ABSTRACT The olfactory sense detects a plethora of behaviorally relevant odor molecules; gene fam... more ABSTRACT The olfactory sense detects a plethora of behaviorally relevant odor molecules; gene families involved in olfaction exhibit high diversity in different animal phyla. Insects detect volatile molecules using olfactory (OR) or ionotropic receptors (IR) and in some cases gustatory receptors (GRs). While IRs are expressed in olfactory organs across Protostomia, ORs have been hypothesized to be an adaptation to a terrestrial insect lifestyle. We investigated the olfactory system of the primary wingless bristletail Lepismachilis y-signata (Archaeognatha), the firebrat Thermobia domestica (Zygentoma) and the neopteran leaf insect Phyllium siccifolium (Phasmatodea). ORs and the olfactory coreceptor (Orco) are with very high probability lacking in Lepismachilis; in Thermobia we have identified three Orco candidates, and in Phyllium a fully developed OR/Orco-based system. We suggest that ORs did not arise as an adaptation to a terrestrial lifestyle, but evolved later in insect evolution, with Orco being present before the appearance of ORs. DOI: http://dx.doi.org/10.7554/eLife.02115.001.
Tsetse flies transmit trypanosomes—parasites that cause devastating diseases in humans and livest... more Tsetse flies transmit trypanosomes—parasites that cause devastating diseases in humans and livestock—across much of sub-Saharan Africa. Chemical communication through volatile pheromones is common among insects; however, it remains unknown if and how such chemical communication occurs in tsetse flies. We identified methyl palmitoleate (MPO), methyl oleate, and methyl palmitate as compounds that are produced by the tsetse fly Glossina morsitans and elicit strong behavioral responses. MPO evoked a behavioral response in male—but not virgin female— G. morsitans . G. morsitans males mounted females of another species, Glossina fuscipes , when they were treated with MPO. We further identified a subpopulation of olfactory neurons in G. morsitans that increase their firing rate in response to MPO and showed that infecting flies with African trypanosomes alters the flies’ chemical profile and mating behavior. The identification of volatile attractants in tsetse flies may be useful for reducing disease spread.
Adaptations to anthropogenic domestic habitats contribute to the success of the mosquito Aedes ae... more Adaptations to anthropogenic domestic habitats contribute to the success of the mosquito Aedes aegypti as a major global vector of several arboviral diseases. The species inhabited African forests before expanding into domestic habitats and spreading to other continents. Despite a well‐studied evolutionary history, how this species initially moved into human settlements in Africa remains unclear. During this initial habitat transition, African Ae. aegypti switched their larval sites from natural water containers like tree holes to artificial containers like clay pots. Little is known about how these natural versus artificial containers differ in their characteristics. Filling this knowledge gap could provide valuable information for studying the evolution of Ae. aegypti associated with larval habitat changes. As an initial effort, in this study, we characterized the microenvironments of Ae. aegypti larval sites in forest and domestic habitats in two African localities: La Lopé, Gabon, and Rabai, Kenya. Specifically, we measured the physical characteristics, microbial density, bacterial composition, and volatile chemical profiles of multiple larval sites. In both localities, comparisons between natural containers in the forests and artificial containers in the villages revealed significantly different microenvironments. We next examined whether the between‐habitat differences in larval site microenvironments lead to differences in oviposition, a key behavior affecting larval distribution. Forest Ae. aegypti readily accepted the artificial containers we placed in the forests. Laboratory choice experiments also did not find distinct oviposition preferences between forest and village Ae. aegypti colonies. These results suggested that African Ae. aegypti are likely generalists in their larval site choices. This flexibility to accept various containers with a wide range of physical, microbial, and chemical conditions might allow Ae. aegypti to use human‐stored water as fallback larval sites during dry seasons, which is hypothesized to have initiated the domestic evolution of Ae. aegypti.
