Skip Oviposition Research Articles

Modeling the effects of climate change on the population dynamics of mosquitoes that are vectors of infectious diseases

We incorporate almost periodic functions in a mosquito model to take into account a loss of synchronicity in the population dynamics of mosquitoes due to climate change. The model takes into account the skip oviposition strategy that is associated with the mosquitoes that are vectors of infectious diseases as dengue, malaria and leishmaniasis. We prove existence and uniqueness of a stable almost periodic solution for some conditions over the parameters of the model. Numerical simulations are performed using values estimated for the life cycle of Aedes albopictus gathered in literature. The results show that the vector population can be underestimated or overestimated if an almost periodic dynamics is approximated by a periodic dynamics. Therefore, using an almost seasonal model can be more adequate to design breeding habitat-targeted mosquito control strategies when seasonal drivers are modeled since climate-mediated shifts can induce a loss of periodicity in environmental drivers.

Artificial light at night has species‐specific effects on oviposition behavior of mosquitoes

AbstractArtificial light at night (ALAN) is a pervasive and growing issue worldwide. ALAN disrupts the physiology and natural crepuscular and nocturnal behavior of organisms, with widely observed effects on insects. Mosquitoes (Diptera: Culicidae) are disease vectors that evaluate and select freshwater habitats as oviposition sites. This behavior has both ecological and epidemiological implications. However, it is unknown how ALAN affects mosquito oviposition. We compared oviposition rates in outdoor mesocosms exposed to light‐emitting diodes (LED, 3000 K, ca. 13 lux) with dark controls. We assayed the oviposition behavior of natural populations of mosquitoes by quantifying mosquito eggs (Culex restuans Theobald and Ochlerotatus japonicus Theobald) deposited in the experimental mesocosms over 7 days. Mosquitoes had species‐specific responses to ALAN. Mean cumulative Cx. restuans egg raft deposition was greater in control pools than in ALAN pools (21 vs. 10 eggs). We observed no response of Oc. japonicus, potentially reflecting the risk associated with the alternative oviposition strategies of the two species (eggs rafts vs. skip oviposition). Our results show that ALAN has species‐specific effects on organisms, thereby complicating our understanding of the behavioral and potential ecological and epidemiological effects of this novel anthropogenic stressor.

Spatial Bet Hedging in Sand Fly Oviposition: Factors Affecting Skip Oviposition in Phlebotomus papatasi Sand Flies.

Skip oviposition is considered as an example of spatial bet hedging and involves a tradeoff between the benefit of reducing the risk of complete reproductive failure due to stochastic loss of a breeding site and the energetic and mortality costs associated with dispersal across several oviposition sites. Skip oviposition has been studied extensively for container-breeding mosquitoes but has never been studied with sand flies. By conducting a series of bioassays using solitary gravid females exposed to varying numbers of oviposition sites and to oviposition sites of variable quality at small (oviposition jar) and medium (free-flight cage) scales, we showed that sand flies exhibited skip oviposit at both scales. Specifically, with low-quality oviposition sites, females spread their eggs across several oviposition sites with total egg clutch size remaining constant and number of eggs per oviposition site decreasing with increasing number of oviposition sites. With variable quality sites, sand flies biased their oviposition to sites containing increasing levels of organic matter (OM), but also laid eggs in poor-quality sites; a behavior consistent with spatial bet hedging. We also demonstrated that the presence of OM stimulated larger egg clutch size and increased percent skip oviposition. Skip oviposition was less frequent at the free flight cage scale. But, at this scale, females were shown to be stimulated to lay more eggs when in the presence of other females than when alone.

Using sibship reconstructions to understand the relationship between larval habitat productivity and oviposition behaviour in Kenyan Anopheles arabiensis

BackgroundStrategies for combatting residual malaria by targeting vectors outdoors are gaining importance as the limitations of primary indoor interventions are reached. Strategies to target ovipositing females or her offspring are broadly applicable because all mosquitoes require aquatic habitats for immature development irrespective of their biting or resting preferences. Oviposition site selection by gravid females is frequently studied by counting early instar larvae in habitats; an approach which is valid only if the number of larvae correlates with the number of females laying eggs. This hypothesis was tested against the alternative, that a higher abundance of larvae results from improved survival of a similar or fewer number of families.MethodsIn a controlled experiment, 20 outdoor artificial ponds were left uncovered for 4 days to allow oviposition by wild mosquitoes, then covered with netting and first and second instar larvae sampled daily. Natural Anopheles habitats of two different types were also identified, and all visible larvae sampled. All larvae were identified to species, and most samples of the predominant species, Anopheles arabiensis, were genotyped using microsatellites for sibling group reconstructions using two contrasting softwares, BAPS and COLONY.ResultsIn the ponds, the number of families reconstructed by each software significantly predicted larval abundance (BAPS R2 = 0.318, p = 0.01; COLONY R2 = 0.476, p = 0.001), and suggested that around 50% of females spread larvae across multiple ponds (skip oviposition). From natural habitats, the mean family size again predicted larval abundance using BAPS (R2 = 0.829, p = 0.017) though not using COLONY (R2 = 0.218, p = 0.68), but both softwares once more suggested high rates of skip oviposition (in excess of 50%).ConclusionThis study shows that, whether in closely-located artificial habitats or natural breeding sites, higher early instar larval densities result from more females laying eggs in these sites. These results provide empirical support for use of early instar larval abundance as an index for oviposition site preference. Furthermore, the sharing of habitats by multiple females and the high skip-oviposition rate in An. arabiensis suggest that larviciding by auto-dissemination of insecticide may be successful.

