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Khan Z, Bohman B, Ignell R, Hill SR. Odour-mediated oviposition site selection in Aedes aegypti depends on aquatic stage and density. Parasit Vectors 2023; 16:264. [PMID: 37542293 PMCID: PMC10403918 DOI: 10.1186/s13071-023-05867-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/04/2023] [Indexed: 08/06/2023] Open
Abstract
BACKGROUND Olfaction plays an important role in the selection and assessment of oviposition sites by mosquitoes. Volatile organic compounds (VOCs) associated with potential breeding sites affect the behaviour of gravid mosquitoes, with VOCs from aquatic stages of conspecific mosquitoes influencing and regulating oviposition. The purpose of this study was to conduct a systematic analysis of the behavioural response of gravid Aedes aegypti to conspecific aquatic stage-conditioned water, to identify the associated bioactive VOCs and to determine how blends of these VOCs regulate oviposition site selection and stimulate egg-laying. METHODS Using a multi-choice olfactory oviposition assay, controlling for other sensory modalities, the responses of individual females to water conditioned with different densities of conspecific aquatic stages were assessed. The conditioned water samples from the most preferred density of each aquatic stage were subsequently compared to each other using the same oviposition assay and analysed using an analysis of variance (ANOVA) followed by a Tukey post-hoc test. Using combined gas chromatography and electroantennographic detection or mass spectrometry, bioactive VOCs from the preferred density of each aquatic stage were identified. Synthetic blends were prepared based on the identified ratios of bioactive VOCs in the aquatic stages, and then tested to determine the oviposition choice of Ae. aegypti in a dose-dependent manner, against a solvent control, using a dual-choice assay. This dataset was analysed using nominal logistic regression followed by an odds ratio comparison. RESULTS Gravid Ae. aegypti responded stage- and density-dependently to water conditioned with eggs, second- and fourth-instar larvae, and pupal exuviae, but not to water conditioned with pupae alone. Multi-choice assays demonstrated that gravid mosquitoes preferred to oviposit in water conditioned with fourth-instar larvae, over the other aquatic stage-conditioned water. Gravid Ae. aegypti were attracted, and generally stimulated, to oviposit in a dose-dependent manner to the individual identified synthetic odour blends for the different aquatic stages. CONCLUSIONS Intraspecific VOCs regulate oviposition site selection in Ae. aegypti in a stage- and density-dependent manner. We discuss the need for further studies to evaluate the identified synthetic blends to modulate the odour-mediated oviposition of Ae. aegypti under field conditions.
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Affiliation(s)
- Zaid Khan
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 190, 234 22, Lomma, Sweden
| | - Björn Bohman
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 190, 234 22, Lomma, Sweden
| | - Rickard Ignell
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 190, 234 22, Lomma, Sweden
| | - Sharon Rose Hill
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 190, 234 22, Lomma, Sweden.
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Mosquera KD, Martínez Villegas LE, Rocha Fernandes G, Rocha David M, Maciel-de-Freitas R, A Moreira L, Lorenzo MG. Egg-laying by female Aedes aegypti shapes the bacterial communities of breeding sites. BMC Biol 2023; 21:97. [PMID: 37101136 PMCID: PMC10134544 DOI: 10.1186/s12915-023-01605-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 04/18/2023] [Indexed: 04/28/2023] Open
Abstract
BACKGROUND Aedes aegypti, the main arboviral mosquito vector, is attracted to human dwellings and makes use of human-generated breeding sites. Past research has shown that bacterial communities associated with such sites undergo compositional shifts as larvae develop and that exposure to different bacteria during larval stages can have an impact on mosquito development and life-history traits. Based on these facts, we hypothesized that female Ae. aegypti shape the bacteria communities of breeding sites during oviposition as a form of niche construction to favor offspring fitness. RESULTS To test this hypothesis, we first verified that gravid females can act as mechanical vectors of bacteria. We then elaborated an experimental scheme to test the impact of oviposition on breeding site microbiota. Five different groups of experimental breeding sites were set up with a sterile aqueous solution of larval food, and subsequently exposed to (1) the environment alone, (2) surface-sterilized eggs, (3) unsterilized eggs, (4) a non-egg laying female, or (5) oviposition by a gravid female. The microbiota of these differently treated sites was assessed by amplicon-oriented DNA sequencing once the larvae from the sites with eggs had completed development and formed pupae. Microbial ecology analyses revealed significant differences between the five treatments in terms of diversity. In particular, between-treatment shifts in abundance profiles were detected, showing that females induce a significant decrease in microbial alpha diversity through oviposition. In addition, indicator species analysis pinpointed bacterial taxa with significant predicting values and fidelity coefficients for the samples in which single females laid eggs. Furthermore, we provide evidence regarding how one of these indicator taxa, Elizabethkingia, exerts a positive effect on the development and fitness of mosquito larvae. CONCLUSIONS Ovipositing females impact the composition of the microbial community associated with a breeding site, promoting certain bacterial taxa over those prevailing in the environment. Among these bacteria, we found known mosquito symbionts and showed that they can improve offspring fitness if present in the water where eggs are laid. We deem this oviposition-mediated bacterial community shaping as a form of niche construction initiated by the gravid female.
