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Parasites & Vectors Mar 2022In arboviral disease systems where the virus can be transmitted from male to female vectors and from one generation to the next, targeting the female (especially when...
BACKGROUND
In arboviral disease systems where the virus can be transmitted from male to female vectors and from one generation to the next, targeting the female (especially when she is gravid) can help alter the persistence of the virus in nature and its transmission. A typical example is Aedes aegypti, which has become unmanageable due to the development of insecticide resistance. Despite evidence that monomolecular surface films prevent the selection of genetic resistance, their potential in Aedes vector control remains largely unexplored.
METHODS
We examined the oviposition, egg retention, oocyte melanization, and female mortality of the Cayman Islands strain of Ae. aegypti, using choice (balanced and unbalanced) and no-choice bioassays involving Aquatain® Mosquito Formulation (AMF; Aquatain Products Pty Ltd.), a polydimethylsiloxane-based liquid used for mosquito control.
RESULTS
When presented with similar opportunities to oviposit in two sites treated with AMF and two other sites with untreated water (control), egg deposition rates were significantly higher in the untreated water sites than in the AMF-treated sites (P < 0.05). We also observed a matching pattern of egg deposition preference in environments with more options in terms of AMF-treated sites. Females laid significantly more eggs when water was the only available medium than when all sites were treated with AMF (P < 0.05). Also, significantly more mature eggs were withheld in the AMF no-choice environment than in the no-choice test involving only water (P < 0.05). Internal oocyte melanization was not observed in females from the oviposition arenas with the lowest AMF presence (equal-choice and water-based no-choice); in contrast, this physiological response intensified as the number of AMF-treated sites increased. Female death occurred at high rates in AMF-treated environments, and this response increased with the increasing presence of such egg deposition sites.
CONCLUSIONS
This study demonstrated that AMF acted as a deterrent signal to ovipositing Ae. aegypti and as an indirect adulticide. These results suggest that AMF may be a promising control tool against the dengue vector, and this warrants further evaluation under field settings.
Topics: Aedes; Animals; Female; Male; Mosquito Vectors; Oocytes; Oviposition; Silicon
PubMed: 35317811
DOI: 10.1186/s13071-022-05202-0 -
Chimia Nov 2022Insect eggs deposited on plants constitute a threat that has led to the evolution of sophisticated defenses. The interactions between insect eggs and plants are governed...
Insect eggs deposited on plants constitute a threat that has led to the evolution of sophisticated defenses. The interactions between insect eggs and plants are governed by a diverse variety of chemicals that inform butterflies about suitable hosts, repel gravid females, alert plants about the presence of an egg, act as signal molecules to induce defenses, directly impair egg development, and indirectly attract egg parasitoids. In recent years, significant progress has been made on the chemical identification, perception and role of compounds associated with oviposition. Knowledge on the genetic basis of oviposition-induced responses is also accumulating. An emerging theme is that insect eggs are not passive structures on leaves but induce complex responses that result from million years of coevolution.
Topics: Female; Animals; Butterflies; Insecta; Oviposition; Plant Leaves; Plants
PubMed: 38069786
DOI: 10.2533/chimia.2022.914 -
Annual Review of Entomology Jan 2023Insect eggs are exposed to a plethora of abiotic and biotic threats. Their survival depends on both an innate developmental program and genetically determined protective... (Review)
Review
Insect eggs are exposed to a plethora of abiotic and biotic threats. Their survival depends on both an innate developmental program and genetically determined protective traits provided by the parents. In addition, there is increasing evidence that () parents adjust the egg phenotype to the actual needs, () eggs themselves respond to environmental challenges, and () egg-associated microbes actively shape the egg phenotype. This review focuses on the phenotypic plasticity of insect eggs and their capability to adjust themselves to their environment. We outline the ways in which the interaction between egg and environment is two-way, with the environment shaping the egg phenotype but also with insect eggs affecting their environment. Specifically, insect eggs affect plant defenses, host biology (in the case of parasitoid eggs), and insect oviposition behavior. We aim to emphasize that the insect egg, although it is a sessile life stage, actively responds to and interacts with its environment.
Topics: Female; Animals; Insecta; Adaptation, Physiological; Oviposition; Plants; Phenotype; Ovum
PubMed: 36266253
DOI: 10.1146/annurev-ento-120120-100746 -
Biogerontology Feb 2023The early-life experience is important in modulating the late-life performance of individuals. It has been predicted that there were trade-offs between early-life...
