Neuroethology of olfactory-guided behavior and its potential application in the control of harmful insects

Harmful insects include pests of crops and storage goods, and vectors of human and animal diseases. Throughout their history, humans have been fighting them using diverse methods. The fairly recent development of synthetic chemical insecticides promised efficient crop and health protection at a relatively low cost. However, the negative effects of those insecticides on human health and the environment, as well as the development of insect resistance, have been fueling the search for alternative control tools. New and promising alternative methods to fight harmful insects include the manipulation of their behavior using synthetic versions of "semiochemicals", which are natural volatile and non-volatile substances involved in the intra-and/or inter-specific communication between organisms. Synthetic semiochemicals can be used as trap baits to monitor the presence of insects, so that insecticide spraying can be planned rationally (i.e., only when and where insects are actually present). Other methods that use semiochemicals include insect annihilation by mass trapping, attract-and-kill techniques, behavioral disruption, and the use of repellents. In the last decades many investigations focused on the neural bases of insect's responses to semiochemicals. Those studies help understand how the olfactory system detects and processes information about odors, which could lead to the design of efficient control tools, including odor baits, repellents or ways to confound insects. Here we review our current knowledge about the neural mechanisms controlling olfactory responses to semiochemicals in harmful insects. We also discuss how this neuroethology approach can be used to design or improve pest/vector management strategies.Fil: Reisenman, Carolina Esther. University of California at Berkeley; Estados UnidosFil: Lei, Hong. University of Arizona; Estados UnidosFil: Guerenstein, Pablo Gustavo. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; Argentin

Feeding and defecation behavior of Triatoma rubida (Uhler, 1894) (Hemiptera: Reduviidae) under laboratory conditions, and its potential role as a vector of chagas disease in Arizona, USA

Chagas disease is caused by the parasite Trypanosoma cruzi, which is transmitted to humans by blood-sucking triatomine insects. This disease is endemic throughout Mexico and Central and South America, but only a few autochthonous cases have been reported in the United States, despite the fact that infected insects readily invade houses and feed on humans. Competent vectors defecate during or shortly after feeding so that infective feces contact the host. We thus studied the feeding and defecation behaviors of the prevalent species in southern Arizona, Triatoma rubida. We found that whereas defecation during feeding was frequent in females (93%), it was very rare in immature stages (3%), and absent in males. Furthermore, more than half of the immature insects that exhibited multiple feeding bouts (62%) defecated during interruptions of feeding, i.e., while likely on or near the host. These results indicate that T. rubida potentially could transmit T. cruzi to humans.Fil: Reisenman, Carolina Esther. University of Arizona; Estados UnidosFil: Gregory, Teresa. University of Arizona; Estados UnidosFil: Guerenstein, Pablo Gustavo. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Hildebrand, John. University of Arizona; Estados Unido

Effects of starvation on the olfactory responses of the blood-sucking bug Rhodnius prolixus

Blood-sucking insects use olfactory cues in a variety of behavioral contexts, including host-seeking and aggregation. In triatomines, which are obligated blood-feeders, it has been shown that the response to CO2, a host-associated olfactory cue used almost universally by blood-sucking insects, is modulated by hunger. Host-finding is a particularly dangerous task for these insects, as their hosts are also their potential predators. Here we investigated whether olfactory responses to host-derived volatiles other than CO2 (nonanal, α-pinene and (−)-limonene), attractive odorant mixtures (yeast volatiles), and aggregation pheromones (present in feces) are also modulated by starvation in the blood-sucking bug Rhodnius prolixus. For this, the responses of both non-starved and starved insects were individually tested at the beginning of the scotophase using a dual-choice “T-shaped” olfactometer, in which one of its arms presented odor-laden air and the other arm presented odorless air. We found that the response of non-starved insects toward host-odorants and odorant mixtures was odor-dependent: insects preferred the odor-laden arm of the maze when tested with α-pinene, the odorless arm of the maze when tested with (−)-limonene, and distributed at random when tested with yeast volatiles or nonanal. In contrast, starved insects significantly preferred the odor-laden arm of the maze when tested with host-odorants or yeast volatiles. When tested with aggregation be, while starved insects preferred the odorless arm of the maze; insects that were even more starved (8–9 weeks post-ecdysis) significantly preferred the odor-laden arm of the maze. We postulate that this odor- and starvation-dependent modulation of sensory responses has a high adaptive value, as it minimizes the costs and risks associated with the associated behaviors. The possible physiological mechanisms underlying these modulatory effects are discussed.Fil: Reisenman, Carolina Esther. University of Arizona; Estados UnidosFil: Lee, Yan. University of Arizona; Estados UnidosFil: Gregory, Teresa. University of Arizona; Estados UnidosFil: Guerenstein, Pablo Gustavo. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina. Universidad Nacional de Entre Ríos; Argentin