Population dynamics, life stage and ecological modeling in Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The role of habitat heterogeneity for the functional response of the spider Nesticodes rufipes (Araneae : Theridiidae) to houseflies

We investigated whether or not different degrees of refuge for prey influence the characteristic of functional response exhibited by the spider Nesticodes rufipes on Musca domestica, comparing the inherent ability of N. rufipes to kill individual houseflies in such environments at two distinct time intervals. To investigate these questions, two artificial habitats were elaborated in the laboratory. For 168 h of predator-prey interaction, logistic regression analyses revealed a type 11 functional response, and a significant decrease in prey capture in the highest prey density was observed when habitat complexity was increased. Data from habitat 1 (less complex) presented a greater coefficient of determination than those from habitat 2 (more complex), indicating a higher variation of predation of the latter. For a 24 h period of predator-prey interaction, spiders killed significantly fewer prey in habitat 2 than in habitat 1. Although prey capture did not enable data to fit properly in the random predator equation in this case, predation data from habitat 2 presented a higher variation than data from habitat 1, corroborating results from 168 h of interaction. The high variability observed on data from habitat 2 (more complex habitat) is an interesting result because it reinforces the importance of refuge in promoting spatial heterogeneity, which can affect the extent of predator-prey interactions.

New mariner elements in Anastrepha species (Diptera: Tephritidae)

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

Morphological aspects of cluster formation in the germarium of the sugarcane borer Diatraea saccharalis Fabricius (Lepidoptera : Pyralidae)

Diatraea saccharalis F. is one of the greatest pests of the sugar cane culture. This report aimed to characterize the germanium region of the sugarcane borer by light and transmission electron microscopy, emphasizing the morphological steps of the ovarian cluster formation. In the germanium of this insect, four zones could be morphologically identified during the cluster formation. In the most apical end of each ovariole - Zone I - the germ line stem cells undergo complete mitotic division, originating the cystoblasts. In the Zone II, each cystoblast produces a group of eight cells, the cystocytes, which are interconnected by the ring canals. Clusters containing all the cystocytes in the meiosis, characterizes the Zone III. Germ cells with ultrastructural features of apoptosis are also detected in this Zone. In the Zone IV the cystocytes differentiate, morphologically, into one oocyte and seven nurse cells. Interstitial somatic cells and pre-follicle cells exhibit, in their cytoplasm, heterogeneous vacuoles containing degenerated cellular fragments, characterized as apoptotic bodies. Our results pointed out to the morphological evidences related with important control mechanisms for new clusters/follicles production and for the cellular arrangement into the germanium, resulting from the programmed cell death. We believe that the morphological characterization of ovarian cluster formation in D. saccharalis provided valuable information for the understanding of the initial steps of oogenesis and contributed for the knowledge of the cellular mechanisms related with the oocyte production and with reproduction in insects.

Inflammatory reaction to the human bot-fly, Dermatobia hominis, in infested and reinfested mice

Two groups of mice were infested with first stage larvae of the human bot-fly, Dermatobia hominis (Linnaeus Jr) (Diptera: Oestridae). In the first group, skin biopsies were carried out 1, 3, 5, 7, 10 and 18 days after infestation. The second group was also infested but had all the larvae removed 5 days after infestation. The mice in the latter group were reinfested 4 weeks later and skin biopsies were carried out 1, 3, 5, 7, 10 and 18 days after reinfestation. In the first group, an inflammatory reaction began slowly, the neutrophils being the main inflammatory cells, eosinophils being scarce. The reaction progressed with time, developing a necrotic halo around the larvae containing inflammatory cells surrounded by fibroblasts. The inflammation invaded the adjacent tissue. In the second group, the inflammatory reaction was intense on the day immediately after reinfestation, the pattern being changed by the presence of a large number of eosinophils. Activated fibroblasts surrounding the necrotic area around the larvae appeared 3 days after reinfestation in the second group and 7 days after infestation in the first group. The results demonstrated that the previous contact with the antigens elicited the early arrival of eosinophils, probably through the chemotactic factors liberated by mast cells in the anaphylactic reaction.

