Digging effort in leaf-cutting ant queens (Atta sexdens rubropilosa) and its effects on survival and colony growth during the claustral phase

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

Growth of populations and the fungus garden of Atta sexdens rubropilosa (Hymenoptera, Formicidae) response to foraged substrates

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

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.

Conservação de pêssegos 'Biuti' por irradiação

Este trabalho teve como objetivo o emprego da radiação gama associada ou não à refrigeração na conservação pós-colheita dos pêssegos 'Biuti'. O comportamento destes frutos foi estudado através de análises físicas (perda de massa fresca, coloração da casca, índice de doença, conservação pós-colheita e firmeza) e químicas (pH, acidez total titulável (ATT), sólidos solúveis totais (SST) e o índice de maturidade, expresso pela relação SST/ ATT). Os frutos colhidos no estádio de maturação fisiológica receberam os seguintes tratamentos: 0,0kGy; 0,1kGy; 0,2kGy; 0,3kGy; 0,4kGy e 0,5kGy através do irradiador GAMMABEAN 650 que tem como fonte o Cobalto 60. Os pêssegos foram armazenados em condições ambientais (24±2ºC; 72-76% UR) por 1 semana e em condições de refrigeração em estufa B.O.D. (0±1ºC; 70-80% UR) por 2 semanas. Analisando os resultados pode-se concluir que as diferentes doses de radiação aplicadas não promoveram o aumento da vida-útil pós-colheita de pêssegos. Os frutos armazenados sob refrigeração tiveram maior vida-útil pós-colheita em relação aos armazenados em temperatura ambiente.

Structural characterization of Botryosphaeran: a (1 -> 3;1 -> 6)-beta-D-glucan produced by the ascomyceteous fungus, Botryosphaeria sp.

The exopolysaccharide, Botryosphaeran, produced by the ligninolytic, ascomycetcous fungus Botryosphaeria sp., was isolated from the extracellular fluid by precipitation with ethanol, and purified by gel permeation chromatography to yield a carbohydrate-rich fraction (96%) composed mainly of glucose (98%). Infra-red and C-13 NMR spectroscopy showed that all the glucosidic linkages were in the beta-configuration. Data from methylation analysis and Smith degradation indicated that Botryosphaeran was a (1 --> 3)-beta-(D)-glucan with approx 22% side branching at C-6. The products obtained from partial acid hydrolysis demonstrated that the side branches consisted of single (1 --> 6)-beta-linked glucosyl, and (1 --> 6)-beta-linked gentiobiosyl residues.[GRAPHICS](C) 2003 Elsevier Ltd. All rights reserved.

Comparison of Botryosphaeran production by the ascomyceteous fungus Botryosphaeria sp., grown on different carbohydrate carbon sources, and their partial structural features

The influence of glucose concentration and other carbohydrates (monosaccharides: fructose, galactose, mannose; polyols: mannitol and sorbitol; disaccharides: lactose, sucrose and commercial sucrose; and industrial sugarcane molasses) were compared as sole carbon sources for the production of Botryosphaeran, an exopolysaccharide (EPS) produced by Botryosphaeria sp. The optimum glucose concentration for EPS production was 50 g 1(-1). With the exception of mannitol, the fungus produced EPS on all carbon sources studied, with highest yields occurring with sucrose followed by glucose. All EPS showed exclusively glucose after acid hydrolysis and monosaccharide analysis. FTIR spectroscopy demonstrated the presence of beta-anomers indicating that all the EPS produced by Botryosphaeria sp. on the different carbon sources were essentially of the beta-D-glucan type.

Anti-Mycobacterium tuberculosis activity of fungus Phomopsis stipata

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

The adaptive potential of a plant pathogenic fungus, Rhizoctonia solani AG-3, under heat and fungicide stress

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Atividade fungitóxica de Momordica charantia L. no controle de Sclerotium rolfsii Sacc.

O fungo Sclerotium rolfsii causa grandes perdas em algumas culturas econômicas. Por produzir estruturas de resistência (escleródios), este fungo é de difícil controle. Há escassez de novos ingredientes ativos eficientes para o controle deste patógeno. Assim, o objetivo do presente trabalho foi verificar se existe atividade fungitóxica na planta Momordica charantia (melão-de-sãocaetano), com potencial futuro para ser estudado no controle de S. rolfsii. Para isso, dois ensaios foram realizados, um in vitro (laboratório) e outro in vivo (câmara de crescimento). em in vitro, escleródios do patógeno ficaram em contato com extratos hidroetanólico e aquoso de folhas e ramos de M. charantia e sem extrato por 7, 14, 21 e 28 dias. A sobrevivência dos escleródios foi avaliada em meio de cultura específico, após cada tempo. em in vivo, testou-se a ação dos mesmos extratos de maneira preventiva e curativa (aplicação aos 6 e 3 dias antes do plantio; no dia do plantio; e aos 3 e 6 dias após o plantio) e no tratamento de semente, no patossistema feijoeiro cv. Carioquinha versus S. rolfsii. A eficiência da ação dos extratos foi avaliada por meio da severidade da doença. Os extratos hidroetanólico e aquoso, in vitro, de forma semelhante, controlaram 100% os escleródios, num período de 0 a 7 dias. No ensaio in vivo, o extrato hidroetanólico, aplicado tanto em 6 ou 3 dias, antes do plantio, de forma preventiva, diminuiu a severidade da doença em 74%. Há atividade fungitóxica na parte aérea da planta de melão-de-são-caetano, com potencial futuro de estudo para controlar S. rolfsii, preferencialmente, de maneira preventiva.

