29 resultados para prey-predator demography


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First observation of alternative food usage (extrafloral nectar) by the assassin bug Atopozelus opsimus (Hemiptera, Reduviidae). 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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The objective of this work was to evaluate the toxicity of synthetic and natural compounds on Tetranychus urticae and the predator Phytoseiulus macropilis. Mortality and growth rates of T. urticae and its predator were evaluated after applications of: abamectin, clofentezine, fenpropathrin, fenpyroximate, propargite, sulfur and spiromesifen, at their recommended concentrations; neem oils (Natuneem and Sempre Verde Killer Neem at 1%); and aqueous extracts at 10% of Dieffenbachia brasiliensis, Annona squamosa, Ruta graveolens, Agave angustifolia, Melia azedarach, Sonchus oleraceus, Mentha spicata x M. suaveolens, Allium cepa, Laurus nobilis, and Eucalyptus saligna. The acute toxicity and the influence of the compounds on the instantaneous growth rate of the mites were carried out in laboratory. Extracts of A. cepa, A. angustifolia, neem oil-based products, spiromesifen, propargite, fenpyroximate, abamectin and fenpropathrin caused mortality higher than 83% on T. urticae. Extract of A. angustifolia, Natuneem and clofentezine did not cause significant mortality rates on P. macropilis. Agave angustifolia and Natuneem did not affect significantly the growth rate of this predator. Propargite, fenpyroximate, abamectin, fenpropathrin, spiromesifen and extract of L. nobilis severely affected P. macropilis population.

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SECONDARY METABOLITES FROM NUDIBRANCHS Tambja stegosauriformis, Hypselodoris lajenis AND Okenia zoobotryon AND FROM BRYOZOANS Zoobotryon verticillatum AND Bugula dentata FROM THE BRAZILIAN COASTLINE. The chemical investigation of the MeOH extract from the bryozoan B. dentata MeOH yielded tambjamines A (1), C (3), D (4), K (6), aldehyde 8 and the new tambjamine J1(9), while the extract of its predator, the nudibranch Tambja stegosauriformis, yielded tambjamines C and K, along with aldehyde 8. Furodisinin lactone (11) was isolated from the nudibranch Hypselodoris lajensis, a compound previously isolated from Dysidea sponges. The alkaloid 2,5,6-tribromo-N-methylgramine (12) was isolated from the nudibranch Okenia zoobotryon and from its prey, the bryozoan Zoobotryon verticillatum, the only source of 12 previously known.

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Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We examined how variation in strengths of interactions can be described hierarchically, and how this variation impacts the structure of species interactions in predator-prey networks, both of which are important components of ecological food webs. The stable isotope ratios of predator and prey species may be particularly useful for quantifying this variability, and we show how these data can be used to build probabilistic predator-prey networks. Moreover, the distribution of variation in strengths among interactions can be estimated from a limited number of observations. This distribution informs network structure, especially the key role of dietary specialization, which may be useful for predicting structural properties in systems that are difficult to observe. Finally, using three mammalian predator-prey networks ( two African and one Canadian) quantified from stable isotope data, we show that exclusion of link-strength variability results in biased estimates of nestedness and modularity within food webs, whereas the inclusion of body size constraints only marginally increases the predictive accuracy of the isotope-based network. We find that modularity is the consequence of strong link-strengths in both African systems, while nestedness is not significantly present in any of the three predator-prey networks.

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This paper addresses the importance of life cycle aspects in explaining the evolution of regional income inequality. The analysis of household microdata organized in age cohorts shows that Brazilian regional income inequality has different dynamics across generations, with income convergence being observed only for the older generations. The larger income share of younger generations produces a low speed of convergence in the country. When retirement payments, pensions, and other government transfers are excluded from income, convergence is not observed even for the older generations.