Life Histories and Other Biological Characteristics Enabling the Establishment of Aedes albopictus in the San Gabriel Valley, California.

Since Aedes albopictus was discovered in 2011 in the San Gabriel Valley it has become widespread despite the "harsh" environmental conditions and intense efforts to control or eliminate it. Species introduced into a new area may survive, thrive, or disappear depending on whether its new environment is suitable. The San Gabriel Valley Mosquito and Vector Control District expended considerable resources from 2011 to 2015 to eradicate this invasive species or, at a minimum, control and manage its spread. Despite the intense effort, the distribution of Ae. albopictus steadily expanded. Over those 5 years this increase shifted from a geometric to exponential pattern. What enabled Ae. albopictus to survive initially, become established, and then expand their distribution when ecological conditions in southern California were considered hostile for this invasive species? This study explores several biological characteristics including skip oviposition, installment egg hatching, and variable larval development that may have helped Ae. albopictus flourish in its new environment.

Evaluation of Pyriproxyfen Dissemination via Aedes albopictus From a Point-Source Larvicide Application in Northeast Florida.

The Asian tiger mosquito, Aedes albopictus , ranks among the most important vectors of dengue fever, Zika virus, and chikungunya virus. With no specific medications or vaccines available, vector control is the only way to combat these diseases. Autodissemination of the insect growth regulator pyriproxyfen (NyGuard®) from a point-source treatment was evaluated in field settings in northeast Florida. The objective of this study was to investigate the possibility of pyriproxyfen dissemination from a treatment site to nontreated oviposition sites via the skip oviposition behavior of Ae. albopictus. A spray application was made to a tire pile using a Stihl® SR 420 backpack sprayer. Autodissemination oviposition vases containing oak infusion water were positioned in groups of five at 25 to 400 m in 4 transects surrounding the tire pile. Two sets of 5 control vases containing oak infusion water were placed 1,500 m from the tire pile and oak infusion water samples were collected directly from the tire pile. Fifty milliliter samples were extracted from each vase weekly and preserved for pyriproxyfen residue analysis. All vases were analyzed at week 0 (4 h post-treatment), 1, 2, 4, and 6. Overall, there were no differences in pupal mortality between the control and autodissemination vases. The tire pile samples had significantly more mortality (P < 0.0001) out to 4 wk when compared to autodissemination and control vases.

Control of Urban Zika Vectors: Should We Return to the Successful PAHO/WHO Strategy?

Control of Urban Zika Vectors: Should We Return to the Successful PAHO/WHO Strategy?

The Effects of Larval Habitat Quality on Aedes albopictus Skip Oviposition.

Aedes albopictus is an invasive mosquito species that transmits human-disease-causing pathogens. It is a container-inhabiting species that oviposits in resource-limited habitats. To mitigate larval competition, Ae. albopictus females may choose to distribute eggs from a single gonotrophic cycle among multiple containers through skip oviposition. With the use of individual females released in indoor and outdoor caged trials, we evaluated the oviposition choices made by gravid Ae. albopictus offered larval habitats with different qualities. Our results demonstrate that Ae. albopictus performs skip oviposition and that the degree of egg distribution is related to the quality of the larval habitat. In a 4-choice arena, individual Ae. albopictus oviposited in fewer containers when presented with ovisites of high-quality larval habitat (uncrowded conditions) compared with oviposition in low-quality (crowded conditions) larval habitats. Additionally, the females selectively oviposited in high-quality habitats when offered both low- and high-quality habitats, but distributed eggs more evenly among multiple high-quality habitats. Our results have important implications for mosquito management plans that include the use of lethal ovitraps, as well as the role of this behavior in distribution of disease-causing pathogens.

Oviposition by Aedes aegypti and Aedes albopictus: influence of congeners and of oviposition site characteristics.

We investigated the oviposition behavior of Ae. aegypti and Ae. albopictus. In particular we examined whether small-scale site characteristics and the presence of conspecifics or congeners altered oviposition by these mosquitoes. Various combinations of females of the two species were allowed to oviposit inside cages among either vegetation (potted plants) or structural components (wood and concrete blocks). Numbers of eggs deposited per female were compared between species, sides, and treatments. Most significant differences between treatments and species involved differences between single species and mixed species treatments. Ae. aegypti deposited more eggs/female in the vegetation side than in the structure side whereas the opposite pattern was evident for Ae. albopictus. Ae. aegypti females had higher frequency of skip oviposition than Ae. albopictus. An average of 63% of the containers in the two-species treatments contained eggs of both species, with more frequent joint occurrences observed in the treatment with three females of each species than in the treatments with one of each. Our results point to the existence of various interactions between gravid Ae. aegypti and Ae. albopictus females at or near the oviposition sites but further experimental work is necessary to fully characterize the interactions and their specific mechanisms.