Similar spatial odor representation patterns between PNs and OSNs in the AL. (a) Spatial response... more Similar spatial odor representation patterns between PNs and OSNs in the AL. (a) Spatial response patterns for each odor are reconstructed on a template AL using odor response intensity of the 31 PN classes. (b) Spatial response patterns for each odor are reconstructed on a template AL using odor response intensity of the 29 OSN classes. In each map, the AL is viewed from anterior (top) and posterior (bottom). Each glomerulus name is indicated on the template AL (bottom right). Scale bars = 20 μm. (PDF 105472 kb)
Odor response intensity of all individual PNs. Odor response intensity of each PN to 17 odors for... more Odor response intensity of all individual PNs. Odor response intensity of each PN to 17 odors for each glomerulus, calculated by using spike frequencies during a 1-s odor stimulation period. n indicates the number of PNs recorded for each glomerulus. Odor responses of different PNs within the same PN class are indicated by different colors. The order of the 17 odors is arranged as in the inset on the bottom right for all graphs. (PDF 822 kb)
The agricultural pest Drosophila suzukii differs from most other Drosophila species in that it la... more The agricultural pest Drosophila suzukii differs from most other Drosophila species in that it lays eggs in ripe, rather than overripe, fruit. Previously we showed that changes in bitter taste sensation accompanied this adaptation (Dweck et al., 2021). Here we show that D. suzukii has also undergone a variety of changes in sweet taste sensation. D. suzukii has a weaker preference than D. melanogaster for laying eggs on substrates containing all three primary fruit sugars: sucrose, fructose, and glucose. Major subsets of D. suzukii taste sensilla have lost electrophysiological responses to sugars. Expression of several key sugar receptor genes is reduced in the taste organs of D. suzukii. By contrast, certain mechanosensory channel genes, including nompC, are expressed at higher levels in the taste organs of D. suzukii, which has a higher preference for stiff substrates. Finally, we find that D. suzukii responds differently from D. melanogaster to combinations of sweet and mechanosen...
Adaptations to anthropogenic domestic habitats contribute to the success of mosquito Aedes aegypt... more Adaptations to anthropogenic domestic habitats contribute to the success of mosquito Aedes aegypti as a major global vector of several arboviral diseases. The species inhabited African forests before expanding into domestic habitats and spreading to the rest of the world. Despite a well-studied evolutionary history, how this species initially moved into human settlements in Africa remains unclear. During this initial habitat transition, Ae. aegypti switched from using natural containers like tree holes as larval breeding sites to using artificial containers like clay pots. Little is known about how these natural versus artificial containers differ in their environments, or whether Ae. aegypti in forest versus domestic habitats evolved any corresponding incipient behavioral divergence, such as in oviposition. To address these gaps, we first characterized physical characteristics, larval density, microbial density, bacterial composition, and volatile profiles of natural versus artific...
ABSTRACT The olfactory sense detects a plethora of behaviorally relevant odor molecules; gene fam... more ABSTRACT The olfactory sense detects a plethora of behaviorally relevant odor molecules; gene families involved in olfaction exhibit high diversity in different animal phyla. Insects detect volatile molecules using olfactory (OR) or ionotropic receptors (IR) and in some cases gustatory receptors (GRs). While IRs are expressed in olfactory organs across Protostomia, ORs have been hypothesized to be an adaptation to a terrestrial insect lifestyle. We investigated the olfactory system of the primary wingless bristletail Lepismachilis y-signata (Archaeognatha), the firebrat Thermobia domestica (Zygentoma) and the neopteran leaf insect Phyllium siccifolium (Phasmatodea). ORs and the olfactory coreceptor (Orco) are with very high probability lacking in Lepismachilis; in Thermobia we have identified three Orco candidates, and in Phyllium a fully developed OR/Orco-based system. We suggest that ORs did not arise as an adaptation to a terrestrial lifestyle, but evolved later in insect evolution, with Orco being present before the appearance of ORs. DOI: http://dx.doi.org/10.7554/eLife.02115.001.
Tsetse flies transmit trypanosomes—parasites that cause devastating diseases in humans and livest... more Tsetse flies transmit trypanosomes—parasites that cause devastating diseases in humans and livestock—across much of sub-Saharan Africa. Chemical communication through volatile pheromones is common among insects; however, it remains unknown if and how such chemical communication occurs in tsetse flies. We identified methyl palmitoleate (MPO), methyl oleate, and methyl palmitate as compounds that are produced by the tsetse fly Glossina morsitans and elicit strong behavioral responses. MPO evoked a behavioral response in male—but not virgin female— G. morsitans . G. morsitans males mounted females of another species, Glossina fuscipes , when they were treated with MPO. We further identified a subpopulation of olfactory neurons in G. morsitans that increase their firing rate in response to MPO and showed that infecting flies with African trypanosomes alters the flies’ chemical profile and mating behavior. The identification of volatile attractants in tsetse flies may be useful for reducing disease spread.