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In the present study, the polycyclic aromatic hydrocarbon (PAH) genotoxicity was investigated in a one-step predator-prey relationship with the trophic-related marine species. Florida pompanos were fed for 5 and 10 days with pink shrimp post larvae previously exposed to benzo(a)pyrene (BaP) concentrations. Parent BaP body burden was measured in samples of Farfantepenaeus brasiliensis. BaP metabolites were determined in bile samples of Trachinotus carolinus and DNA damage was assessed through the comet and erythrocyte nuclear abnormalities (ENAs) assays in fish erythrocytes. BaP body burden increased significantly with the PAH concentration in pink shrimp PLs as well as the fish bile BaP metabolites. Both, comet and ENAs assays indicated significant increase on erythrocyte DNA damage of Florida pompanos fed with BaP-exposed pink shrimp on both feeding periods. The trophic route of BaP genotoxicity is discussed as well as the PAH biotransformation as the inducing mechanism for the DNA damages observed.

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The blattisociid mite Lasioseius floridensis Berlese was found associated with the broad mite, Polyphagotarsonemus latus (Banks), on gerbera leaves in Mogi das Cruzes, State of Sao Paulo, Brazil. Blattisociid mites are not common on aerial plant parts, except under high air humidity levels. Some Lasioseius species have been mentioned as effective control agents of rice pest mites, but nothing is known about the biology of L. floridensis. The objective of this study was to evaluate whether the observed co-occurrence of L. floridensis and P. latus was just occasional or whether the latter could be important as food source for the former, assumed by laboratory evaluation of the ability of the predator to maintain itself, reproduce and develop on that prey. Biological parameters of L. floridensis were compared when exposed to P. latus and to other items as food. The study showed that mating is a pre-requisite for L. floridensis to oviposit and that oviposition rate was much higher on the soil nematode Rhabditella axei (Cobbold) (Rhabditidae) than on P. latus. Ovipositon on the acarid mite Tyrophagus putrescentiae (Schrank) was about the same as on P. latus, but it was nearly zero when the predator was fed the fungi Aspergillus flavus Link or Penicillium sp., or cattail (Typha sp.) pollen. Survivorship was higher in the presence of pollen and lower in the presence of A. flavus or Penicillium sp. than in the absence of those types of food. Life table parameters indicated that the predator performed much better on R. axei than on P. latus. To evaluate the potential effect of L. floridensis as predator of P. latus, complementary studies are warranted to determine the frequency of migration of L. floridensis to aerial plant parts, when predation on P. latus could occur.

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Several predatory mites have been found in association with the coconut mite, Aceria guerreronis Keifer, in northeast Brazil. However, the latter still causes damage to coconut in that region. The objectives of this work were to compare the frequencies of occurrence of Neoseiulus (Phytoseiidae) and Proctolaelaps (Melicharidae) species on standing and aborted coconuts in coastal Pernambuco State, northeast Brazil and to analyze their possible limitations as control agents of the coconut mite, based on evaluations of the restrictions they may have to access the microhabitat inhabited by the pest and their functional and reproductive responses to increasing densities of the latter. Neoseiulus baraki (Athias-Henriot) was found mostly on standing coconuts whereas Proctolaelaps bickleyi (Bram) was found mostly on aborted coconuts. Measurements of the entrance to the microhabitat occupied by the coconut mite, between the bracts and the subjacent fruit surface, showed that this different pattern of predator prevalence could be related to predator sizes, although other environmental factors could not be disregarded. Progressively higher predation rate of N. baraki was observed up to an experimental density that corresponded to 1,200 coconut mites per fruit, which is close to the average number determined in northeast Brazil, reducing slightly afterwards. Predation rate of P. bickleyi reduced consistently but slightly with increasing prey densities, but in absolute values, rates were always much higher than determined for N. baraki. The excessively high killing capacity of P. bickleyi, probably related to its high feeding requirement, may be detrimental in terms of stability. In fact, such high requirement for food suggests that P. bickleyi might not have a strong relation with the coconut mite and that the latter may not be its main food source under natural conditions. It is concluded that body sizes of both predators and the exceedingly high feeding requirement of P. bickleyi may limit their performance as control agents of the coconut mite.

