Substrate Preparation Behaviors for the Cultivation of the Symbiotic Fungus in Leaf-Cutting Ants of the Genus Atta (Hymenoptera: Formicidae)

Our findings revealed two distinct patterns of substrate preparation: the pattern of leaf-cutting ants foraging on dicotyledons is marked by highly fragmented substrate resulting in a more advanced initial decomposition. The pattern of leaf-cutting ants harvesting grasses is characterized by large pieces of substrate, resulting in little initial decomposition. Ants foraging on both types of plants are apparently intermediary between the two patterns, although more similar to the patterns of those foraging on dicotyledons. Also, the behavior of scraping the substrate was described for the first time, it is very important for the removal of the epicuticular wax layer of the leaves helping the growth of the symbiotic fungus.

Low variation in ribosomal DNA and internal transcribed spacers of the symbiotic fungi of leaf-cutting ants (Attini: Formicidae)

Leaf-cutting ants of the genera Atta and Acromyrmex (tribe Attini) are symbiotic with basidiomycete fungi of the genus Leucoagaricus (tribe Leucocoprineae), which they cultivate on vegetable matter inside their nests. We determined the variation of the 28S, 18S, and 5.8S ribosomal DNA (rDNA) gene loci and the rapidly evolving internal transcribed spacers 1 and 2 (ITS1 and ITS2) of 15 sympatric and allopatric fungi associated with colonies of 11 species of leafcutter ants living up to 2,600 km apart in Brazil. We found that the fungal rDNA and ITS sequences from different species of ants were identical (or nearly identical) to each other, whereas 10 GenBank Leucoagaricus species showed higher ITS variation. Our findings suggest that Atta and Acromyrmex leafcutters living in geographic sites that are very distant from each other cultivate a single fungal species made up of closely related lineages of Leucoagaricus gongylophorus. We discuss the strikingly high similarity in the ITS1 and ITS2 regions of the Atta and Acromyrmex symbiotic L. gongylophorus studied by us, in contrast to the lower similarity displayed by their non-symbiotic counterparts. We suggest that the similarity of our L. gongylophorus isolates is an indication of the recent association of the fungus with these ants, and propose that both the intense lateral transmission of fungal material within leafcutter nests and the selection of more adapted fungal strains are involved in the homogenization of the symbiotic fungal stock.

Activity of sesame leaf extracts against the symbiotic fungus of Atta sexdens L.

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

Patogenicidade de isolados de três fungos entomopatogênicos a soldados de Atta sexdens sexdens (Linnaeus, 1758) (Hymenoptera : Formicidae)

As formigas cortadeiras atacam diversas culturas agrícolas, pastagens e os reflorestamentos, atuando sobre muitas espécies vegetais. O presente trabalho teve por objetivo avaliar a patogenicidade dos fungos Beauveria bassiana (isolados AM 9 e JAB 06), Metarhizium anisopliae (isolados E 9 e AL) e Paecilomyces farinosus (isolados CG 189 e CG 195) a soldados de Atta sexdens sexdens, em condições de laboratório. Após a coleta em formigueiro isento de produtos fitossanitários, exemplares de soldados foram cuidadosamente separados em grupos de oito indivíduos e, a seguir, banhados em suspensões contendo 1,0 x 10(6), 1,0 x 10(7), 1,0 x 10(8) e 1,0 x 10(9) conídios/mL de cada isolado. em seguida, cada grupo de formigas foi transferido para unidades de câmara úmida e mantido, sem alimentação, a 27 ± 1 ºC. A mortalidade foi verificada diariamente. Os três fungos se mostraram eficientes patógenos, pois provocaram alta mortalidade, matando mais que 80% dos soldados nos quatro primeiros dias após a inoculação. Os melhores isolados foram JAB 06 e AL, na concentração de 1,0 x 10(9) con./mL. Os isolados JAB 06, AL, CG 195 apresentaram maior capacidade de esporular nos cadáveres das formigas e os tempos letais decresceram com o aumento da concentração de conídios usada.

