Ant Group Effects on the Insecticide and Dye Flow Among Atta sexdens rubropilosa (Hymenoptera: Formicidae) Workers

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ventilation of the giant nests of Atta leaf-cutting ants: does underground circulating air enter the fungus chambers?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Expressed sequence tags from Atta laevigata and identification of candidate genes for the control of pest leaf-cutting ants.

Leafcutters are the highest evolved within Neotropical ants in the tribe Attini and model systems for studying caste formation, labor division and symbiosis with microorganisms. Some species of leafcutters are agricultural pests controlled by chemicals which affect other animals and accumulate in the environment. Aiming to provide genetic basis for the study of leafcutters and for the development of more specific and environmentally friendly methods for the control of pest leafcutters, we generated expressed sequence tag data from Atta laevigata, one of the pest ants with broad geographic distribution in South America. Results: The analysis of the expressed sequence tags allowed us to characterize 2,006 unique sequences in Atta laevigata. Sixteen of these genes had a high number of transcripts and are likely positively selected for high level of gene expression, being responsible for three basic biological functions: energy conservation through redox reactions in mitochondria; cytoskeleton and muscle structuring; regulation of gene expression and metabolism. Based on leafcutters lifestyle and reports of genes involved in key processes of other social insects, we identified 146 sequences potential targets for controlling pest leafcutters. The targets are responsible for antixenobiosis, development and longevity, immunity, resistance to pathogens, pheromone function, cell signaling, behavior, polysaccharide metabolism and arginine kynase activity. Conclusion: The generation and analysis of expressed sequence tags from Atta laevigata have provided important genetic basis for future studies on the biology of leaf-cutting ants and may contribute to the development of a more specific and environmentally friendly method for the control of agricultural pest leafcutters.

Microbiological changes in the nests of leaf-cutting ants fed on sesame leaves

The number of bacteria and yeasts occurring in the organic matter inside the nests were determined both in colonies of leaf-cutting ants reared on Eucaliptus alba (control) or Sesamum indicum (experimental). Sesame leaves induce imbalance and nests usually die. In control nests the number of bacteria in newer sponge and in older sponge were similar (3.6 x 105 and 1.4 x 105 CFU/g, respectively) whereas in waste deposit the mean reached 7.3 x 107 CFU/g. The most Probable Number (MPN/g) of yeasts were 2.7 x 104, 1.3 x 105/g and 2.2 x 104 for newer sponge, older sponge and waste deposit, respectively. Using material from older sponge for comparison, the number of bacteria and yeasts reared on sesame leaves showed significant differences. The number of bacteria was 3.3 x 107 CFU/g, a value close to that found in waste deposit of normal (control) nests, whereas the number of yeasts was 6.7 x 105/g. These changes in microbial populations due to the effect of sesame leaf uptake could be a significant factor in nest imbalance and mortality when leaf-cutting ants are consuming toxic plants.

Activity of Extracts and Fatty Acids of Canavalia ensiformis (Leguminosae) Against the Symbiotic Fungus of the Leaf-Cutting Ants Atta sexdens

The inhibitory effect of leaves extracts of Carnavalia ensiformis on the development of the symbiotic fungus of the leaf-cutting ants Atta sexdens (Forel) was evaluated. The hexane extract showed highest activity at concentration of 1000 μg/mL. Chromatographic separations of this extract have led to the isolation of a mixture of fatty acids which showed the same activity of the crude extract.

Toxicity of Cipadessa fruticosa to the leaf-cutting ants Atta sexdens rubropilosa (Hymenoptera: Formicidae) and their symbiotic fungus

Crude extracts from fruits, branches and leaves of Cipadessa fruticosa were assayed on Atta sexdens rubropilosa workers and their symbiotic fungus Leucoagaricus gongylophorus. The results showed that the majority of the extract tested reduced significantly (p < 0.05) the survival of the workers comparable to the neem oil. In addition, the dichloromethane extract from fruits and the hexane extract from branches of C. fruticosa inhibited in 80% the development of the symbiotic fungus. The hexane and dichloromethane extracts from fruits of C. fruticosa were fractionated and their fractions were subjected to new bioassays. Several fractions showed relevant activity on ants, but none of them inhibited significantly the fungal growth. The possibility of controlling leaf-cutting ants in the future using C. fruticosa is discussed.

Leaf-cutting ants toxicity of limonexic acid and degraded limonoids from Raulinoa echinata. X-ray structure of epoxy-fraxinellone

Phytochemical survey of roots extracts of the South Brazilian endemic plant Raulinoa echinata Cowan, Rutaceae led to the isolation of known degraded limonoids: fraxinellone, fraxinellonone and epoxy-fraxinellone. The latter was previously isolated also from the stems, but the relative configuration could not be solved by NMR experiments. This paper deals with the X-ray diffraction analysis of epoxy-fraxinellone and its toxicity to leaf-cutting ants, describes the isolation of fraxinellonone and fraxinellone for the first time in Raulinoa. Epoxy-fraxinellone showed no toxicity to the leaf-cutting ants (Atta sexdens rubropilosa). The limonoid limonexic acid, isolated from stems, presented high toxicity to the leaf-cutting ants, diminishing considerably their longevity. ©2005 Sociedade Brasileira de Química.

