957 resultados para predator-prey interaction
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Clustering of alphavbeta3 integrin after interaction with the RGD-like integrin-binding sequence present in neuronal Thy-1 triggers formation of focal adhesions and stress fibers in astrocytes via RhoA activation. A putative heparin-binding domain is present in Thy-1, raising the possibility that this membrane protein stimulates astrocyte adhesion via engagement of an integrin and the proteoglycan syndecan-4. Indeed, heparin, heparitinase treatment and mutation of the Thy-1 heparin-binding site each inhibited Thy-1-induced RhoA activation, as well as formation of focal adhesions and stress fibers in DI TNC(1) astrocytes. These responses required both syndecan-4 binding and signaling, as evidenced by silencing syndecan-4 expression and by overexpressing a syndecan-4 mutant lacking the intracellular domain, respectively. Furthermore, lack of RhoA activation and astrocyte responses in the presence of a PKC inhibitor or a dominant-negative form of PKCalpha implicated PKCalpha and RhoA activation in these events. Therefore, combined interaction of the astrocyte alphavbeta3-integrin-syndecan-4 receptor pair with Thy-1, promotes adhesion to the underlying matrix via PKCalpha- and RhoA-dependent pathways. Importantly, signaling events triggered by such receptor cooperation are shown here to be the consequence of cell-cell rather than cell-matrix interactions. These observations are likely to be of widespread biological relevance because Thy-1-integrin binding is reportedly relevant to melanoma invasion, monocyte transmigration through endothelial cells and host defense mechanisms.
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Studies aiming at explaining specialization along latitudinal gradients of plant-herbivore interactions have, to date, yielded inconclusive results. Here we propose the use of steep altitudinal gradients for dissecting factors driving evolution of polyphagy in insect herbivores. First, we test whether colonization of high elevation environment favours increased niche-breadth in two disparate insect groups - the wood-boring beetles and the pollinator group of bees - and show increased polyphagy at higher altitudes in both groups. We then assess classic assumptions transferred from the 'latitude-niche-breadth hypothesis', particularly the increase in environmental variability at high, compared to low, altitude. Finally, we discuss alternative mechanisms shaping the observed pattern of increased polyphagy in altitude, including variation in plant quality and predator pressure at different altitudes. We thus suggest evidence for the 'altitude niche-breadth hypothesis', in which both abiotic and biotic conditions, including increased variability and an increase of the potential feeding niche-breadth, promote evolution for increased insect polyphagy in altitude.
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The paper deals with the comparative study of European citizens satisfaction with thestate of education in their respective countries. Individual and contextual effects aretested applying multilevel analysis. The results show that educational public policies(level of decentralization, degree of comprehensiveness and public spending) as well asthe students social environment (socioeconomic and cultural status) have a soundimpact on the opinions about the state of education.
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Interaction betweeen Telenomus remus and Trichogramma pretiosum in the management of Spodoptera spp. The use of egg parasitoids is a promising strategy for Integrated Pest Management (IPM), but different species of parasitoids have greater or lesser control efficiency, depending on the pest species. Recently, not only Anticarsia gemmatalis and Pseudoplusia includens but also Spodoptera cosmioides and S. eridania have been among the key Lepidoptera larvae attacking soybeans. This study evaluated the combination of Telenomus remus and Trichogramma pretiosum for parasitism of eggs of the Spodoptera complex, for better control efficiency and broader spectrum of action among the key pests of soybeans. The experiment was carried out under controlled environmental conditions (25 ± 2ºC; 70 ± 10% RH; and 14 h photophase) in a completely randomized experimental design with seven treatments and 10 replicates with S. frugiperda, S. cosmioides and S. eridania eggs. Each replicate consisted of one egg mass of each Spodoptera species, with approximately 100 eggs offered to the parasitoids. The treatments were: 1) 10 females of T. pretiosum; 2) nine females of T. pretiosum and one female of T. remus; 3) eight females of T. pretiosum and two females of T. remus; 4) seven females of T. pretiosum and three females of T. remus; 5) six females of T. pretiosum and four females of T. remus; 6) five females of T. pretiosum and five females of T. remus, and 7) 10 females of T. remus. The parameter evaluated was the percentage of parasitized eggs. Results showed that treatments combining both parasitoid species with only 1 T. remus for each 9 T. pretiosum (10%) and only 2 T. remus for each 8 T. pretiosum (20%) were enough to significantly increase the parasitism observed on eggs of S. cosmioides and S. frugiperda, respectively. This association of T. pretiosum and T. remus in different proportions is very promising for biological control in IPM programs because it provides wide spectrum of control.
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Effect of gossypol on survival and reproduction of the zoophytophagous stinkbug Podisus nigrispinus (Dallas). Gossypol is a sesquiterpene aldehyde found in cotton plants conferring resistance against herbivory. Although the effect of this sesquiterpenoid on insect pests of cotton is known, the interaction of this compound with zoophytophagous predators such as Podisus nigrispinus (Dallas) (Hemiptera, Pentatomidae) has not been studied so far. Thus, the objective of this study was to evaluate the effect of the purified gossypol on nymphs and adults of P. nigrispinus. Nymphs and adults of this predator were fed on Tenebrio molitor pupae and supplemented with solutions of gossypol at concentrations of 0.00, 0.05, 0.10, and 0.20% (w/v) during the nymphal and adult stages or, only during the adult stage of P. nigrispinus. The nymphal stage of the predator was, on average, two days longer when suplemmented with gossypol. Emerged adults had lower fecundity and egg hatching, especially at the highest gossypol concentration (0.20%) ingested during the nymphal and adult stages. However, this predator was not affected when it ingested the compound only during the adult stage. P. nigrispinus can have delayed nymphal development and lower reproductive performance when ingesting the gossypol during the nymphal and adult stages, but only at higher concentrations of gossypol than that produced by cotton plants.
