Occurrence of Atta laevigata (Hymenoptera: Formicidae) in the South of Espirito Santo State, Brazil. Recently Introduced or Endangered Species?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

THE POPULATION STATUS OF THE ENDANGERED BRAZILIAN ENDEMIC LEAF-CUTTING ANT ATTA-ROBUSTA (HYMENOPTERA, FORMICIDAE)

The population status of the endemic leaf-cutting ant Atta robusta was assessed using extensive field surveys. In the coastal plain of the state of Rio de Janeiro, we found localized populations of A. robusta, bur no evidence of population recruitment. In disturbed habitats, A. robusta is apparently being displaced by Atta sexdens rubropilosa.

Validação de sistema de amostragem para monitoramento de formigas cortadeiras atta spp. (Hymenoptera: formicidae) em plantações de eucalipto

Pós-graduação em Ciência Florestal - FCA

Morfogênese de ninhos iniciais de atta spp. (Hymenoptera: formicidae), mortalidade em condições naturais e avaliação da ação de fungos entomopatogênicos

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Comparative morpho-physiology of the metapleural glands of two Atta leaf-cutting ant queens nesting in clayish and organic soils

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

Starch metabolism in Leucoagaricus gongylophorus, the symbiotic fungus of leaf-cutting ants

Leucoagaricus gongylophorus, the symbiotic fungus of the leaf-cutting ants, degrades starch, this degradation being supposed to occur in the plant material which leafcutters forage to the nests, generating most of the glucose which the ants utilize for food. In the present investigation, we show that laboratory cultures of L. gongylophorus produce extracellular alpha-amylase and maltase which degrade starch to glucose, reinforcing that the ants can obtain glucose from starch through the symbiotic fungus. Glucose was found to repress a-amylase and, more severely, maltase activity, thus repressing starch degradation by L. gongylophorus, so that we hypothesize that: (1) glucose down-regulation of starch degradation also occurs in the Atta sexdens fungus garden; (2) glucose consumption from the fungus garden by A. sexdens stimutates degradation of starch from plant material by L. gongylophorus, which may represent a mechanism by which Leafcutters can control enzyme production by the symbiotic fungus. Since glucose is found in the fungus garden inside the nests, down-regulation of starch degradation by glucose is supposed to occur in the nest and play a part in the control of fungal enzyme production by leafcutters. (c) 2005 Elsevier GmbH. All rights reserved.

Triterpene benzoates from the bark of Picramnia teapensis (Simaroubaceae)

Two new benzoic acid esters of triterpene alcohols [lup-20 (29)-en-28-oic acid 3 alpha, 7 beta -dibenzoate and 3 alpha -hydroxy-lup-20(29)-en-28-ic acid 7 beta -benzoate] were isolated from the stem bark of Picramnia teapensis Tul. The structures of these compounds were established on the basis of spectral analyses. Other known compounds, beta -sitosterol, estigmasterol, lupeol and epilupeol, were identified in mixture by GC-MS. The triterpene esters have not shown in-vitro inhibitory effect on the growth of Leucoagaricus gongylophorus (Fisher), referred also as Leucocoprinus gongylophorus (Heim), syn Rozites gongylophora (Moller), the symbiotic fungus cultivated by the leaf-cutting ant Atta sexdens L.

Evaluation of the adequacy of diflubenzuron and dechlorane in toxic baits for leaf-cutting ants (Hymenoptera : Formicidae) based on formicidal activity

Studies assessing the characteristics of active ingredients (AIs) of toxic baits for leaf-cutting ants are still scarce, although the need for a delayed action of these compounds on adult workers has been well accepted (mortality <= 15% at 24 h and <= 90% at 21 days). Therefore, we determined the insecticidal action of two AIs used in commercial baits, diflubenzuron and dechlorane, over time in workers, and discussed the control of colonies in relation to the existing literature. Dechlorane presented excellent insecticidal activity with a delayed action at all concentrations tested, although its commercial use has been prohibited due to its organochlorine nature. In contrast, diflubenzuron did not cause significant mortality or symptoms of intoxication, indicating that the successful cases reported with the use of baits containing this AI were in fact due to an accidental contamination with dechlorane. We comment about the ineffectiveness of diflubenzuron on alternative targets, i.e., young forms and the mutualistic fungus, supporting the concept that the AI needs to a have a delayed action on adult workers.