Larval isolation and brood care in Acromyrmex leaf-cutting ants

The larvae of leaf-cutting ants are maintained within the fungus gardens of their colonies and are fed pieces of fungus by the adult workers. However, little else is known about the nature of the worker-larva interaction in these ecologically important ants. To examine whether workers can gauge the needs of individual larvae, we isolated larvae without adult workers for different lengths of time. We then placed workers with the larvae and recorded the type and frequency of the subsequent behaviours of the workers. Workers scraped the mouthparts of larvae, ingested their faecal fluid, fed them with fungal hyphae, transported them around the fungus garden and, most frequently, licked their bodies. The workers were also observed to 'plant' fungal hyphae on the bodies of larvae. Workers interacted more frequently with larvae that had been isolated without workers than with those that had not, but there was no effect of the length of isolation. The results suggest that the interactions are complex, involving a number of behaviours that probably serve different functions, and that workers are to some extent able to assess the individual needs of larvae.

Geographic Distribution and Population Estimate of Leaf-cutting Ants of the Genus Acromyrmex (Hymenoptera: Formicidae) in Southwestern Bahia

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fat body in some genera of leaf-cutting ants (Hymenoptera : Formicidae). Proteins, lipids and polysaccharides detection

The comparative histochemical analysis of the fat body of workers belonging to the basal species Cyphomyrmex rimosus and Mycetarotes parallelus and to derived species Acromyrmex disciger and Atta laevigata revealed that this tissue is constituted mainly by cells denominated trophocytes and oenocytes. The trophocytes of all species studied here were characterized mainly by the proteins and lipids synthesis and storage, being the derived species the ones who have presented higher quantity of lipids in the trophocytes when compared to the trophocytes of basal species. In workers M. parallelus and A. laevigata, besides proteins and lipids, there has being observed the presence of polysaccharides, however, in C. rimosus and A. disciger these elements were detected in lower quantities. The histochemical studies of the oenocytes of basal and derived species revealed significant presence of proteins as well as lipids in these cells. In the oenocytes of derived species A. disciger and A. laevigata a higher quantity of lipidic inclusions has being observed, when compared to the basal species. (c) 2005 Elsevier Ltd. All rights reserved.

The intramandibular gland of leaf-cutting ants (Atta sexdens rubropilosa Forel 1908)

The eusociality developed in Hymenoptera and Isoptera is driven by an efficient interaction between exocrine glands and jointed appendages, both in close interaction with the environment. In this context, the mandible of ants plays an important role, since, in addition to being the main jointed appendage, it possess glandular functions. As an example we might name the two glands associated with the mandible: the mandibular and the intramandibular glands. The intramandibular gland is found inside the mandible and consists of a hypertrophied secretory epithelium and secretory cells in the mandible's lumen. The secretion of the secretory epithelium is liberated through intracuticular ducts that open at the base of hairs at the mandible's surface. The secretion of the intramandibular gland (epithelium and secretory cells) reacted positively to tests for the detection of polysaccharides and proteins, thus suggesting that it consists of glycoproteins. The ultrastructure of the secretor epithelium presents variations related to the developmental stage of the individual, showing a large number of ribosomes and microvilli close to the cuticle in young individuals, while in the older specimens it was possible to note the formation of ail intracellular reservoir. These variations of secretory epithelium, as also the interaction between the cellular groups inside the mandible, are important information about this gland in leaf-cutting ants. (c) 2005 Elsevier Ltd. All rights reserved.

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)

Foraging Behavior and Mortality of Ectatomma brunneum (Hymenoptera, Formicidae) in Simultaneous Exposure to Ant Baits and Conventional Diet in Laboratory

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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.

EFFECT OF SESAME (SESAMUM-INDICUM L) ON NEST DEVELOPMENT OF ATTA-SEXDENS-RUBROPILOSA FOREL (HYM, FORMICIDAE)

The present study showed a strong deleterious effect on leaf-cutting ant Atta sexdens rubiopilosa nests supplied exclusively with sesame (Sesamum indicum) leaves in the laboratory. Sesame leaves were initially attractive to workers and later became antifeedant. Eucaliptus alba and Hibiscus rosa-sinensis leaves were used as control.

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)

Carrying and Effect of Granulated Baits Formulated with Entomopathogenic Fungi among Atta sexdens rubropilosa Colonies (Hymenoptera: Formicidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)