Mosquitoes can change their feeding behaviours based on past experiences, such as shifting from biting animals to biting humans or avoiding defensive hosts (Wolff & Riffell 2018
Mosquitoes use a wide range of cues to find a host to feed on, eventually leading to the transmission of pathogens. Among them, olfactory cues (e.g., host-emitted odors, including CO2, and skin volatiles) play a central role in mediating host-seeking behaviors. While mosquito olfaction can be impacted by many factors, such as the physiological state of the insect (e.g., age, reproductive state), the impact of environmental temperature on the olfactory system remains unknown. In this study, we quantified the behavioral responses of Aedes aegypti mosquitoes, vectors of dengue, yellow fever, and Zika viruses, among other pathogens, to host and plant-related odors under different environmental temperatures.
more » « less- Award ID(s):
- 2124777
- NSF-PAR ID:
- 10425423
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Integrative And Comparative Biology
- ISSN:
- 1540-7063
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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J. Exp. Biol. 221 , jeb157131. (doi:10.1242/jeb.157131 )). Dopamine is a critical neuromodulator for insects, allowing flexibility in their feeding preferences, but its role in the primary olfactory centre, the antennal lobe (AL), remains unclear (Vinaugeret al. 2018Curr. Biol. 28 , 333–344.e8. (doi:10.1016/j.cub.2017.12.015 )). It is also unknown whether mosquitoes can learn some odours and not others, or whether different species learn the same odour cues. We assayed aversive olfactory learning in four mosquito species with different host preferences, and found that they differentially learn odours salient to their preferred host. Mosquitoes that prefer humans learned odours found in mammalian skin, but not a flower odour, and a nectar-feeding species only learned a floral odour. Comparing the brains of these four species revealed significantly different innervation patterns in the AL by dopaminergic neurons. Calcium imaging in theAedes aegypti AL and three-dimensional image analyses of dopaminergic innervation show that glomeruli tuned to learnable odours have significantly higher dopaminergic innervation. Changes in dopamine expression in the insect AL may be an evolutionary mechanism to adapt olfactory learning circuitry without changing brain structure and confer to mosquitoes an ability to adapt to new hosts. -
Abstract Mosquitoes track odors, locate hosts, and find mates visually. The color of a food resource, such as a flower or warm-blooded host, can be dominated by long wavelengths of the visible light spectrum (green to red for humans) and is likely important for object recognition and localization. However, little is known about the hues that attract mosquitoes or how odor affects mosquito visual search behaviors. We use a real-time 3D tracking system and wind tunnel that allows careful control of the olfactory and visual environment to quantify the behavior of more than 1.3 million mosquito trajectories. We find that CO 2 induces a strong attraction to specific spectral bands, including those that humans perceive as cyan, orange, and red. Sensitivity to orange and red correlates with mosquitoes’ strong attraction to the color spectrum of human skin, which is dominated by these wavelengths. The attraction is eliminated by filtering the orange and red bands from the skin color spectrum and by introducing mutations targeting specific long-wavelength opsins or CO 2 detection. Collectively, our results show that odor is critical for mosquitoes’ wavelength preferences and that the mosquito visual system is a promising target for inhibiting their attraction to human hosts.more » « less
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Abstract Bed bugs ( Cimex lectularius ) have proliferated globally and have become one of the most challenging pests to control indoors. They are nocturnal and use multiple sensory cues to detect and orient towards their human hosts. After feeding, usually on a sleeping human, they return to a shelter on or around the sleeping surface, but not directly on the host. We hypothesized that although human skin odors attract hungry bed bugs, human skin compounds may also prevent arrestment on hosts. We used arrestment assays to test human skin swabs, extracts from human skin swabs, and pure compounds identified from human skin swabs. When given a choice, bed bugs preferred to arrest on substrates not previously conditioned by humans. These responses were consistent among laboratory-reared and apartment-collected bed bugs. The compounds responsible for this behavior were found to be extractable in hexane, and bed bugs responded to such extracts in a dose-dependent manner. Bioassay-guided fractionation paired with thin-layer chromatography, GC–MS, and LC–MS analyses suggested that triglycerides (TAGs), common compounds found on human skin, were preventing arrestment on shelters. Bed bugs universally avoided sheltering in TAG-treated shelters, which was independent of the number of carbons or the number of double bonds in the TAG. These results provide strong evidence that the complex of human skin compounds serve as multifunctional semiochemicals for bed bugs, with some odorants attracting host-seeking stages, and others (TAGs and possibly other compounds) preventing bed bug arrestment. Host chemistry, environmental conditions and the physiological state of bed bugs likely influence the dual nature behavioral responses of bed bugs to human skin compounds.more » « less
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Abstract Heterogeneities in infections among host populations may arise through differences in environmental conditions through two mechanisms. First, environmental conditions may alter host exposure to pathogens via effects on survival. Second, environmental conditions may alter host susceptibility, making infection more or less likely if contact between a host and pathogen occurs. Further, host susceptibility might be altered through acquired resistance, which hosts can develop, in some systems, through exposure to dead or decaying pathogens and their metabolites. Environmental conditions may alter the rates of pathogen decomposition, influencing the likelihood of hosts developing acquired resistance.
The present study primarily tests how environmental context influences the relative contributions of pathogen survival and per capita transmission on host infection prevalence using the amphibian chytrid fungus (
Batrachochytrium dendrobatidis ; Bd) as a model system. Secondarily, we evaluate how environmental context influences the decomposition of Bd because previous studies have shown that dead Bd and its metabolites can illicit acquired resistance in hosts. We conducted Bd survival and infection experiments and then fit models to discern how Bd mortality, decomposition and per capita transmission rates vary among water sources [e.g. artificial spring water (ASW) or water from three ponds].We found that infection prevalence differed among water sources, which was driven by differences in mortality rates of Bd, rather than differences in per capita transmission rates. Bd mortality rates varied among pond water treatments and were lower in ASW compared to pond water.
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Abstract Ecological succession of necrophilous insects follows a predictable sequence, related to their differential attraction to changing odor profiles associated with carrion and colonizing insects. However, the dependency of insect arrival on the duration of the carrion’s residency at a location has not been investigated. To assess the fidelity of necrophilous insects to carrion of specific decomposition ages, independent of its location, we monitored the decomposition of neonate pigs in one field and then simultaneously relocated carcasses of different decomposition ages to an ecologically similar but remote field. We examined the effects of decomposition age and relocation on the assembly of the necrophilous insect community, using a novel vented-chamber trap, which excluded all sensory cues except odors. Community composition differed over a 4-d decomposition period, showing that insects were differentially attracted to pigs of different decomposition ages. There was overall concordance between respective decomposition ages in the two fields, with similar relative abundances of taxa before and after transfer. Although different decomposition ages continued to attract different insects, differentiation of the necrophilous insect communities relative to the age of decomposition was less pronounced after transfer. The results of this study demonstrate that translocating a decomposing body to a new, but geographically and ecologically similar location continues the predicted insect succession, albeit with greater variance, based on olfactory cues alone. Several rare taxa were sampled only prior to relocation, including the first documentation of the invasive hairy maggot blow fly, Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae), in central North Carolina.
