Olfactory cues play important roles in the lives of insects, providing information about biologically relevant resources such as food, mates, and oviposition sites. Moths are among the most economically significant agricultural pests, but an understanding of the sensory cues controlling oviposition choice in adult moths is lacking. This study utilizes an experimentally favorable moth (the giant moth Manduca sexta) to advance the understanding of the behavioral control of oviposition and the olfactory cues that may lead to progress in pest control. This project will investigate the neural mechanisms that allow this specialist insect to evaluate appropriate plants for oviposition. Using a mutualistic system between the hostplant, Datura wrightii, and its primary pollinator and larval host, Manduca sexta, will allow inference about adaptive behavior and function of olfactory systems in general. This project encompasses three levels of analysis: behavioral, neurophysiological, and chemical. First, the host plant odors mediating attraction and repellence for oviposition will be analyzed. Second, neural responses of olfactory neurons in the brain of moths to stimulation with the hostplant odors and the chemical constituents within the odors will be studied. This will reveal specific odor compounds that activate neural pathways controlling oviposition behavior. As a final step, these bio-active volatile compounds will be tested in behavioral oviposition experiments. To strengthen the societal relevance of our research and broaden its impact, we will: (1) involve undergraduate students in multidisciplinary basic research; (2) increase participation of minority students and women in biological science and enrollment in baccalaureate degree programs; (3) foster faculty and student interaction between a Community College and a Ph.D.-granting university; (4) provide educational outreach in science for students at several levels of K-16 education; (5) commit to translational research in a broader sense, owing to the impacts of insects on human health and welfare.
. Olfactory cues play decisive roles in the lives of most insect species, providing information about relevant resources such as food, mates, and oviposition sites. Moths are among the most economically significant agricultural pests, but understanding of the sensory cues controlling oviposition choice in adult moths is lacking. This study utilizes an experimentally favorable moth (the giant moth Manduca sexta) to advance understanding of the behavioral control of oviposition and the olfactory cues that may lead to progress in pest control. This project investigates the neural mechanisms that allow this specialist insect to evaluate appropriate plants for oviposition, using a multidisciplinary approach that combines behavior, chemistry and neural studies. We first investigated the host-plant odors mediating attraction and repellence for oviposition. Females of M. sexta prefer to oviposit in Solanaceous plants such as tomato, bell peppers, tobacco and jimsonweeds. In addition to mediate feeding, we found in field and laboratory experiments that flower odors of one species with which M. sexta has a benefitial association (the jimsonweed Datura wrightii) produced oviposition attraction. Using chemical ecology methods, we identified the volatiles within the floral odor that mediate this attraction. We found a specific odorant within the floral odor that is indeed processed in a female-specific structure in the moth brain, and therefore, likely controls oviposition. Because plants respond to herbivory by releasing volatiles that attract the natural enemies of herbivores, we hypothesized that females should avoid ovipositing on those plants because they are likely to host competitors of their offspring, and to attract parasitoids that would attack their offspring. Indeed we found that females avoided ovipositing in larva-damaged plants of several host-plant species. Chemical analyses showed differences in the vegetative odors released by damaged plants of different plant species, which may explain the differences observed in the oviposition behavior of females. We also examined changes in nectar floral chemistry in larva-damaged plants. Depending on the plant species, we found changes in the alkaloid and sugar content in larva-damaged plants, which affected pollinator visitation time. Finally, we examined the responses of olfactory neurons in the moth brain to stimulation with odors collected from intact and larva-damaged plants, a technique which allowed us to identify important bioactive components. We found that the odors released by intact plants are not only different from those released by larva-damaged plants, but they also elicited differential responses in the female’s primary olfactory centers of the brain. Neurons showed strong responses to monoterpenoid odor compounds such as myrcene, sabinene, and α-pinene, 3-hexanol and linalool. Overall, these experiments suggest that the oviposition behavior of females results from an evaluation of attractive and repellent cues, and that specific odor compounds likely activate neural pathways controlling oviposition behavior. This award provided support for two new investigators and provided research opportunities for several undergraduate students, whom were involved in designing, preparing and conducting experiments. We organized and participated in outreach activities organized on the University of Arizona campus with the participation of kids age 2-14. In this activity kids have exposure to science activities, with emphasis in insect behavior, insect-plant interactions, a portable set up for electrophysiological recordings, handling of insects, etc… Each year more than 70 kids attended this activity during a 4-hour period. We also imparted an annual class to school teachers from Central America which are studying on USA (at the University of Arizona) to improve their science education curricula. We also conducted an educational activity with second grade students in collaboration with their teacher. During a 3-week period, students were assigned relatively simple science projects that involve observation of insect growth, hatching, measurements, use of different plant species, and data recording. At the end of the 3-week period, the class discussed the results in a "mini-conference", to exemplify the process of scientific research. Thus, this project not only provided new knowledge that should lead to improvement of human health and welfare through enhanced management of harmful insects, but also contributed to the science education of elementary-school students, and provided research experience for undergraduate students.