The early-life experience is important in modulating the late-life performance of individuals. It has been predicted that there were trade-offs between early-life fitness and late-life success. Most of the studies on senescence have focused on the trade-offs between the reproduction and lifespan, and the influences of diet, mating, and other factors. Because the negative, non-consumptive effects of predators could also modulate the behaviour and underlying mechanisms of the prey, this study aimed to examine the different effects of predator-induced stress experienced in the early life compared with later life of the prey. The prey (Tyrophagus putrescentiae) was exposed to predation stress from the predator (Neoseiulus cucumeris) during different periods of its life (immature, oviposition period, and post-oviposition period). The results showed that the predation stress experienced during immature stages delayed development by 7.3% and prolonged lifespan by 9.7%, while predation stress experienced in the adult stage (both oviposition and post-oviposition periods) decreased lifespans of T. putrescentiae (by 24.8% and 28.7%, respectively). Predation stress experienced during immature stages also reduced female fecundity by 7.3%, whereas that experienced during the oviposition period reduced fecundity of the prey by 50.7%. This study demonstrated for the first time lifespan extension by exposure to predation stress when young and highlighted the importance of early-life experience to aging and lifespan.
Topics: Animals; Female; Longevity; Mites; Oviposition; Predatory Behavior
PubMed: 36085209
DOI: 10.1007/s10522-022-09990-x -
Current Biology : CB May 2023In a heterogeneous and changing environment, oviposition site selection strongly affects the survival and fitness of the offspring. Similarly, competition between larvae...
In a heterogeneous and changing environment, oviposition site selection strongly affects the survival and fitness of the offspring. Similarly, competition between larvae affects their prospects. However, little is known about the involvement of pheromones in regulating these processes. Here, we show that mated females of Drosophila melanogaster prefer to lay eggs on substrates containing extracts of conspecific larvae. After analyzing these extracts chemically, we test each compound in an oviposition assay and find that mated females display a dose-dependent preference to lay eggs on substrates spiked with (Z)-9-octadecenoic acid ethyl ester (OE). This egg-laying preference relies on gustatory receptor Gr32a and tarsal sensory neurons expressing this receptor. The concentration of OE also regulates larval place choice in a dose-dependent manner. Physiologically, OE activates female tarsal Gr32a neurons. In conclusion, our results reveal a cross-generation communication strategy essential for oviposition site selection and regulation of larval density.
Topics: Animals; Female; Drosophila; Drosophila melanogaster; Oviposition; Pheromones; Drosophila Proteins; Larva
PubMed: 37098339
DOI: 10.1016/j.cub.2023.03.090 -
Parasites & Vectors Aug 2023Olfaction plays an important role in the selection and assessment of oviposition sites by mosquitoes. Volatile organic compounds (VOCs) associated with potential...
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.
Topics: Animals; Female; Aedes; Odorants; Oviposition; Smell; Larva; Water; Volatile Organic Compounds
PubMed: 37542293
DOI: 10.1186/s13071-023-05867-1 -
Journal of Genetics Dec 2008Extensive research has been carried out to understand how circadian clocks regulate various physiological processes in organisms. The discovery of clock genes and the... (Review)
Review
Extensive research has been carried out to understand how circadian clocks regulate various physiological processes in organisms. The discovery of clock genes and the molecular clockwork has helped researchers to understand the possible role of these genes in regulating various metabolic processes. In Drosophila melanogaster, many studies have shown that the basic architecture of circadian clocks is multi-oscillatory. In nature, different neuronal subgroups in the brain of D. melanogaster have been demonstrated to control different circadian behavioural rhythms or different aspects of the same circadian rhythm. Among the circadian phenomena that have been studied so far in Drosophila, the egg-laying rhythm is unique, and relatively less explored. Unlike most other circadian rhythms, the egg-laying rhythm is rhythmic under constant light conditions, and the endogenous or free-running period of the rhythm is greater than those of most other rhythms. Although the clock genes and neurons required for the persistence of adult emergence and activity/rest rhythms have been studied extensively, those underlying the circadian egg-laying rhythm still remain largely unknown. In this review, we discuss our current understanding of the circadian egg-laying rhythm in D. melanogaster, and the possible molecular and physiological mechanisms that control the rhythmic output of the egg-laying process.
Topics: Animals; Circadian Rhythm; Drosophila Proteins; Drosophila melanogaster; Insect Hormones; Models, Biological; Oviposition; Sexual Behavior, Animal; Zygote
PubMed: 19147938
DOI: 10.1007/s12041-008-0072-9 -
Parasites & Vectors Jun 2020Gravid females assess the conditions of oviposition sites to secure the growth and survival of their offspring. Conspecific-occupied sites may signal suitable...
BACKGROUND
Gravid females assess the conditions of oviposition sites to secure the growth and survival of their offspring. Conspecific-occupied sites may signal suitable oviposition sites but may also impose risk due to competition or cannibalism at high population density or heterogeneous larval stage structure, respectively. Chemicals in the habitat, including chemicals emitted from other organisms, serve as cues for females to assess habitat conditions. Here, we investigated the attraction and oviposition preference of the Old World cutaneous leishmaniasis vector, Phlebotomus papatasi, to young and old conspecific stages, including eggs and evaluated the effect of a semiochemical associated with eggs and neonate larvae.
