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1.  Correction: Olfactory Cues Are Subordinate to Visual Stimuli in a Neotropical Generalist Weevil 
PLoS ONE  2013;8(9):10.1371/annotation/82488be5-8e90-4f03-97f4-5e1822b5623d.
PMCID: PMC3779275
2.  Olfactory Cues Are Subordinate to Visual Stimuli in a Neotropical Generalist Weevil 
PLoS ONE  2013;8(1):e53120.
The tropical root weevil Diaprepes abbreviatus is a major pest of multiple crops in the Caribbean Islands and has become a serious constraint to citrus production in the United States. Recent work has identified host and conspecific volatiles that mediate host- and mate-finding by D. abbreviatus. The interaction of light, color, and odors has not been studied in this species. The responses of male and female D. abbreviatus to narrow bandwidths of visible light emitted by LEDs offered alone and in combination with olfactory stimuli were studied in a specially-designed multiple choice arena combined with a locomotion compensator. Weevils were more attracted to wavelengths close to green and yellow compared with blue or ultraviolet, but preferred red and darkness over green. Additionally, dim green light was preferred over brighter green. Adult weevils were also attracted to the odor of its citrus host + conspecifics. However, the attractiveness of citrus + conspecific odors disappeared in the presence of a green light. Photic stimulation induced males but not females to increase their speed. In the presence of light emitted by LEDs, turning speed decreased and path straightness increased, indicating that weevils tended to walk less tortuously. Diaprepes abbreviatus showed a hierarchy between chemo- and photo-taxis in the series of experiments presented herein, where the presence of the green light abolished upwind anemotaxis elicited by the pheromone + host plant odor. Insight into the strong responses to visual stimuli of chemically stimulated insects may be provided when the amount of information supplied by vision and olfaction is compared, as the information transmission capacity of compound eyes is estimated to be several orders of magnitude higher compared with the olfactory system. Subordination of olfactory responses by photic stimuli should be considered in the design of strategies aimed at management of such insects.
PMCID: PMC3547024  PMID: 23341926
3.  Identification and Synthesis of a Male-Produced Pheromone for the Neotropical Root Weevil Diaprepes abbreviatus 
Journal of Chemical Ecology  2012;38(4):408-417.
An unsaturated hydroxy-ester pheromone was isolated from the headspace and feces of male Diaprepes abbreviatus, identified, and synthesized. The pheromone, methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate, was discovered by gas chromatography-coupled electroantennogram detection (GC-EAD), and identified by gas chromatography–mass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The synthesis yielded an 86:14 mixture of methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate (active) and methyl (Z)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate (inactive), along with a lactone breakdown product. The activity of the synthetic E-isomer was confirmed by GC-EAD, GC-MS, NMR, and bioassays. No antennal response was observed to the Z-isomer or the lactone. In a two-choice olfactometer bioassay, female D. abbreviatus moved upwind towards the synthetic pheromone or natural pheromone more often compared with clean air. Males showed no clear preference for the synthetic pheromone. This pheromone, alone or in combination with plant volatiles, may play a role in the location of males by female D. abbreviatus.
Electronic supplementary material
The online version of this article (doi:10.1007/s10886-012-0096-8) contains supplementary material, which is available to authorized users.
PMCID: PMC3324679  PMID: 22434385
Citrus root weevil; Pheromone; GC-EAD; Methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate; Coleoptera; Curculionidae; Crop pest
4.  Multimodal Stimulation of Colorado Potato Beetle Reveals Modulation of Pheromone Response by Yellow Light 
PLoS ONE  2011;6(6):e20990.
Orientation of insects to host plants and conspecifics is the result of detection and integration of chemical and physical cues present in the environment. Sensory organs have evolved to be sensitive to important signals, providing neural input for higher order multimodal processing and behavioral output. Here we report experiments to determine decisions made by Colorado potato beetle (CPB), Leptinotarsa decemlineata, in response to isolated stimuli and multimodal combinations of signals on a locomotion compensator. Our results show that in complete darkness and in the absence of other stimuli, pheromonal stimulation increases attraction behavior of CPB as measured in oriented displacement and walking speed. However, orientation to the pheromone is abolished when presented with the alternative stimulation of a low intensity yellow light in a dark environment. The ability of the pheromone to stimulate these diurnal beetles in the dark in the absence of other stimuli is an unexpected but interesting observation. The predominance of the phototactic response over that to pheromone when low intensity lights were offered as choices seems to confirm the diurnal nature of the insect. The biological significance of the response to pheromone in the dark is unclear. The phototactic response will play a key role in elucidating multimodal stimulation in the host-finding process of CPB, and perhaps other insects. Such information might be exploited in the design of applications to attract and trap CPB for survey or control purposes and other insect pests using similar orientation mechanisms.
PMCID: PMC3112223  PMID: 21695167
5.  Water-seeking behavior in worm-infected crickets and reversibility of parasitic manipulation 
Behavioral Ecology  2011;22(2):392-400.
One of the most fascinating examples of parasite-induced host manipulation is that of hairworms, first, because they induce a spectacular “suicide” water-seeking behavior in their terrestrial insect hosts and, second, because the emergence of the parasite is not lethal per se for the host that can live several months following parasite release. The mechanisms hairworms use to increase the encounter rate between their host and water remain, however, poorly understood. Considering the selective landscape in which nematomorph manipulation has evolved as well as previously obtained proteomics data, we predicted that crickets harboring mature hairworms would display a modified behavioral response to light. Since following parasite emergence in water, the cricket host and parasitic worm do not interact physiologically anymore, we also predicted that the host would recover from the modified behaviors. We examined the effect of hairworm infection on different behavioral responses of the host when stimulated by light to record responses from uninfected, infected, and ex-infected crickets. We showed that hairworm infection fundamentally modifies cricket behavior by inducing directed responses to light, a condition from which they mostly recover once the parasite is released. This study supports the idea that host manipulation by parasites is subtle, complex, and multidimensional.
PMCID: PMC3071748  PMID: 22476265
behavior; insects; nematomorph; parasite manipulation; parasitism; phototaxis

Results 1-5 (5)