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Affiliation(s)
- Katherine D Mosquera
- Vector Behavior and Pathogen Interaction Group, René Rachou Institute-FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil
| | - Luis Eduardo Martínez Villegas
- Department of Entomology, The Ohio State University, 2001 Fyffe Rd., Room 232 Howlett Hall, Columbus, OH, 43210, USA
- Mosquito Vectors: Endosymbionts and Pathogen-Vector Interactions Group, René Rachou Institute-FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil
| | | | - Mariana Rocha David
- Laboratory of Hematozoa Transmitting Mosquitoes, Oswaldo Cruz Institute-FIOCRUZ, Rio de Janeiro, Brazil
| | - Rafael Maciel-de-Freitas
- Laboratory of Hematozoa Transmitting Mosquitoes, Oswaldo Cruz Institute-FIOCRUZ, Rio de Janeiro, Brazil
| | - Luciano A Moreira
- Mosquito Vectors: Endosymbionts and Pathogen-Vector Interactions Group, René Rachou Institute-FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil
| | - Marcelo G Lorenzo
- Vector Behavior and Pathogen Interaction Group, René Rachou Institute-FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil.
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Mosquera KD, Khan Z, Wondwosen B, Alsanius B, Hill SR, Ignell R, Lorenzo MG. Odor-mediated response of gravid Aedes aegypti to mosquito-associated symbiotic bacteria. Acta Trop 2022; 237:106730. [PMID: 36280207 DOI: 10.1016/j.actatropica.2022.106730] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/18/2022] [Accepted: 10/20/2022] [Indexed: 11/16/2022]
Abstract
Complex oviposition decisions allow gravid Aedes aegypti mosquitoes to select suitable sites for egg-laying to increase the probability that their progeny will thrive. The bacterial communities present in larval niches influence mosquito oviposition behavior, and gravid mosquitoes transmit key microbial associates to breeding sites during oviposition. Our study evaluated whether symbiotic Klebsiella sp., which are strongly associated with mosquitoes, emit volatiles that affect mosquito oviposition decisions. Dual-choice behavioral assays demonstrated that volatile organic compounds emitted by Klebsiella sp. induce a preference in oviposition decisions by Ae. aegypti. Bacterial headspace volatiles were sampled by solid-phase microextraction, and subsequent combined gas chromatography and electroantennogram detection analysis, revealed that the antennae of gravid females detect two compounds present in the Klebsiella sp. headspace. These compounds were identified by gas chromatography and mass spectrometry as 2-ethyl hexanol and 2,4-di‑tert-butylphenol. The binary blend of these compounds elicited a dose-dependent egg-laying preference by gravid mosquitoes. We propose that bacterial symbionts, which are associated with gravid mosquitoes and may be transferred to aquatic habitats during egg-laying, together with their volatiles act as oviposition cues indicating the suitability of active breeding sites to conspecific females.
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Affiliation(s)
- Katherine D Mosquera
- Vector Behavior and Pathogen Interaction Group, Instituto René Rachou, Fiocruz Minas, Belo Horizonte, Brazil
| | - Zaid Khan
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Betelehem Wondwosen
- Department of Zoological Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Beatrix Alsanius
- Microbial Horticulture Group, Department of Biosystems and Technology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Sharon R Hill
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Rickard Ignell
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Marcelo G Lorenzo
- Vector Behavior and Pathogen Interaction Group, Instituto René Rachou, Fiocruz Minas, Belo Horizonte, Brazil.