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In Ostariophysan fish, the detection of the alarm substance liberated into the water as a consequence of an attack by a predator elicits an alarm reaction or anti-predatory behavior. In this study, experiments were performed to: (i) describe and quantitatively characterize the behavioral and ventilatory responses in piaucu fish (Leporinus macrocephalus), individually and as part of a school, to conspecific alarm substance (CAS) and; (ii) test the effect of acute fluoxetine treatment on alarm reaction. Histological analysis revealed the presence of club cells in the intermediate and superficial layers of the epidermis. The predominant behavioral response to CAS was freezing for fish held individually, characterized by the cessation of the swimming activity as the animal settles to a bottom corner of the aquarium. Fish exposed to CAS showed decrease in the mean ventilatory frequency (approximately 13%) relative to control. In schools, CAS elicited a biphasic response that was characterized by erratic movements followed by increased school cohesion and immobility, reflected as an increased school cohesion (65.5% vs. -5.8% for controls) and in the number of animals near the bottom of the aquarium (42.0% vs. 6.5% for controls). Animals treated with single i.p. injections of fluoxetine (10 mu g/g b.w.) did not exhibit alarm behavior following CAS stimulation. These results show that an alarm pheromone system is present in piaucu fish, evidenced by the presence of epidermal club cells and an alarm reaction induced by CAS and consequently of a chemosensory system to transmit the appropriate information to neural structures responsible for initiating anti-predator behavioral responses. In addition, fluoxetine treatment caused an anxiolytic-like effect following CAS exposure. Thus, the alarm reaction in piaucu can be a useful model for neuroethological and pharmacological studies of anxiety-related states. (C) 2011 Elsevier Inc. All rights reserved.

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Posttraumatic stress disorder (PTSD) is an incapacitating syndrome that follows a traumatic experience. Predator exposure promotes long-lasting anxiogenic effect in rodents, an effect related to symptoms found in PTSD patients. Cannabidiol (CBD) is a non-psychotomimetic component of Cannabis sativa with anxiolytic effects. The present study investigated the anti-anxiety actions of CBD administration in a model of PTSD. Male Wistar rats exposed to a predator (cat) received, 1 h later, singled or repeated i.p. administration of vehicle or CBD. Seven days after the stress animals were submitted to the elevated plus maze. To investigate the involvement of 5HT1A receptors in CBD effects animals were pre-treated with WAY100635, a 5HT1A receptor antagonist. To explore possible neurobiological mechanisms involved in these effects, 5HT1A receptor mRNA and BDNF protein expression were measured in the hippocampus, frontal cortex, amygdaloid complex and dorsal periaqueductal gray. Repeated administration of CBD prevented long-lasting anxiogenic effects promoted by a single predator exposure. Pretreatment with WAY100635 attenuated CBD effects. Seven days after predator exposure 5HT1A mRNA expression was up regulated in the frontal cortex and hippocampus. CBD and paroxetine failed to prevent this effect. No change in BDNF expression was found. In conclusion, predator exposure promotes long-lasting up-regulation of 5HT1A receptor gene expression in the hippocampus and frontal cortex. Repeated CBD administration prevents the long-lasting anxiogenic effects observed after predator exposure probably by facilitating 5HT1A receptors neurotransmission. Our results suggest that CBD has beneficial potential for PTSD treatment and that 5HT1A receptors could be a therapeutic target in this disorder. (C) 2012 Elsevier Ltd. All rights reserved.