Nest Digging by Leaf-Cutting Ants: Effect of Group Size and Functional Structures.

Leaf-cutting ant workers dig underground chambers, for housing their symbiotic fungus, interconnected by a vast quantity of tunnels whose function is to permit the entrance of food (leaves), gaseous exchanges, andmovement of workers, offspring, and the queen. Digging is a task executed by a group of workers, but little is known about the group effect and group-constructed functional structures. Thus, we analyzed the structures formed by worker groups (5, 10, 20, and 40 individuals) of the leaf-cutting ant, Atta sexdens rubropilosa, for 2 days of excavation. The digging arena was the same for the 4 groups, with each group corresponding to a different density. Our results verified a pattern of tunneling by the workers, but no chamber was constructed. The group effect is well known, since the 40-worker group dug significantly more than the groups of 5, 10, and 20. These groups did not differ statistically from each other. Analysis of load/worker verified that workers of the smallest group carried the greatest load. Our paper demonstrates the group effect on the digging of nests, namely, that excavation is proportional to group size, but without emergence of a functional structure such as a chamber.

Leaf-cutting ant faecal fluid and mandibular gland secretion: effects on microfungi spore germination

The mandibular gland secretion (MGS) and the faecal fluid (FF) of the leaf-cutting ant Atta sexdens rubropilosa Forel affected the spore germination of selected microfungi isolated from nests of this insect. MGS was more effective than the FF, completely inhibiting the spore germination of four out of six microfungi species.

Activities of Extracts and Compounds from Spiranthera odoratissima St. Hil. (Rutaceae) in Leaf-cutting Ants and their Symbiotic Fungus

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biological Activity of Quinoline Alkaloids from Raulinoa echinata and X-ray Structure of Flindersiamine

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

Attractiveness of copperleaf-based bait to leaf-cutting ants

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

Toxicity of lignans to symbiotic fungus of leaf-cutting ants

Lignans from Virola sebifera Aubl., Virola sp., and Otoba parvifolia (Mkfg.) A. Gentry (Myristicaceae) inhibited the in vitro growth of the fungus cultivated by leaf-cutting ants of the species Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae). A comparison of activity among the lignans was obtained.

Toxicity of synthetic piperonyl compounds to leaf-cutting ants and their symbiotic fungus

The development of Leucoagaricus gongylophorus, the fungus cultured by the leaf-cutting ant Atta sexdens was inhibited in vitro by synthetic compounds containing the piperonyl group. In addition, worker ants that were fed daily on an artificial diet to which these compounds were added had a higher mortality rate than the controls. The inhibition of the fungal growth increased with the size of the carbon side chain ranging from C1 through C8 and decreasing thereafter. 1-(3,4-Methylenedioxybenzyloxy)octane (compound 5) was the most active compound and inhibited the fungal development by 80% at a concentration of 15 μg m1-1. With worker ants the toxic effects started with compound 5 and increased with the number of carbons in the side chain. Thus, for the same concentration (100 μg m1-1) the mortality rates observed after 8 days of diet ingestion were 82%, 66% and 42%, for 1-(3,4-methylenedioxybenzyloxy)decane, 1-(3,4-methylenedioxybenzyloxy)dodecane and compound 5, respectively, whereas with commercial piperonyl butoxide the mortality was 68%. The latter compound, which is known as a synergist insecticide, was as inhibitory to the symbiotic fungus as the synthetic compound 5. The possibility of controlling these insects in the future using compounds that can target simultaneously both organisms is discussed. © 2001 Society of Chemical Industry.