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1. Not all mosquitoes are created equal: A synthesis of vector competence experiments reinforces virus associations of Australian mosquitoes

   https://doi.org/10.1371/journal.pntd.0010768  

   Kain, Morgan P. ; Skinner, Eloise B. ; Athni, Tejas S. ; Ramirez, Ana L. ; Mordecai, Erin A. ; van den Hurk, Andrew F. ( October 2022 , PLOS Neglected Tropical Diseases)

   Brackney, Doug E. (Ed.)

   The globalization of mosquito-borne arboviral diseases has placed more than half of the human population at risk. Understanding arbovirus ecology, including the role individual mosquito species play in virus transmission cycles, is critical for limiting disease. Canonical virus-vector groupings, such as Aedes - or Culex -associated flaviviruses, have historically been defined using virus detection in field-collected mosquitoes, mosquito feeding patterns, and vector competence, which quantifies the intrinsic ability of a mosquito to become infected with and transmit a virus during a subsequent blood feed. Herein, we quantitatively synthesize data from 68 laboratory-based vector competence studies of 111 mosquito-virus pairings of Australian mosquito species and viruses of public health concern to further substantiate existing canonical vector-virus groupings and quantify variation within these groupings. Our synthesis reinforces current canonical vector-virus groupings but reveals substantial variation within them. While Aedes species were generally the most competent vectors of canonical “ Aedes -associated flaviviruses” (such as dengue, Zika, and yellow fever viruses), there are some notable exceptions; for example, Aedes notoscriptus is an incompetent vector of dengue viruses. Culex spp. were the most competent vectors of many traditionally Culex -associated flaviviruses including West Nile, Japanese encephalitis and Murray Valley encephalitis viruses, although some Aedes spp. are also moderately competent vectors of these viruses. Conversely, many different mosquito genera were associated with the transmission of the arthritogenic alphaviruses, Ross River, Barmah Forest, and chikungunya viruses. We also confirm that vector competence is impacted by multiple barriers to infection and transmission within the mesenteron and salivary glands of the mosquito. Although these barriers represent important bottlenecks, species that were susceptible to infection with a virus were often likely to transmit it. Importantly, this synthesis provides essential information on what species need to be targeted in mosquito control programs. 

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2. Interspecies microbiome transplantation recapitulates microbial acquisition in mosquitoes

   https://doi.org/10.1186/s40168-022-01256-5  

   Coon, Kerri L. ; Hegde, Shivanand ; Hughes, Grant L. ( April 2022 , Microbiome)

   Mosquitoes harbor microbial communities that play important roles in their growth, survival, reproduction, and ability to transmit human pathogens. Microbiome transplantation approaches are often used to study host-microbe interactions and identify microbial taxa and assemblages associated with health or disease. However, no such approaches have been developed to manipulate the microbiota of mosquitoes.

   Here, we developed an approach to transfer entire microbial communities between mosquito cohorts. We undertook transfers between (Culex quinquefasciatustoAedes aegypti) and within (Ae. aegyptitoAe. aegypti) species to validate the approach and determine the number of mosquitoes required to prepare donor microbiota. After the transfer, we monitored mosquito development and microbiota dynamics throughout the life cycle. Typical holometabolous lifestyle-related microbiota structures were observed, with higher dynamics of microbial structures in larval stages, including the larval water, and less diversity in adults. Microbiota diversity in recipient adults was also more similar to the microbiota diversity in donor adults.

   This study provides the first evidence for successful microbiome transplantation in mosquitoes. Our results highlight the value of such methods for studying mosquito-microbe interactions and lay the foundation for future studies to elucidate the factors underlying microbiota acquisition, assembly, and function in mosquitoes under controlled conditions.

    

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3. Predation differentially structures immature mosquito populations in stormwater ponds

   https://doi.org/10.1111/een.12783  

   Holmes, Christopher J. ; Cáceres, Carla E. ( July 2019 , Ecological Entomology)

   1. Understanding the factors underlying the abundance and distribution of species requires the consideration of a complex suite of interacting biotic and abiotic factors operating on multiple spatial and temporal scales. Larval mosquitoes inhabiting small human‐constructed ponds represent a unique opportunity to investigate the relative importance of these structuring mechanisms while simultaneously generating applied knowledge on mosquito control.

   2. A multi‐year field survey of 32 stormwater ponds was conducted in central Illinois (Champaign County). From each pond, data were collected on pond structure type and hydroperiod, the presence/absence of cattails (Typhaspp.), and measures of total nitrogen, phosphorus, and organic carbon, and chlorophylla. The communities of crustacean zooplankton and aquatic insects were characterised, and these taxa were assigned into two main groups: predators and competitors of larval mosquitoes. Structural equation modelling was used to explore the direct and indirect effects of these biotic and abiotic factors on larval density for three species of culicine mosquitoes (Culex pipiens,Culex restuans, andAedes vexans).

   3. Hydroperiod had an indirect negative effect onC. pipiensdensity. However, this effect was mediated by predator density; more permanent ponds had more predators, which therefore reduced the density ofC. pipienslarvae.Aedes vexansdensity was positively correlated with predator density. No predictor variables were found that explained variation inC. restuansdensity.

   4. This study show that the relative importance of these biotic and abiotic factors varies among species of culicine mosquitoes inhabiting stormwater ponds.