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The ventilation rate (VR) of an ostariophysan fish, the speckled catfish Pseudoplaty - stoma coruscans, exposed to a chemical alarm cue was measured in the present study in multiple contexts. The influence of the extraction techniques, skin donor food intake and quantity of the alarm cue (skin extract) on this autonomic response was considered. Overall, the catfish VR decreased significantly when exposed to the skin extract (chemical alarm cue) compared with exposure to distilled water (control). No effect of the extraction technique was found. Increasing doses of the skin extract induced a VR reduction of similar magnitude. However, extract obtained from daily-fed fish induced a significant decrease in the VR, whereas extract obtained from foodrestricted fish did not induce any change in the VR. Thus, food intake was associated with the production of a more easily recognizable alarm cue in the speckled catfish. Interestingly, this effect was not related to differences in the number of club cells in the donor catfish epidermis. Dashing, or rapid swimming, a normal component of the alarm response in fish, including this catfish species, was not observed here, and hypoventilation was always associated with no swimming reaction. Together, these results suggest that hypoventilation is a reaction to a chemical alarm cue, likely resulting in improved crypsis, causing the fish to become less easily perceived by a potential predator that usually strikes prey in response to movement.

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The red-belly toads (Melanophryniscus) of southern South America secrete defensive alkaloids from dermal granular glands. To date, all information on Melanophryniscus alkaloids has been obtained by extraction from either skins or whole organisms; however, in other amphibians, tetrodotoxins, samandarines, and bufadienolides have been detected in both skin and other organs, which raise the possibility that lipophilic alkaloids may occur in non-integumentary tissues in Melanophryniscus as well. To test this hypothesis, we studied the distribution of alkaloids in the skin, skeletal muscle, liver, and mature oocytes of the red-belly toad M. simplex from three localities in southern Brazil. Gas chromatography and mass spectrometry of skin extracts from 11 individuals of M. simplex resulted in the detection of 47 alkaloids (including isomers), 9 unclassified and 38 from 12 known structural classes. Each alkaloid that was present in the skin of an individual was also present in the same relative proportion in that individual's skeletal muscle, liver, and oocytes. The most abundant and widely distributed alkaloids were the pumiliotoxins 251D, 267C, and 323A, 5,8-disubstituted indolizidines 207A and 223D, 5,6,8-trisubstituted indolizidine 231B, 3,5-disubstituted pyrrolizidines cis-223B and cis- and trans-251K, and izidine 211C. We report the first record of piperidines in Melanophryniscus, bringing the total number of alkaloid classes detected in this genus to 16. Alkaloid composition differed significantly among the three study sites. The functional significance of defensive chemicals in non-integumentary tissues is unknown.

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Spitting spiders (Scytodidae) have a distinct predatory strategy in which they eject a sticky secretion from their cheliceral fangs to immobilize prey. This behavior could potentially allow the spider not only to avoid defensive secretions but also to bite specific vulnerable spots of a potential prey such as a harvestman. We used an ethogram, a fluxogram and an experiment to analyze the interaction between the harvestman Discocyrtus invalidus Piza 1938 (Arachnida: Opiliones) and the syntopic spider Scytodes globula (Nicolet 1849) (Arachnida: Araneae). These spiders, while readily taking crickets as prey, seldom spat at and never bit the harvestmen, which apparently did not exude repugnatorial secretions. We therefore tested, by clogging the glands and using appropriate controls, whether non-visible amounts of secretions could cause the rejection, but the harvestmen were still refused. This is the first detailed and quantified description of an interaction between a spitting spider and a harvestman. The general conclusions are that S. globula avoids preying on D. invalidus, S. globula behaves differently when attacking harvestmen and crickets and the scent gland secretions of D. invalidus do not play a direct role in this predator-prey interaction.

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The chemical investigation of the MeOH extract from the bryozoan B. dentata MeOH yielded tambjamines A (1), C (3), D (4), K (6), aldehyde 8 and the new tambjamine J1(9), while the extract of its predator, the nudibranch Tambja stegosauriformis, yielded tambjamines C and K, along with aldehyde 8. Furodisinin lactone (11) was isolated from the nudibranch Hypselodoris lajensis, a compound previously isolated from Dysidea sponges. The alkaloid 2,5,6-tribromo-N-methylgramine (12) was isolated from the nudibranch Okenia zoobotryon and from its prey, the bryozoan Zoobotryon verticillatum, the only source of 12 previously known.