Alimentary preconditioning in Acromyrmex subterraneus brunneus workers

Ants suffer a strong environmental influence and are sometimes conditioned for many social activities. To understand better this phenomenon in leaf-cutting ants, 24 colonies of Acromyrmex subterraneus brunneus (Hymenoptera: Formicidae) were conditioned for 2 months with 6 different plants (Citrus spp., Ligustrum spp., Acalypha spp., Eucalyptus spp., Alchornea triplinervia, Melia spp.), to verify alimentary preconditioning in plant selection. After the conditioning period, plants were offered simultaneously, to evaluate the acceptability of each plant species. During foraging, the workers did not exhibit alimentary source fidelity, which was familiarized. This fact suggests the absence of alimentary preconditioning, reinforcing the polyphagic foraging behavior of leaf-cutting ants.

Ecological interaction between Atta sexdens (Hymenoptera: Formicidae) and the vegetation of a mesophyll semideciduous forest fragment in Botucatu, SP, Brazil

Among 89 plants species growing in a subtropical dry forest fragment located in Botucatu, State of São Paulo, Brazil, 35 species were cut by Atta sexdens, representing 39.34% of the current plants existing in this area. A. sexdens L., 1758 (Hymenoptera: Formicidae) has a selective preference for the following species: Alchornea triplinervia, Faramea cyanea, Cariniana estrellensis and Casearea obliqua, with the first being the most cut species. The frequency and absolute densities of the plant families and species significantly influence the selection process. When comparing the absolute frequency regarding the 10 most cut plant species and the cutting frequency, significant data were obtained only for the euphorbiaceous A. triplinervia species, proving the preference of A. sexdens for this species in particular. These interactions are discussed based on ecological and management factors in agro-ecosystems.

HPLC-EICD: An Useful Tool for the Pursuit of Novel Analytical Strategies for the Detection of Antioxidant Secondary Metabolites

Living cells are continuously exposed to a variety of challenges that exert oxidative stress and are directly related with senescence and the onset of various pathological conditions such as coronary heart disease, rheumatoid arthritis and cancer. Nevertheless, living organisms have developed a complex antioxidant network to counteract reactive species that are detrimental to life. With the aim of bio-prospecting plant species from the Brazilian Cerrado and Atlantic Forest, we have established a methodology to detect secondary antioxidant metabolites in crude extracts and fractions obtained from plant species. Combining HPLC with an electrochemical detector allowed us to detect micromolecules that showed antioxidant activities in Chimarrhis turbinata (DC) leaf extracts. Comparison with purified flavonoid standards led us to identify the compounds in their natural matrices giving valuable information on their antioxidant capacity.

Fruit and seed exploitation by small rodents of the Brazilian Atlantic forest

In the Brazilian Atlantic forest (BAF) there are at least 57 rodent species and most of them are considered omnivorous. These species feed, more or less frequently, on fruits and seeds. Nevertheless the potential role of each species as frugivorous, seed predator or seed disperser is still unclear. In the present study we analyzed patterns of fruit and seed exploitation by eight small rodent species from an Atlantic Forest site. We offered to captive animals fruits of 30 plant species (23 genera, 15 families). After 48 h we recorded consumption patterns of pulp/aril and seed. Rodent species differed in their patterns of fruit and seed exploitation. The smallest species, Akodon serrensis, Oligoryzomys nigripes, and Wilfredomys pictipes (body size range : 26-45 g), and also the medium-sized Oecomys aff. concolor (84 g) fed mainly on pulp and also on small to medium-sized seeds (< 10 mm diameter). The medium-sized rodent, Oryzomys russatus (91 g) fed on pulp and also on seeds with diameter ≤ 15 mm. Thus larger seeds remain intact after being manipulated by such species. The medium-sized Delomys dorsalis (72 g) and the larger Trinomys iheringi (274 g) and Nectomys squamipes (253 g) form a third group, which consumed both fruit and seed of most species independent of their size. These later two species and also O. russatus are probably the main seed predators in the rodent community of the BAF.