Morphometric study of the midgut epithelium in larvae of Diatraea saccharalis Fabricius (Lepidoptera: Pyralidae)

A larva de Diatraea saccharalis Fabricius (broca-da-cana) tem grande interesse econômico, pois afeta o cultivo e aproveitamento industrial da cana-de-açúcar. Entretanto, poucos são os estudos sobre a morfologia interna desse inseto. O objetivo deste trabalho foi estudar, morfometricamente, o seu epitélio intestinal, ao longo de seu comprimento, visando caracterizar regiões estruturalmente diferentes. O intestino médio de larvas no último instar foi subdividido em três regiões: proximal, mediana e distal e os fragmentos foram processados para observação em microscopia de luz. Os cortes histológicos foram analisados em sistema computadorizado de análise de imagens para medir comprimento, largura e área do epitélio, das diferentes células epiteliais, dos seus respectivos núcleos e do lúmen intestinal. Os dados obtidos foram submetidos ao teste estatístico de Kruskal-Wallis e à análise multivariada. Nossos resultados mostraram que o intestino médio apresentou-se constituído, morfometricamente, por duas diferentes regiões, proximal e distal; a região mediana apresentou valores coincidentes tanto com a região proximal quanto com a distal, sugerindo ser região intermediária. As células epiteliais (colunares, caliciformes e regenerativas), quando avaliadas pela análise estatística multivariada, não apresentaram diferença morfométrica nas diferentes regiões do intestino médio. Entretanto, a análise de variância, realizada para variáveis isoladas, mostrou que as células regenerativas apresentaram maior variabilidade morfométrica.

Morphological study of the hindgut in larvae of Anticarsia gemmatalis Hübner(Lepidoptera: Noctuidae)

A lagarta da soja (Anticarsia gemmatalis Hübner) tem grande interesse econômico, pois afeta significativamente a cultura da soja em todo o mundo. Este trabalho descreve a morfologia do intestino posterior de larvas de A. gemmatalis, com ênfase nos seus aspectos histológicos. O intestino posterior é constituído por regiões morfologicamente distintas, identificadas como piloro, íleo, cólon e reto. Independente da região, a parede do intestino posterior é constituída por fina cutícula, epitélio simples e camada muscular. A íntima cuticular apresenta espículas no anel intersticial posterior, entre o intestino médio e o posterior, e na região posterior do piloro. A musculatura do reto é formada por camada única de largas fibras circulares, diferindo das demais regiões do intestino posterior que apresentam duas camadas de fibras musculares. As extremidades distais dos túbulos de Malpighi atravessam as paredes do reto, constituindo o sistema criptonefridial característico de Lepidoptera.

Morphological regional differences of epithelial cells along the midgut in Diatraea saccharalis Fabricius (Lepidoptera : Crambidae) larvae

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

Mitochondrial DNA polymorphism and heteroplasmy in populations of Aedes aegypti in Brazil

The tropical mosquito Aedes aegypti (Diptera: Culicidae) is the most important domestic vector of urban yellow fever and dengue viruses. Ae. aegypti originated from Africa and was probably introduced into Brazil during the colonial period through embarkations, and dengue epidemics soon followed. Genetic analysis of 12 Ae. aegypti populations from five states in Brazil was conducted based on two mitochondrial DNA fragments: cytochrome oxidase I and NADH dehydrogenase subunit 4. Analyses comparing individual haplotypes indicated the existence of two well-defined clades, probably representing two mitochondrial lineages. Analysis of molecular variance showed significant variability in genetic structure among collections within groups. Mantel regression analysis showed a correlation between genetic and geographic distances, mainly because of northern and northeastern populations, in comparison with those in the southeast. The population from Santos, the largest port in Brazil, showed the greatest diversity, with 10 unique haplotypes, an indication of recent introductions that have not yet spread to other Brazilian cities. Different mitochondrial DNA sequences were found in three specimens, indicating the presence of heteroplasmy.