Toxicity of straight-chain fatty acids to leaf-cutting ants Atta sexdens rubropilosa (Hymenoptera: Formicidae) and the symbiotic fungus Leucoagaricus gongylophorus

This work determined toxicity and attractiveness of straight-chain fatty acids (C 5 to C 12) to Atta sexdens rubropilosa (Forel) workers. The effect to the symbiotic fungus, Leucoagaricus gongylophorus (Singer) Möller, was also tested with the fatty acids C 6 to C 12. A strong mortality of leaf-cutting ants that were fed with an artificial diet containing fatty acids C to C at concentrations above 1.0 mg.ml -1 was observed. Rice flakes impregnated with solutions of these fatty acids were repellent to leaf-cutting ants. Contact experiments showed that treatments with C 6 and C 7 at concentration of 100 mg.ml -1 significantly reduced the survival rate of leaf-cutting ants. The fatty acids C 8 to C 11 were toxic to leaf-cutting ants when topically tested at concentration of 200 mg.ml -1. In relation to the fungus' bioassays, the fatty acids C 6 to C 12 at concentration of 0.1 mg.ml -1 inhibited 100% of the fungal development. Although when the concentration was reduced by half no inhibition effects were observed. The results showed that straight-chain fatty acids have desirable properties for controlling leaf-cutting ants since they directly interfere with both organisms of the symbiotic relationship. The potential of fatty acids as well as ways to control leaf-cutting ants with these compounds are discussed in this article.

Evaluation of the toxicity of Virola sebifera crude extracts, fractions and isolated compounds on the nest of leaf-cutting ants

The phytochemical study of Virola sebifera leaves led to the isolation of three lignans: (+)-sesamin, (-)-hinokinin, and (-)-kusunokinin and three flavonoids: quercetin-3-O - L-rhamnoside, quercetin-3-O - D-glucoside, and quercetin-3-methoxy-7-O - D-glucoside by using techniques as high-speed counter-current chromatography and high-performance liquid chromatography. The crude extracts, fractions, and isolated compounds were evaluated for their insecticidal and fungicidal potential against Atta sexdens rubropilosa and its symbiotic fungus Leucoagaricus gongylophorus. The bioassay results showed a high insecticidal activity for the methanol crude extract of the leaves of V. sebifera and its n-hexane, dichloromethane and ethyl acetate fractions. The fungicidal bioassay revealed high toxicity of the lignans against L. gongylophorus. © 2012 Keylla Utherdyany Bicalho et al.

Foraging of psilocybe basidiocarps by the leafcutting ant acromyrmex lobicornis in Santa Fé, Argentina

Background It is generally accepted that material collected by leaf-cutting ants of the genus Acromyrmex consists solely of plant matter, which is used in the nest as substrate for a symbiotic fungus providing nutrition to the ants. There is only one previous report of any leaf-cutting ant foraging directly on fungal basidiocarps. Findings Basidiocarps of Psilocybe coprophila growing on cow dung were actively collected by workers of Acromyrmex lobicornis in Santa Fé province, Argentina. During this behaviour the ants displayed typical signals of recognition and continuously recruited other foragers to the task. Basidiocarps of different stages of maturity were being transported into the nest by particular groups of workers, while other workers collected plant material. Conclusions The collection of mature basidiocarps with viable spores by leaf-cutting ants in nature adds substance to theories relating to the origin of fungiculture in these highly specialized social insects. © 2013 Masiulionis et al.

Microsatellite loci characterized in the leaf-cutter ant Atta laevigata

Background: The leaf-cutter ant Atta laevigata (Formicidae: Attini) is an agricultural pest largely distributed in the Neotropics and a model organism for studies of evolution, speciation and population genetics. Microsatellites are a very powerful tool for these kind of studies, but such markers are not available for studies on A. laevigata. In the present report, we describe the isolation and characterization of nine microsatellite loci in A. laevigata and the testing of these markers across other species of leaf-cutter ants. Findings. Nine microsatellite loci, consisting of six dinucloeotide, one trinucleotide, one tetranucleotide, and one di/trinucleotide repeat motifs, were isolated and characterized. Primers and protocols were successfully designed to selectively amplify these markers. To test effectiveness of these markers for detailed population genetic studies, we genotyped female workers collected from 36 monogynic nests of A. laevigata and found that eight loci were within Hardy-Weinberg expectations, while the remaining locus had a deficiency of heterozygotes. Micro-Checker analysis of individuals from 55 monogynic nests indicated that loci Alae11, Alae24, Alae18 showed signs of null alleles. For the remaining six loci, the number of alleles per locus ranged between 2 and 11, with expected heterozygosity ranging between 0.07 and 0.88. All of these loci cross-amplified in other species of Atta. Conclusions: These six polymorphic microsatellite loci should prove useful for future genetic investigations of the pest species Atta laevigata, as well as studies of other species of leaf-cutter ants in the genus Atta. © 2013 Kakazu et al.; licensee BioMed Central Ltd.

The Mitochondrial Genome of the Leaf-Cutter Ant Atta laevigata: A Mitogenome with a Large Number of Intergenic Spacers

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Starmerella aceti f.a., sp nova, an ascomycetous yeast species isolated from fungus garden of the leafcutter ant Acromyrmex balzani

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Mitochondrial and peroxisomal population in post-pharyngeal glands of leaf-cutting ants after lipid supplementation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)