Chemical cues related to conspecific size in pintado catfish, Pseudoplatystoma coruscans

The pintado (Pseudoplatystoma coruscans) is a ferocious carnivorous catfish with evident cannibalistic behaviour; its nocturnal habits are related to its ability to use predominately chemical sensorial modalities. This study investigated whether the pintado distinguishes conspecifics of different body sizes using chemical cues, which may reflect different physiological conditions such as hunger or stress. Pintados were observed when receiving water conditioned by either larger or similar-size conspecifics. A control group consisted of pintados receiving unconditioned water. Twelve repetitions were used for each condition. Feeding-like behaviours were investigated in the receiver fish and showed that they responded only to the conditioned water. Furthermore, a higher frequency of responses occurred when the water was conditioned by a similar-size conspecific. Thus, it is concluded that pintados are able to recognize conspecific size by chemical cues related to size and that this ability contributes to the individual's decision making on whether to approach or to avoid the conspecific.

Effects of Food Deprivation on the Development of Coleomegilla maculata (De Geer) (Coleoptera: Coccinellidae)

The lady beetle Coleomegilla maculata (De Geer) is a natural enemy of several insect pests and feeds on pollen and nectar to survive periods when prey is scarce. The effect of the feeding interval on the development, survival, fecundity, and longevity of C. maculata was determined. Newly hatched larvae of C. maculata were reared individually and fed with eggs of the Mediterranean flour moth Anagasta kuehniella (Zeller) at intervals of one, two, and three days under controlled conditions (23 ± 1ºC; 60 ± 10% RH; 12 h phtophase). The duration of larval instars and the total larval stage was prolonged as the feeding interval increased. The larval period lasted on average 9.2 ± 0.19 days when the larvae were fed daily with prey, and 14.6 ± 0.48 days when food was offered at three-day intervals. There was an inverse relationship between food intervals, survival, and weight of larvae and adults of the coccinellid. Survival rate of larvae fed daily was 76.8%, while the rate was 50.0% and 23.4% for larvae fed every two and three days, respectively. Coleomegilla maculata showed fecundity of 781.1 ± 149.02, 563.4 ± 80.81 and 109.0 ± 103.0 eggs when fed daily and at intervals of two and three days, respectively.

Consequences of refuge for the functional response of Dermestes ater (Coleoptera : Dermestidae) to Musca domestica (Diptera : Muscidae)

It is well known that a predator has the potential to regulate a prey population only if the predator responds to increases in prey density and inflicts greater mortality rates. Predators may cause such density-dependent mortality depending on the nature of the functional and numerical responses. Yet, few studies have examined the relationship between the addition of refuges and the characteristic of functional response fits. We investigated whether addition of a refuge changed the type of functional response exhibited by Dermestes ater on Musca domestica, comparing the inherent ability of D. ater to kill houseflies in the absence and in the presence of refuge. An additional laboratory experiment was also carried out to assess handling and searching times exhibited by D. ater. Logistic regression analyses revealed a type III functional response for predator-prey interaction without refuge, and results were described by the random predator equation. The mean number of prey killed did not differ between experimental habitats, indicating that the addition of refuge did not inhibit predation. However, predators that interacted with prey without refuge spent less time searching for prey at higher densities, increasing predatory interaction. We concluded that this interaction may be weak, because data from experiments with refuge fitted poorly to models. However, the high variability and the nonsignificance of the data from the experiment with refuge show the importance of refuge for promoting spatial heterogeneity, which may prevent prey extinction.

PREDATION OF COTTON LEAFWORM 1ST INSTAR LARVAE, ALABAMA-ARGILLACEA [LEP, NOCTUIDAE]

Natural predation first instar larvae of the cotton leafworm (CLW) A. argillacea was studied in cotton fields in Jaboticabal, São Paulo State, Brazil, during 1986. The presence of naturally occurring arthropod predators showed a first instar larvae predation rate of 78.6 and 88.9% after 24 h and 48 h of exposure, respectively. A predator prey ratio of 1 : 1 (1 CLW key predator per 1 prey/plant) maintained a level of no more than 1 CLW small larvae per plant. The most evident arthropod predators in the studied fields were: beetles (Coleoptera: Coccinellidae), ants Pheidole sp. and Conomyrma sp.; Dermaptera Doru lineare (Eschs); Hemiptera Geocoris sp., and Orius insidiosus Say; and the spiders Theridion volubile, Chrysso pulcherrima, Misumenops sp., Chiracanthium sp., and Oxyopes salticus Hentz.

The ecological causes of individual specialisation

University of Tennessee, KnoxvilleNational Science Foundation (NSF)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Management of vomplex systems: Modeling the biological pest control

The aim of this paper is to study the cropping system as complex one, applying methods from theory of dynamic systems and from the control theory to the mathematical modeling of the biological pest control. The complex system can be described by different mathematical models. Based on three models of the pest control, the various scenarios have been simulated in order to obtain the pest control strategy only through natural enemies' introduction. © 2008 World Scientific Publishing Company.

Efeito da heterogeneidade ambiental na predação de girinos de Scinax fuscovarius e Physalaemus cuvieri por larvas de Odonata

The objective of this work were to analyze the effect of predation by Odonata naiads on two amphibian species with distinct habits - benthic and mid-water -and to verify whether the presence and architecture of macrophytes can mediate this interaction. All tadpoles and Odonata larvae were captured in a temporary pond. Sixteen tanks were used for three different treatments: Pistia, Salvinia and no macrophytes. Ten tadpoles of each species and two Odonata larvae were placed in each tank. The survival of tadpoles according to treatments was assessed through analysis of repeated measures. We concluded that the survival of P. cuvieri and S. fuscovarius tadpoles was not affected by the presence and architecture of the macrophytes (Pistia and Salvinia) or by their behavior.

Uso de recursos e padrão de co-ocorrência com insetos predadores em comunidades sub-tropicais de girinos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento e aplicação de modelos matemáticos para o controle da Diaphorina citri via manejo integrado e estudo da influência da temperatura sobre a dinâmica populacional de Talitroides topitotum

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estabilidade global e bifurcação de Hopf em um modelo de HIV baseado em sistemas do tipo Lotka-Volterra

Pós-graduação em Matematica Aplicada e Computacional - FCT

Teoria de estabilidade de equações diferenciais ordinárias e aplicações: modelos presa-predador e competição entre espécies

Pós-graduação em Matemática Universitária - IGCE

Caracterização biológico-comportamental de Podisus nigrispinus (Dallas, 1851) predando Plutella xylostella (L., 1758)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Recursos através dos ecossistemas: insetos aquáticos emergentes subsidiam comunidade de aranhas ripárias

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

Effect of tank colour on larval performance of the Amazon River prawn Macrobrachium amazonicum

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Modelo de Lotka-Volterra com inclusão de termos perturbativos e capacitivos

Our purpose is to show the effects in the predator-prey trajectories due to parameter temporal perturbations and/or inclusion of capacitive terms in the Lotka Volterra Model. An introduction to the Lotka Volterra Model (chapter 2) required a brief review of nonlinear differential equations and stability analysis (chapter 1) , for a better understanding of our work. In the following chapters we display in sequence our results and discussion for the randomic pertubation case (chapter 3); periodic perturbation (chapter 4) and inclusion of capacitive terms (chapter 5). Finally (chapter 6) we synthesize our result