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BACKGROUND: The magnitude of risk conferred by the interaction between tobacco and alcohol use on the risk of head and neck cancers is not clear because studies have used various methods to quantify the excess head and neck cancer burden. METHODS: We analyzed individual-level pooled data from 17 European and American case-control studies (11,221 cases and 16,168 controls) participating in the International Head and Neck Cancer Epidemiology consortium. We estimated the multiplicative interaction parameter (psi) and population attributable risks (PAR). RESULTS: A greater than multiplicative joint effect between ever tobacco and alcohol use was observed for head and neck cancer risk (psi = 2.15; 95% confidence interval, 1.53-3.04). The PAR for tobacco or alcohol was 72% (95% confidence interval, 61-79%) for head and neck cancer, of which 4% was due to alcohol alone, 33% was due to tobacco alone, and 35% was due to tobacco and alcohol combined. The total PAR differed by subsite (64% for oral cavity cancer, 72% for pharyngeal cancer, 89% for laryngeal cancer), by sex (74% for men, 57% for women), by age (33% for cases <45 years, 73% for cases >60 years), and by region (84% in Europe, 51% in North America, 83% in Latin America). CONCLUSIONS: Our results confirm that the joint effect between tobacco and alcohol use is greater than multiplicative on head and neck cancer risk. However, a substantial proportion of head and neck cancers cannot be attributed to tobacco or alcohol use, particularly for oral cavity cancer and for head and neck cancer among women and among young-onset cases.
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Assassin bugs (Reduviidae) are voracious insects that prey on other arthropods. Recent evidences have pointed out that these predators also feed on plant derived substances in rare opportunities. The present study describes the feeding behavior of the reduviid Atopozelus opsimus on extrafloral nectaries of Inga vera (Fabaceae) in a Neotropical savanna area. It was investigated if the insects feed more frequently of extrafloral nectar or prey, and if individuals of different stages of development vary according to feeding behavior. Notably, the results suggest that the diet of all instars and adults consist mainly of extrafloral nectar (N = 1013), in detriment of captured prey ingestion (N = 18). Also, there was no variation on feeding behavior and life stage.
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Developmental biology, polymorphism and ecological aspects of Stiretrus decemguttatus (Hemiptera, Pentatomidae), an important predator of cassidine beetles. Stiretrus decemguttatus is an important predator of two species of cassidine beetles, Botanochara sedecimpustulata (Fabricius, 1781) and Zatrephina lineata (Fabricius, 1787) (Coleoptera, Cassidinae), on the Marajó Island, Brazil. It attacks individuals in all development stages, but preys preferentially on late-instar larvae. Its life cycle in the laboratory was 43.70 ± 1.09 days, with an egg incubation period of six days and duration from nymph and adult stages of 16.31 ± 0.11 and 22.10 ± 1.67 days, respectively. The duration of one generation (T) was 12.65 days and the intrinsic population growth rate (r) 0.25. These data reveal the adjustment of the life cycle of S. decemgutattus with those of the two preys, but suggest greater impact on Z. lineata. However, no preference over cassidine species was shown in the laboratory. Up to 17 different color patterns can be found in adults of S. decemguttatus, based on combinations of three basic sets of color markings. Some of them resemble the markings of chrysomelids associated with Ipomoea asarifolia (Convolvulaceae) and are possibly a mimetic ring. Three color patterns were identified in nymphs, none of which was associated with any specific adult color pattern.
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Prey identification in nests of the potter wasp Hypodynerus andeus (Packard) (Hymenoptera, Vespidae, Eumeninae) using DNA barcodes. Geometrid larvae are the only prey known for larvae of the Neotropical potter wasp Hypodynerus andeus (Packard, 1869) (Hymenoptera, Vespidae, Eumeninae) in the coastal valleys of the northern Chilean Atacama Desert. A fragment of the mitochondrial gene cytochrome oxidase c subunit 1 was amplified from geometrid larvae collected from cells of H. andeus in the Azapa Valley, Arica Province, and used to provide taxonomic identifications. Two species, Iridopsis hausmanni Vargas, 2007 and Macaria mirthae Vargas, Parra & Hausmann, 2005 were identified, while three others could be identified only at higher taxonomic levels, because the barcode reference library of geometrid moths is still incomplete for northern Chile.
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Twenty species of Tephritidae (Diptera) are recorded in association with capitula of plants in the family Asteraceae. The Tephritidae genus Tetreuarestais registered for Rio Grande do Sul for the first time. Five species of Tephritidae are newly recorded for Rio Grande do Sul, and new hosts are recorded for the following fly species: Dioxyna chilensis (Macquart), Plaumannimyia dolores (Hering), Plaumannimyia imitatrix (Hering), Plaumannimyia miseta(Hering), Plaumannimyia pallensHering, Tomoplagia incompleta (Williston), Tomoplagia matzenbacheriPrado, Norrbom & Lewinsohn, Tomoplagia reimoseriHendel, Xanthaciura biocellata(Thomson) and Xanthaciura chrysura(Thomson).
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Doctoral dissertation, University of Turku