Megaselia scalaris (Diptera : Phoridae) causing myiasis in Crotalus durissus terrificus (Serpentes : Viperidae) in Brazil

We describe a case of myiasis in Crotalus durissus terrificus (Laurenti) caused by Megaselia scalaris (Loew). The snake was Found in Anhembi, São Paulo, Brazil, with a lesion measuring 25 mm in diameter where the larvae of M. scalaris had penetrated the ribs. The opportunistic behavior of the larvae of M. scalaris is discussed.

Possible causes of spatial variability in Diatraea saccharalis Fabr. (Lep., Crambidae) and its parasitoid populations in sugarcane fields in Brazil

Based on the large data set stored in some sugarcane mills regarding the biological control programme of Diatraea saccharalis using the parasitoids Cotesia flavipes and tachinid flies, the aim of the present study was to determine whether sugarcane varieties, number of cuts and plant ages are major determinants in promoting spatial variability in D. saccharalis, C. flavipes and tachinid fly populations in sugarcane fields in the state of São Paulo (Brazil). The data set used to support this study was provided by the Sao Joao and Barra sugarcane mills. Coefficient of variation was adopted as a measure of the spatial variability of population density. Spatial variability was estimated for the total density of D. saecharalis (parasitized + unparasitized larvae), and also for D. saccharalis larvae parasitized by tachinids and by C. flavipes. Statistical analysis revealed that the spatial variation in D. saccharalis populations was influenced by the number of cuts and by plant ages in the Barra and Sao Joao Mills, respectively. Similar results were obtained for D. saccharalis larvae parasitized by tachinids; however, in the Sao Joao Mill, the spatial variability of these populations was also influenced by the different number of varieties. Finally, considering D. saccharalis larvae parasitized by C. flavipes, no significant regressions with any of the three categories were observed for both sugarcane mills. The multitrophic implications for this agricultural system are also discussed.

Evidences of non-additive effects of multiple parasitoids on Diatraea saccharalis Fabr. (Lep., Crambidae) populations in sugarcane fields in Brazil

Biological control is a relatively benign method of pest control. However, considerable debate exists over whether multiple natural enemies often interact to produce additive or non-additive effects on their prey or host populations. Based on the large data set stored in the Sao Joao and Barra sugarcane mills (state of São Paulo, Brazil) regarding the programme of biological control of Diatraea saccharalis using the parasitoids Cotesia flavipes and tachinid flies, in the present study the author investigated whether the parasitoids released into sugarcane fields interfered significantly with the rate of parasitized D. saccharalis hosts. The author also observed whether there was an additive effect of releasing C. flavipes and tachinids on the rate of parasitized hosts, and looked for evidence of possible negative effects of the use of multiple parasitoid species in this biological control programme. Results showed that C. flavipes and the tachinids were concomitantly released in the Barra Mill, but not in the Sao Jao Mill. Furthermore, in the Barra Mill there was evidence that the parasitoids interacted because the percentage of parasitism did not increase after the release of either C. flavipes or tachinids. In the Sao Joao Mill, when both parasitoid species were released out of synchrony, both the percentage of parasitism by C. flavipes as well as that of the tachinids increased. When large numbers of tachinids were released in the Barra Mill, they caused a significant lower percentage of parasitism imposed by C. flavipes. The implications of the results as evidence of non-additive effects of C. flavipes plus tachinids on D. saccharalis populations are discussed.

Comparação dos padrões de atratividade de Hermetia illucens (Diptera, Stratiomyidae) associada a carcaças de Rattus norvergicus enterradas e tratadas com hormônios esteróides

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Seasonal fecundity and body size in Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

Neste estudo a variação sazonal da fecundidade, tamanhos de asa e tíbia, foi investigada em populações naturais de Chrysomya megacephala (Fabricius) a fim de determinar variações nas características bionômicas da espécie em função da sazonalidade. Uma trajetória temporal relativamente constante foi encontrada para fecundidade, tamanhos de asa e tíbia durante doze meses. Correlações positivas e significativas entre tamanho da asa e temperatura, tamanho da tíbia e temperatura e tamanhos da asa e tíbia foram observadas. As implicações desses resultados para a dinâmica populacional de C. megacephala foram discutidas.

Seasonal population dynamics in Lucilia eximia (Wiedemann) (Diptera: Calliphoridae)

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