    

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4. Sustained Drought, but Not Short-Term Warming, Alters the Gut Microbiomes of Wild Anolis Lizards

   https://doi.org/10.1128/aem.00530-22  

   Williams, Claire E. ; Kueneman, Jordan G. ; Nicholson, Daniel J. ; Rosso, Adam A. ; Folfas, Edita ; Casement, Brianna ; Gallegos-Koyner, Maria A. ; Neel, Lauren K. ; Curlis, John David ; McMillan, W. Owen ; et al ( October 2022 , Applied and Environmental Microbiology)

   Rudi, Knut (Ed.)

   ABSTRACT As rising temperatures threaten biodiversity across the globe, tropical ectotherms are thought to be particularly vulnerable due to their narrow thermal tolerance ranges. Nevertheless, physiology-based models highlighting the vulnerability of tropical organisms rarely consider the contributions of their gut microbiota, even though microbiomes influence numerous host traits, including thermal tolerance. We combined field and lab experiments to understand the response of the slender anole lizard ( Anolis apletophallus ) gut microbiome to climatic shifts of various magnitude and duration. First, to examine the effects of long-term climate warming in the wild, we transplanted lizards from the mainland Panama to a series of warmer islands in the Panama Canal and compared their gut microbiome compositions after three generations of divergence. Next, we mimicked the effects of a short-term “heat-wave” by using a greenhouse experiment and explored the link between gut microbiome composition and lizard thermal physiology. Finally, we examined variation in gut microbiomes in our mainland population in the years both before and after a naturally occurring drought. Our results suggest that slender anole microbiomes are surprisingly resilient to short-term warming. However, both the taxonomic and predicted functional compositions of the gut microbiome varied by sampling year across all sites, suggesting that the drought may have had a regional effect. We provide evidence that short-term heat waves may not substantially affect the gut microbiota, while more sustained climate anomalies may have effects at broad geographic scales. IMPORTANCE As climate change progresses, it is crucial to understand how animals will respond to shifts in their local environments. One component of this response involves changes in the microbial communities living in and on host organisms. These “microbiomes” can affect many processes that contribute to host health and survival, yet few studies have measured changes in the microbiomes of wild organisms experiencing novel climatic conditions. We examined the effects of shifting climates on the gut microbiome of the slender anole lizard ( Anolis apletophallus ) by using a combination of field and laboratory studies, including transplants to warm islands in the Panama Canal. We found that slender anole microbiomes remain stable in response to short-term warming but may be sensitive to sustained climate anomalies, such as droughts. We discuss the significance of these findings for a species that is considered highly vulnerable to climate change. 

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5. Transcriptional response of individual Hawaiian Culex quinquefasciatus mosquitoes to the avian malaria parasite Plasmodium relictum

   https://doi.org/10.1186/s12936-022-04271-x  

   Ferreira, Francisco C. ; Videvall, Elin ; Seidl, Christa M. ; Wagner, Nicole E. ; Kilpatrick, A. Marm ; Fleischer, Robert C. ; Fonseca, Dina M. ( August 2022 , Malaria Journal)

   Plasmodiumparasites that cause bird malaria occur in all continents except Antarctica and are primarily transmitted by mosquitoes in the genusCulex.Culex quinquefasciatus, the mosquito vector of avian malaria in Hawaiʻi, became established in the islands in the 1820s. While the deadly effects of malaria on endemic bird species have been documented for many decades, vector-parasite interactions in avian malaria systems are relatively understudied.

   To evaluate the gene expression response of mosquitoes exposed to aPlasmodiuminfection intensity known to occur naturally in Hawaiʻi, offspring of wild-collected HawaiianCx. quinquefasciatuswere fed on a domestic canary infected with a fresh isolate ofPlasmodium relictumGRW4 from a wild-caught Hawaiian honeycreeper. Control mosquitoes were fed on an uninfected canary. Transcriptomes of five infected and three uninfected individual mosquitoes were sequenced at each of three stages of the parasite life cycle: 24 h post feeding (hpf) during ookinete invasion; 5 days post feeding (dpf) when oocysts are developing; 10 dpf when sporozoites are released and invade the salivary glands.

   Differential gene expression analyses showed that during ookinete invasion (24 hpf), genes related to oxidoreductase activity and galactose catabolism had lower expression levels in infected mosquitoes compared to controls. Oocyst development (5 dpf) was associated with reduced expression of a gene with a predicted innate immune function. At 10 dpf, infected mosquitoes had reduced expression levels of a serine protease inhibitor, and further studies should assess its role as aPlasmodiumagonist inC. quinquefasciatus. Overall, the differential gene expression response of HawaiianCulexexposed to aPlasmodiuminfection intensity known to occur naturally in Hawaiʻi was low, but more pronounced during ookinete invasion.

   This is the first analysis of the transcriptional responses of vectors to malaria parasites in non-mammalian systems. Interestingly, few similarities were found between the response ofCulexinfected with a birdPlasmodiumand those reported inAnophelesinfected with humanPlasmodium. The relatively small transcriptional changes observed in mosquito genes related to immune response and nutrient metabolism support conclusions of low fitness costs often documented in experimental challenges ofCulexwith avianPlasmodium.

    

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