Comportamento do cafeeiro apoatã em consórcio com culturas anuais

This study was conducted in Adamantina, region of Alta Paulista, São Paulo State, Brazil, from 1989 to 1993. Yield of Apoatã coffee (Coffea canephora Pierre ex Froehner) was evaluated during four years of intercropping with five plant species: IAC 20 - cotton (Gossypium hirsutum L.); cv. Tatu - peanut (Arachis hypogaea L.); IAC 165 - rice (Oryza sativa L.); cv. Guarani - castor bean (Ricinus communis L.) and IAC 100-B - corn (Zea mays L.). The crops were seeded 50 cm apart from coffee canopy. The treatments were arranged in randomized complete block design with five replications. Yield was significantly decreased when coffee was intercropped with castor bean, corn, cotton and peanut, but height and diameter of orthotropic branches were not affected. Linear correlation analysis showed that coffee yield was inversely correlated with the dry biomass of the intercrops.

Interações entre aves frugívoras e plantas em um fragmento de mata atlântica de Minas Gerais

We studied the frugivorous birds and their fruiting plants during two years in a forest fragment in Viçosa, Minas Gerais State, Brazil. Our aim was to identify the importance of birds and plants based on an importance index that comprise both the number of interactions and interaction exclusiveness. Twentynine bird species and 25 plant species were recorded. Small birds (< 100 g) comprised 85% of the interactions, and Chiroxiphia caudata reached the largest importance index (0.296), with 12 interactions, being six exclusive. Among plants, the melastome Miconia cinnamomifolia reached the largest importance index (0.277), interacting with 72.4% (21) of the bird species. This study showed that seed dispersal by small birds couldn't be underestimated because they disperse seeds of many plant species, even in pristine forests. Studies like this are also important to list the main food resources to frugivorous birds that could be used in management plans.

Absorption and translocation of 2,4-D in plants of Memora peregrina

The objective of this work was to evaluate absorption and translocation of the herbicide 2,4-D in plants of Memora peregrina. The herbicide 2,4-D was used alone with the formulation DMA 806 BR and associated with the herbicide picloram in the commercial product Padron. Levels of radioactivity on the treated leaves were determined in sample obtained after washing them with methanol and chloroform at different times after the application of the radiolabelled formulation (1, 2, 4, 8, 24, and 48 h). Translocation was evaluated by cutting plants between stem and root. The parts obtained were: root, stem, leaf treated, leaves above the leaf treated, leaves below the leaf treated, and leaf opposite of the leaf treated. These parts were weighted, dried, ground, burnt, and radioactivity in the samples was determined. The results suggest that the translocation of the radioactive herbicide 2,4-D was insignificant in plants of M. peregrina in the two treatments evaluated. Absorption of 14C 2,4-D in the treatment with DMA 806 BR and the mixture of DMA 806 BR plus Padron had the same behavior. These observations explain the inefficient control obtained with this herbicide in plant species under study.

Inhibition of the symbiotic fungus of leaf-cutting ants by coumarins

Leaf-cutting ants are known to be a serious pest for agriculture due to the high amounts of vegetal matter from crops used by them in order to cultivate a symbiotic fungus on which they rely for food and enzymes. The mutualism between the fungus and the ants is a point to be explored when alternative methods of control are being thought of. Considering that some plants are naturally resistant to phytophagous insects, some natural products (secondary metabolites) should be evaluated with respect to their insecticide and/or fungicide properties. In this paper we isolated eight coumarins from four different plant species and we determined their effect on the development of the symbiotic fungus of the leaf-cutting ant Atta sexdens. With the exception of clausarin, all the other coumarins were inhibitory from 64 μg mL-1 through 80 μg mL-1 and xanthyletin inhibited the fungus at 25 μ mL -1. ©2005 Sociedade Brasileira de Química.

Brosimum gaudichaudii Trecul (Moraceae): Da planta ao medicamento

The chemical, biological, pharmacological and toxicological study of plants used in medical treatments by different societies around the world has been intensifying over the years, primarily in the search for new herbal, homeopathic or even allopathic medicines. Motivated by this interest, we are investigating some Brazilian plant species, among them a tree, Brosimum gaudichaudii Trecul (Moraceae), found in Brazil's savannah-like prairies and scrub-forest (cerrado) and mesophytic forest. Several extracts have been made and separated into fractions and some compounds have been isolated - principally coumarins - and their respective structures analyzed by spectrophotometric and other methods. By collaborating with researchers in other fields, we have been able to carry out various bioassays and even basic clinical tests, namely: determination of anti-helminthic, anti-microbial, photosensitizing, anticancer and mutagenic activities, toxicological and pathogenic studies, with the aim of discovering a genuinely Brazilian herbal or homeopathic medicine.