. mooma males defended territories with vegetation and thus their choice was probably related to the oviposition resource of the females. O. discolor males preferred sites with tall perches, possibly because their choice was related to a mate-seeking resource. Interactions with another libellulid more active and aggressive, Planiplax phoenicura (Ris), changed the preference of O. discolor males to vegetated areas highlighting the influence of community composition and interactions on territorial site selection.

The effect of riparian deforestation and stream impoundments on an odonate community was studied in áreas of surviving Atlantic forest in Viçosa and in Rio Doce State Park (PERD), Marliéria, Minas Gerais, Brazil. During 1997 16 species of Libellulidae, 4 Coenagrionidae, 2 Gomphidae, 2 Calopterygidae, 1 Megapodagrionidae, 1 Aeshnidae and 3 Protoneuridae were collected. In Viçosa, the association of sampled odonates with lotic or lentic systems, and in PERD for areas with or without riparian vegetation were compared. The results suggest that although overall odonate taxonomic richness is high in areas without riparian vegetation. Likely, because productivity increase of such areas and its invasion by lentic Odonata species.

A atratividade de fêmeas de Euschistus heros (F.) (Hemiptera: Pentatomidae) aos oito estereoisômeros do 2,6,10-trimetiltridecanoato de metila, principal componente do feromônio sexual produzido pelos machos da espécie, foi estudada em olfatômetro de dupla escolha. Os bioensaios demonstraram que o estereoisômero (2R, 6R, 10S) foi necessário para a atratividade das fêmeas até a fonte de odor, destacando-se em relação aos outros. Apesar de exercer atratividade significativa para as fêmeas, a mistura de estereoisômeros quando comparada ao (2R, 6R, 10S) apresentou menor atratividade.

The attractiveness of Euschistus heros (F.) (Hemiptera: Pentatomidae) females to the eight stereoisomers of the methyl 2,6,10-trimethyltridecanoate, major component of the sex pheromone produced by the males of this species, was studied in a double choice olfactometer. Bioassays showed that the (2R, 6R, 10S) stereoisomer was necessary for the attractiveness of females, presenting better results in relation to the others. The stereoisomeric mixture was shown to present significative attractiveness to females, however, when compared to the (2R, 6R, 10S) stereoisomer, it showed lower attractiveness.

Para o estudo dos aspectos genéticos envolvidos na divisão de trabalho em Melipona quadrifasciata foram construídas colônias de observação contendo apenas operárias jovens originadas de 10 colônias. Em todos comportamentos analisados houve uma grande variação entre as origens, mas somente os comportamentos de construção de células de cria e propolisação apresentaram diferenças significativas entre as origens

Observation colonies containing only young workers from 10 matrix colonies were set up to investigate the genetic aspects involved in task division in Melipona quadrifasciata. Wide variation among origins was observed for all behaviors analyzed, but these differences were significant only for brood cell construction and propolis preparation