METHODS
Attraction and oviposition preference of Ph. papatasi to each of various life stages (eggs, first-, second-, third-, fourth-instar larvae, pupae and male and female adults) was investigated using cage and oviposition jar behavioral assays. Identification of organic chemical compounds extracted from eggs was performed using GC-MS and chemicals were tested in the same behavioral assays in a dose-response manner. Behavioral responses were statistically analyzed using logistic models.
RESULTS
Gravid Ph. papatasi females were significantly attracted to and preferred to oviposit on medium containing young life stages (eggs and first instars). This preference decreased towards older life stages. Dose effect of eggs indicated a hump-shaped response with respect to attraction but a concave-up pattern with respect to oviposition. Chemical analysis of semiochemicals from eggs and first-instar larvae revealed the presence of dodecanoic acid (DA) and isovaleric acid. Sand flies were attracted to and laid more eggs at the lowest DA dose tested followed by a negative dose-response.
CONCLUSIONS
Findings corroborated our hypothesis that gravid sand flies should prefer early colonized oviposition sites as indicators of site suitability but avoid sites containing older stages as indicators of potential competition. Findings also supported the predictions of our hump-shaped oviposition regulation (HSR) model, with attraction to conspecific eggs at low-medium densities and switching to repellence at high egg densities. This oviposition behavior is mediated by DA that was identified from surface extracts of both eggs and first-instar larvae. Isovaleric acid was also found in extracts of both stages.
Topics: Animals; Behavior, Animal; Female; Hemiterpenes; Larva; Lauric Acids; Male; Oviposition; Ovum; Pentanoic Acids; Pheromones; Phlebotomus; Pupa
PubMed: 32493498
DOI: 10.1186/s13071-020-04151-w -
Medical and Veterinary Entomology Dec 2023Vector control is still the recommended approach to avoid arbovirus outbreaks. Herein, we investigate oviposition preferences of Aedes aegypti (Diptera: Culicidae)...
Vector control is still the recommended approach to avoid arbovirus outbreaks. Herein, we investigate oviposition preferences of Aedes aegypti (Diptera: Culicidae) females under a semi-field structure Rio de Janeiro, Brazil. For that, in Experiment 1, we used two settings: 'Single items', which included as containers drain, beer bottle, bucket, car tyre, water tank, and a potted Peace Lily (Spathiphyllum wallisii) in a saucer with water, or 'Multiple containers', as an urban simulation, in which one drain, two additional beer bottles, and an extra plant pot saucer were added. Experiment 2 (sensory cues) used five variations of potted plant, each one varying in the range of sensory cues known to attract gravid females to oviposition containers. Our results indicate that gravid Ae. aegypti prefer to oviposit close to the ground and in open water containers with organic compounds from plant watering. Domestic large artificial containers containing tap water received significantly fewer eggs, except for the car tyre, which exhibited as many eggs as the potted plant. We also show that visual (potted plant shape) and olfactory clues (odour of the plant or from water containing organic matter) were equally attractive separately as were these stimuli together.
Topics: Female; Animals; Aedes; Oviposition; Mosquito Vectors; Brazil; Water
PubMed: 37265439
DOI: 10.1111/mve.12670 -
Insect Science Feb 2023Diaphorina citri is an important vector of Citrus Huanglongbing (HLB) disease. After feeding on young host plant shoots, the population of D. citri can increase...
Diaphorina citri is an important vector of Citrus Huanglongbing (HLB) disease. After feeding on young host plant shoots, the population of D. citri can increase significantly. Females also only lay eggs on young shoots. However, there are few studies on the mechanism of this phenomenon. Exogenous nutrient signals can affect the insulin signaling system of D. citri after feeding on young shoots. In this study, the expression of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system of D. citri was upregulated after feeding on young shoots. After being silenced by RNA interference technology, the results showed that the number of oviposited eggs of D. citri was significantly decreased and the ovarian development was inhibited with severe vacuolation. In addition, detection using quantitative reverse transcription-polymerase chain reaction showed that the upstream regulatory gene DcRheb of the target of rapamycin (TOR) pathway and the downstream reproduction-related DcVg gene were also significantly downregulated. These results suggest that feeding upon young shoots may upregulate the expression levels of upstream factors DcILP1, DcILP2, and DcIR in the insulin signaling system. The signal will be through upregulating the expression of DcRheb, an upstream gene of the TOR signaling pathway. This in turn influences yolk metabolism, which eventually causes the ovaries of female D. citri to mature and therefore initiate oviposition behavior.
Topics: Female; Animals; Insulin; Oviposition; Citrus; Peptides; RNA Interference; Hemiptera; Plant Diseases
PubMed: 35510515
DOI: 10.1111/1744-7917.13048