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Kinga H, Kengne-Ouafo JA, King SA, Egyirifa RK, Aboagye-Antwi F, Akorli J. Water Physicochemical Parameters and Microbial Composition Distinguish Anopheles and Culex Mosquito Breeding Sites: Potential as Ecological Markers for Larval Source Surveillance. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1817-1826. [PMID: 35920087 DOI: 10.1093/jme/tjac115] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Indexed: 05/19/2023]
Abstract
The presence of mosquitoes in an area is dependent on the availability of suitable breeding sites that are influenced by several environmental factors. Identification of breeding habitats for vector surveillance and larval source management is key to disease control programs. We investigated water quality parameters and microbial composition in selected mosquito breeding sites in urban Accra, Ghana and associated these with abundance of Anopheles (Diptera: Culicidae) and Culex (Diptera: Culicidae) larvae. Physicochemical parameters and microbial composition explained up to 72% variance among the breeding sites and separated Anopheles and Culex habitats (P < 0.05). Anopheles and Culex abundances were commonly influenced by water temperature, pH, nitrate, and total hardness with contrasting impacts on the two mosquito species. In addition, total dissolved solids, biochemical oxygen demand, and alkalinity uniquely influenced Anopheles abundance, while total suspended solids, phosphate, sulphate, ammonium, and salinity were significant determinants for Culex. The correlation of these multiple parameters with the occurrence of each mosquito species was high (R2 = 0.99, P < 0.0001). Bacterial content assessment of the breeding ponds revealed that the most abundant bacterial phyla were Patescibacteria, Cyanobacteria, and Proteobacteria, constituting >70% of the total bacterial richness. The oligotrophic Patescibacteria was strongly associated with Anopheles suggestive of the mosquito's adaptation to environments with less nutrients, while predominance of Cyanobacteria, indicative of rich nutritional source was associated with Culex larval ponds. We propose further evaluation of these significant abiotic and biotic parameters in field identification of larval sources and how knowledge of these can be harnessed effectively to reduce conducive breeding sites for mosquitoes.
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Affiliation(s)
- Harriet Kinga
- African Regional Postgraduate Program in Insect Science, University of Ghana, Legon, Ghana
| | - Jonas A Kengne-Ouafo
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Medical Entomology Department, Centre of Research in Infectious Diseases (CRID), Yaounde, Cameroon
| | - Sandra A King
- Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Richardson K Egyirifa
- Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
| | - Fred Aboagye-Antwi
- African Regional Postgraduate Program in Insect Science, University of Ghana, Legon, Ghana
- Department of Animal Biology and Conservation Sciences, University of Ghana, Legon, Ghana
| | - Jewelna Akorli
- West African Centre for Cell Biology of Infectious Pathogens, University of Ghana, Legon, Ghana
- Department of Parasitology, Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana
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Differential Hatching, Development, Oviposition, and Longevity Patterns among Colombian Aedes aegypti Populations. INSECTS 2022; 13:insects13060536. [PMID: 35735873 PMCID: PMC9224916 DOI: 10.3390/insects13060536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/06/2022] [Accepted: 06/08/2022] [Indexed: 02/01/2023]
Abstract
Simple Summary Aedes aegypti is a mosquito that transmits viruses responsible for several diseases in humans, such as dengue, Zika, and chikungunya. It is crucial to study mosquito populations from different countries and regions because control of disease transmission with insecticides can be more effective if adjusted to each population’s characteristics. For this reason, we determined several features of mosquitoes captured in different cities of Colombia: Neiva, Bello, Itagüí, and Riohacha. These included the length of their lifespan, the number of eggs they lay, and the stages in which they die. We found specific patterns for each population. This knowledge will help control programs determine the optimal times to apply insecticides and make surveillance, as well as the type of insecticide used. Abstract Dengue, Zika, and chikungunya are arboviral diseases for which there are no effective therapies or vaccines. The only way to avoid their transmission is by controlling the vector Aedes aegypti, but insecticide resistance limits this strategy. To generate relevant information for surveillance and control mechanisms, we determined life cycle parameters, including longevity, fecundity, and mortality, of Colombian Ae. aegypti populations from four different geographical regions: Neiva, Bello, Itagüí, and Riohacha. When reared at 28 °C, Bello had the shortest development time, and Riohacha had the longest. Each mosquito population had its own characteristic fecundity pattern during four gonotrophic cycles. The survival curves of each population were significantly different, with Riohacha having the longest survival in both males and females and Bello the shortest. High mortality was observed in mosquitoes from Neiva in the egg stage and for Bello in the pupae stage. Finally, when mosquitoes from Neiva and Bello were reared at 35 °C, development times and mortality were severely affected. In conclusion, each population has a unique development pattern with an innate trace in their biological characteristics that confers vulnerability in specific stages of development.
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