Adaptations to anthropogenic domestic habitats contribute to the success of the mosquito Aedes ae... more Adaptations to anthropogenic domestic habitats contribute to the success of the mosquito Aedes aegypti as a major global vector of several arboviral diseases. The species inhabited African forests before expanding into domestic habitats and spreading to other continents. Despite a well‐studied evolutionary history, how this species initially moved into human settlements in Africa remains unclear. During this initial habitat transition, African Ae. aegypti switched their larval sites from natural water containers like tree holes to artificial containers like clay pots. Little is known about how these natural versus artificial containers differ in their characteristics. Filling this knowledge gap could provide valuable information for studying the evolution of Ae. aegypti associated with larval habitat changes. As an initial effort, in this study, we characterized the microenvironments of Ae. aegypti larval sites in forest and domestic habitats in two African localities: La Lopé, Gabon, and Rabai, Kenya. Specifically, we measured the physical characteristics, microbial density, bacterial composition, and volatile chemical profiles of multiple larval sites. In both localities, comparisons between natural containers in the forests and artificial containers in the villages revealed significantly different microenvironments. We next examined whether the between‐habitat differences in larval site microenvironments lead to differences in oviposition, a key behavior affecting larval distribution. Forest Ae. aegypti readily accepted the artificial containers we placed in the forests. Laboratory choice experiments also did not find distinct oviposition preferences between forest and village Ae. aegypti colonies. These results suggested that African Ae. aegypti are likely generalists in their larval site choices. This flexibility to accept various containers with a wide range of physical, microbial, and chemical conditions might allow Ae. aegypti to use human‐stored water as fallback larval sites during dry seasons, which is hypothesized to have initiated the domestic evolution of Ae. aegypti.
Similar spatial odor representation patterns between PNs and OSNs in the AL. (a) Spatial response... more Similar spatial odor representation patterns between PNs and OSNs in the AL. (a) Spatial response patterns for each odor are reconstructed on a template AL using odor response intensity of the 31 PN classes. (b) Spatial response patterns for each odor are reconstructed on a template AL using odor response intensity of the 29 OSN classes. In each map, the AL is viewed from anterior (top) and posterior (bottom). Each glomerulus name is indicated on the template AL (bottom right). Scale bars = 20 μm. (PDF 105472 kb)
Odor response intensity of all individual PNs. Odor response intensity of each PN to 17 odors for... more Odor response intensity of all individual PNs. Odor response intensity of each PN to 17 odors for each glomerulus, calculated by using spike frequencies during a 1-s odor stimulation period. n indicates the number of PNs recorded for each glomerulus. Odor responses of different PNs within the same PN class are indicated by different colors. The order of the 17 odors is arranged as in the inset on the bottom right for all graphs. (PDF 822 kb)
The agricultural pest Drosophila suzukii differs from most other Drosophila species in that it la... more The agricultural pest Drosophila suzukii differs from most other Drosophila species in that it lays eggs in ripe, rather than overripe, fruit. Previously we showed that changes in bitter taste sensation accompanied this adaptation (Dweck et al., 2021). Here we show that D. suzukii has also undergone a variety of changes in sweet taste sensation. D. suzukii has a weaker preference than D. melanogaster for laying eggs on substrates containing all three primary fruit sugars: sucrose, fructose, and glucose. Major subsets of D. suzukii taste sensilla have lost electrophysiological responses to sugars. Expression of several key sugar receptor genes is reduced in the taste organs of D. suzukii. By contrast, certain mechanosensory channel genes, including nompC, are expressed at higher levels in the taste organs of D. suzukii, which has a higher preference for stiff substrates. Finally, we find that D. suzukii responds differently from D. melanogaster to combinations of sweet and mechanosen...
Adaptations to anthropogenic domestic habitats contribute to the success of mosquito Aedes aegypt... more Adaptations to anthropogenic domestic habitats contribute to the success of mosquito Aedes aegypti as a major global vector of several arboviral diseases. The species inhabited African forests before expanding into domestic habitats and spreading to the rest of the world. Despite a well-studied evolutionary history, how this species initially moved into human settlements in Africa remains unclear. During this initial habitat transition, Ae. aegypti switched from using natural containers like tree holes as larval breeding sites to using artificial containers like clay pots. Little is known about how these natural versus artificial containers differ in their environments, or whether Ae. aegypti in forest versus domestic habitats evolved any corresponding incipient behavioral divergence, such as in oviposition. To address these gaps, we first characterized physical characteristics, larval density, microbial density, bacterial composition, and volatile profiles of natural versus artific...
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