Influence of TLR-2 in the immune response in the infection induced by fungus Sporothrix schenckii

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

Microscopic evidence supports the hypothesis of high cellulose degradation capacity by the symbiotic fungus of leaf-cutting ants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cryptic speciation and recombination in the fungus Paracoccidioides brasiliensis as revealed by gene genealogies

Paracoccidioides brasiliensis is the etiologic agent of paracoccidioidomycosis, a disease confined to Latin America and of marked importance in the endemic areas due to its frequency and severity. This species is considered to be clonal according to mycological criteria and has been shown to vary in virulence. To characterize natural genetic variation and reproductive mode in this fungus, we analyzed P. brasiliensis phylogenetically in search of cryptic species and possible recombination using concordance and nondiscordance of gene genealogies with respect to phylogenies of eight regions in five nuclear loci. Our data indicate that this fungus consists of at least three distinct, previously unrecognized species: S1 (species 1 with 38 isolates), PS2 (phylogenetic species 2 with six isolates), and PS3 (phylogenetic species 3 with 21 isolates). Genealogies of four of the regions studied strongly supported the PS2 clade, composed of five Brazilian and one Venezuelan isolate. The second clade, PS3, composed solely of 21 Colombian isolates, was strongly supported by the alpha-tubulin genealogy. The remaining 38 individuals formed S1. Two of the three lineages of P. brasiliensis, S1 and PS2, are sympatric across their range, suggesting barriers to gene flow other than geographic isolation. Our study provides the first evidence for possible sexual reproduction in P. brasiliensis S1, but does not rule it out in the other two species.

Efficacy of the nematode-trapping fungus Duddingtonia flagrans against infections by Haemonchus and Trichostrongylus species in lambs at pasture

The efficacy of the nematode-trapping fungus Duddingtonia flagrans against infections by trichostrongyle nematodes in sheep was assessed throughout 6 months. Twenty Ile de France lambs were divided into two groups (control and treated groups), which were kept in separate pastures. Animals of the treated group were fed with D. flagrans twice a week (Tuesdays and Fridays). Pellets were prepared with the fungus mycelia in liquid culture medium and contained approximately 20% fungus. They were mixed with the animals' diet at a concentration of 1 g pellet per 10 kg live weight. Faecal egg counts (FEC), packed cell volume (PCV), total serum protein and the animals' body weight were determined fortnightly from 7 October 2005 to 24 March 2006. Comparison of such parameters between groups showed no significant differences (P > 0.05), except on 10 February 2006, when the control group presented a higher mean FEC than the treated group (P < 0.05). Feeding sheep with pellets containing D. flagrans had no benefit to the prophylaxis of nematode infections under the experimental conditions used in the present study.

Substrate distribution in fungus chambers in nests of Atta bisphaerica Forel, 1908 (Hym., Formicidae)

Substrate distribution was studied in three adult colonies of the leaf-cutting ant Atta bisphaerica Forel, 1908 using dye. Some supply holes were mapped using baits made from small plastic straws impregnated with citric pulp. Two holes, equidistant from one another, were then selected in each nest. The colonies were excavated completely 24 h after bait placement. During excavation, fungus chambers were checked for dye. We observed that the dyed baits were distributed in all sectors and at all depths regardless of where the baits had been placed. This supported the hypothesis that toxic baits placed in a single supply hole are uniformly distributed throughout the colony.

Influence of physical and chemical factors during foraging and culture of the symbiont fungus in Atta sexdens rubropilosa (Hymenoptera : Formicidae)

The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study the physical influence factors: filter paper with paraffin, filter paper without paraffin and polyester film. To study the chemical factors, some fragments were impregnated with organic extract of orange albedo, others were soaked with soybean oil and for the remaining ones nothing was applied. The following parameters were evaluated: (i) attractiveness of substrate for transport and number of loading workers per treatment; (ii) foraged material incorporation; (iii) rejection by numbers of fragments deposited in the garbage or beside the fungus garden. All the polyester film fragments carried out to the fungus garden were subsequently rejected. We verified that chemical factors of the substrate were more quickly detected by the workers, whereas physical factors were used as a criterion in the decision-making to reject or accept the substrate collected.