Ultrastructural studies of the mandibular glands of the minima, media and soldier ants of Atta sexdens rubropilosa (Forel 1908)

The mandibular glands of Hymenoptera are structures associated with the mandibles and constitute part of the salivary glands system. Histological studies in workers of Atta sexdens rubropilosa revealed that this gland contains two portions: a secretory and a storage portion or reservoir. Both portions are connected by means of canaliculi. The object of the present work was the study of the ultratructure of the mandibular glands of minima, media and soldier ant of A. s. rubropilosa by TEM techniques. The glands, in the three castes studied, possess a reservoir, constituted by a simple pavementous epithelium surrounded by the cuticular intima and the secretory portion is constituted by cells of rounded shape. The secretory cells, mainly of minima and soldier, were rich in smooth endoplasmic reticulum. The media worker and soldier presented a large number of mitochondria, of varying shape. Well-developed Golgi complexes were also present in the soldiers. The secretory cells in minima, media and soldier were provided with collecting intracellular canaliculi, which were linked to the reservoir through the extracellular portion. The cytoplasm of the canaliculi-forming cell was poor in organelles. In the individuals of the three castes of A. s. rubropilosa, the presence of lipid secretion granules suggested, beyond the other functions, also a possible pheromonal action. The different roles executed by the different insect castes are directly dependent on the glandular products and, consequently, on the secretory cellular characteristics. (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.

Occurrence of Winged Forms of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) in Laboratory Colonies

Foi observada, pela primeira vez no Brasil, a produção de centenas de formas aladas em formigueiros de Atta sexdens rubropilosa Forel, mantidos em laboratório. Larvas de último instar de machos foram encontradas em 5 de agosto de 2000 em um formigueiro com quase seis anos de fundação, contendo aproximadamente 110 L de esponja de fungo distribuída em 21 panelas. Entre 30 e 40 dias mais tarde apareceram larvas de fêmeas aladas. Os adultos sexuados apresentaram tamanhos compatíveis com os encontrados em formigueiros de campo. Foram observadas duas aparentes tentativas frustradas de revoada na última semana de outubro, após o que começaram a aparecer machos e fêmeas mortos no lixo do formigueiro.

Influence of Fungal Contamination on Substrate Carrying by the Leafcutter Ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

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Filamentous fungi found in Atta sexdens rubropilosa colonies after treatment with different toxic bait formulations

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Sobrevivência de operárias de Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) isoladas do formigueiro e alimentadas com dietas artificiais

Avaliou-se dietas artificiais, para operárias médias de Atta sexdens rubropilosa Forel isoladas de formigueiros de laboratório e de campo. Os bioensaios foram realizados com 6 formigas/placa de Petri, sendo 10 placas/tratamento, em câmara ambiental a 24 ± 1 °C e UR > 70%. Não houve diferença na sobrevivência entre as operárias de laboratório e de campo, quando tratadas com dieta artificial líquida. Ao se comparar as dietas artificiais líquida e sólida, pode-se constatar que não houve diferença na sobreviência das operárias de laboratório tratadas com as diferentes dietas. A dieta artificial sólida com troca a cada 48 h, até 25 dias, representa uma alternativa para se trabalhar com operárias médias de A. sexdens rubropilosa, isoladas do formigueiro, em bioensaios de laboratório.

Yeasts associated with nests of the leaf-cutting ant Atta sexdens rubropilosa Forel, 1908

A total of 137 yeasts associated with the leaf-cutting ant Atta sexdens rubropilosa Forel, 1908 were characterized, being selected 93 for analysis. Twenty four species belonging to seven genera(Candida, Cryptococcus, Rhodotorula, Sporobolomyces, Tremella, Trichosporon, Pichia) were isolated from the different analysed material. The genus Candida was widely distributed, with C. homilentoma, C. colliculosa-like, C. famata and C. colliculosa being the most prevalent. A few isolates did not fit the standard descriptions and probably some of them could be new biotypes or even new species. Three strains of black yeasts were also isolated, and four others were identified as being Candida spp. The effective number of yeast species was higher in newer sponge. The origin, distribution and relative importance of these microorganisms for the ants are discussed.

GROWTH OF OOCYTE AND NURSE CHAMBER DURING OOGENESIS IN QUEENS OF THE LEAF-CUTTING ANT ATTA SEXDENS RUBROPILOSA FOREL, 1908 (HYM, FORMICIDAE)

Volume changes of the vitellarium components of the leaf-cutting ant Atta sexdens rubropilosa are reported. The oocyte grew to approximately 409 times of its initial volume and reached a maximum value of 1.2 x 10(7) mu m(3). The follicle increase in size at a more or less constant rate up to the 12(th), showing an elevated growth rate thereafter. The mean number of follicles per ovariole was 16.42 +/- 3.58.

Variability of non-mutualistic filamentous fungi associated with Atta sexdens rubropilosa nests

A survey of the filamentous fungi other than the symbiotic one found in association with Atta sexdens rubropilosa colonies was carried out. Different fungal species (27 taxa) were isolated a few days after treating the workers with toxic baits (sulfluramid; Mirex-SO), from 40 laboratory and 20 field nests. Syncephalastrum racemosum (54 %) and Escovopsis weberi (21 %), Trichoderma harzianum (38 %) and Fusarium oxysporum (23 %) were the prevalent species in laboratory and field nests, respectively. Acremonium kiliense, Acremonium strictum, E. weberi, F oxisporum, Fusarium solani, Moniliella silaveolens and T harzianum were found in both nests' groups. We revealed that many filamentous fungi can co-exist in a dormant state inside the nests of these insects and some of them appear to be tightly associated with this environment.

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.

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

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Density and spatial distribution of Atta sexdens rubropilosa and Atta laevigata colonies (Hym., Formicidae) in Eucalyptus spp. forests

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

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