Effect of body size and sugar meals on oviposition of the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae)

Effect of body size and sugar meals on oviposition of the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae)

Aspects of nutrition and oviposition in the endemic rockpool mosquito Opifex fuscus Hutton (Diptera: Culicidae)

Opifex fuscus is a New Zealand endemic coastal species of mosquito. It has primitive taxonomic characteristics making it an interesting species from both ecological and evolutionary perspectives, although there is limited information available on its biology. This preliminary investigation examines evidence for a link between autogenous oviposition and adult nutrition, with some observations on longevity. Our data indicate that only sugar-fed adult females are capable of laying their fi rst batch of eggs autogenously. This species was also observed to exhibit skip oviposition in the laboratory. Females fed sugar and laying eggs survived markedly longer than both females fed sugar and not laying eggs, and females not fed sugar.

Oviposition, Dispersal, and Survival in Aedes aegypti: Implications for the Efficacy of Control Strategies

There is compelling evidence that Aedes aegypti distributes small numbers of eggs among many sites, and that this "skip oviposition" is a driver for dispersal. The behavior is compatible with published results of mark-release-recapture studies, although many of these have been interpreted as evidence for limited dispersal. Skip oviposition also extends the duration of the gonotrophic cycle, the key parameter in the use of parous rates to estimate physiologic age. In addition, contact with multiple oviposition sites was probably a factor in the remarkable success of "perifocal" treatments with DDT in the campaign to eradicate Ae. aegypti from the Americas and the mobility of the vector probably limits the efficacy of attempts to suppress dengue transmission by source reduction and "focal" treatments with aerosols. Innovative approaches that exploit or negate this behavior may be required before effective Ae. aegypti control can become a reality.

Natural skip oviposition of the mosquito Aedes aegypti indicated by codominant genetic markers.

This study examines the use of codominant restriction fragment length polymorphism (RFLP) markers to estimate the number of sibling families found within and among oviposition sites used by the mosquito Aedes aegypti (L) (Diptera: Culicidae). Estimates were made using pairwise relatedness (rxy) calculations based on alleles shared between individuals. Genotypes for eight laboratory mosquito families were determined at six RFLP loci and the observed allele frequencies were used to generate simulated distributions of rxy from full-sibling and unrelated pairs of individuals. The midpoint (mp) between the means of the pairwise rxy distributions was used to discriminate full-sibling families from unrelated families. Clusters of individuals with rxy values higher than the mp value were grouped as putative sibling families. This method was tested by calculating actual rxy for all pairwise comparisons of the known laboratory full-sibling and paternal half-sibling families, followed by upgma cluster analysis to group sibling families. The technique was then used for sibling estimations on wild caught mosquitoes collected at three locations in Trinidad, West Indies. From field populations, 35 families were estimated among 122 individuals tested with an average of 6.2 families per container. Members of 19 predicted families clustered as groups across multiple containers, providing molecular evidence for skip-oviposition behaviour in Ae. aegypti females, whereby individual females oviposit in more than one container.

Indirect evidence against delayed "skip-oviposition" behavior by Aedes aegypti (Diptera: Culicidae) in Thailand.

Mosquitoes that do not oviposit their entire batch of eggs in one location, but choose instead to oviposit a few eggs in several different sites exhibit skip oviposition. Although skip oviposition may ensure the greater distribution of progeny from an individual female and reduce sibling competition, it also uses greater maternal energy reserves, may increase the risk of adult female mortality and does not reduce other competition. To test the hypothesis that female Aedes aegypti (L.) do not oviposit all of their eggs at one time and place, we examined females collected with an aspirator resting inside houses in Thailand. Females (n = 384) were dissected and the stage and number of developing oocytes were enumerated. If skip oviposition is a common behavior among female Ae. aegypti, one would expect to find significantly fewer mature eggs (Christophers' stage V) in gravid females than developing oocytes in half-gravid females (Christophers' stage IIIa-IVb). No significant differences were found between ovaries containing immature or mature oocytes, even when the data were stratified by female body size and when immature oocytes that potentially could undergo resorption (Christophers' stages IIIa-IIIb) were excluded from the analysis. We found no evidence that skip oviposition over several days is a common behavior among domestic populations of Ae. aegypti at the end of the rainy season in this region of Thailand.

An improved method for detecting substrate preferences shown by mosquitoes that exhibit ‘skip oviposition’

Abstract. A new method is described for detecting and characterizing ovi‐position‐substrate preferences among insects (e.g. Aedes aegypti) that customarily disperse the eggs of a single batch among several sites (i.e. that exhibit ‘skip oviposition’). The method entails recording the distribution of eggs by individual females provided initially with an array of identical sites, thus eliminating possible effects of position preference and female density, and then placing one test site into the array. A preferred substrate can be identified promptly in this way without having to count eggs.