How micronutrients influence the physiology of mosquitoes

A machine-learning approach to optimize nutritional properties and organic wastes recycling efficiency conversed by black soldier fly (Hermetia illucens)

Suboptimal nutrition in organic waste limits the growth of black soldier fly (BSF) larvae, thereby reducing biowaste recycling efficiency. In this study, weight gain data from BSF larvae fed diets with distinct nutrient compositions were used to build a machine learning model. Among the algorithms tested, the XGBoost model demonstrated the best performance in predicting weight gain. The model identified protein as the most critical nutrient factor for larval biomass and was used to determine the optimal diet by calculating the highest weight gain from 30,000 randomly generated nutrient combinations. Supplementing the missing nutrients in organic waste according to the optimal diet improved the weight gain and feed conversion rate of BSF larvae. Feeding larvae a mixture of organic wastes, a cost-effective strategy to meet dietary nutrition requirements, resulted in significant increases in both the bioconversion rate (up to 9.7%) and mass reduction rate (up to 22.8%) of organic waste.

Knockdown of the adipokinetic hormone receptor inhibits the reproduction of female Culex pipiens pallens (Diptera: Culicidae) by downregulating L-homoserine and serotonin levels

The adipokinetic hormone (AKH) receptor, interacting with AKH, regulates the metabolism of amino acids, carbohydrates, and lipids. The AKH receptor is abundant in mosquito primary and secondary sexual organs; however, the exact role of the AKH receptor in mosquito reproductive processes and the specific mechanisms involved are unclear. Among different tissues of adult female mosquitoes (Culex pipiens pallens), the ovaries and fat body showed high expression of the AKH receptor gene. Silencing this gene led to anti-reproductive effects, including abnormal ovarian morphology, reduced follicle number, and a decreased egg-laying count. Meanwhile, decreased yolk accumulation and iron deposition in the ovaries during the vitellogenesis phase were observed, accompanied by reduced expression levels of the vitellogenin-A1 precursor gene and transferrin gene. Liquid chromatography-mass spectrometry analysis revealed a decrease in L-homoserine and serotonin levels following AKH receptor gene knockdown, and supplementation with the above 2 metabolites partly rescued the anti-reproductive phenotype and increased the expression of the vitellogenin-A1 precursor gene and transferrin gene in the AKH receptor gene knockdown mosquitoes. Consistent with the gene knockdown results, Relugolix, an inhibitor of this receptor, likewise affected egg production. Herein, we revealed evidence for the function and potential mechanism of the AKH receptor during female mosquito reproduction, possibly offering an alternative method to control mosquitoes.

Identifying mosquito plant hosts from ingested nectar secondary metabolites

Establishing how plants contribute food and refuge to insects can be challenging for small species that are difficult to observe in their natural habitat, such as disease vectoring mosquitoes. Currently indirect methods of plant-host identification rely on DNA sequencing of ingested plant material but are often unsuccessful for small insects that feed primarily on plant sugars or have little contact with plant cells. Here we developed an innovative approach to determine species-specific phytophagy by detecting taxon-specific plant secondary metabolites (PSMs) in nectar. Two mosquito species were exposed to three PSMs, each present in the nectar of a known plant host, firstly from dosed sucrose solutions and secondly from flowers. Both experiments yielded high rates of PSM detection in mosquitoes using liquid chromatography-mass spectrometry (LC-MS). PSMs were consistently detected in mosquitoes up to 8 h post-ingestion. In experiments consisting of two or three plant species, multiple PSMs from different host plants could be detected. These positive results demonstrate that PSMs could be useful indicators of insect plant-hosts selection in the wild. With expanded knowledge of nectar-based PSMs across a landscape, improved knowledge of plant-host relationships could be achieved where direct observations in their natural habitat are lacking. Increasing understanding of vector insect ecology will have an important role in tackling vector-borne disease.

Exposure to copper metal enhances the tolerance of An. gambiae s.s. over multiple generations while reducing both fertility and fecundity in this primary malaria vector

Background

Anopheles s.l. displays the potential to develop tolerance to heavy metals, particularly copper, this may occur at a significant biological cost, which can adversely affect its ecological fitness. This study investigated the larval metal exposure on larval development and reproduction of An. gambiae s.s., a laboratory susceptible strain, kisumu.

Methods

Stage 2 larvae of Anopheles gambiae, Kisumu were exposed to C 1 = 484 μg L -1, C 2 = 300 μg L -1 and 0 μg L -1 (control) of copper chloride. Larval mortality, pupation time, pupation rate, gonotrophic cycle length, fecundity and fertility of larvae/adults were assessed over six generations.

Results

Results revealed that larval mortality rate was significantly higher in the C 1 groups of each group (p = 0.000), but this mortality rate decreased over generations. Pupation time was extended to 13 and 14 days respectively for C 2 and C 1 groups (p = 0.000) compared to the control group. Similar results were observed for the gonotrophic cycle, which increased from 4 days at G0 to more than 6 days at generation 5 in adults of C 1. The pupation rate in generation 4 (C 1) and generation 5 of the same group (p = 0.000) as well as the emergence rate in generation 4 (C 2, p = 0.000) and generation 5 (C 1 and C 2, p = 0.000) decreased significantly compared to the control group. The average number of eggs laid was lower in the test groups from generation 4 to generation 5 (C 1 and C 2, p = 0.00) and egg fertility was also negatively affected by exposure of the larval stage of An. gambiae s.s. to copper.

Conclusion

This study showed that copper not only exhibits larvicidal properties in Anopheles gambiae s.s. larvae, it also revealed the potential of this metal to reduce fecundity and fertility in these malaria vectors.

Mosquitoes feeding on ectothermic hosts: from host seeking to pathogen transmission

While much research has centered on mosquitoes transmitting pathogens to mammals and birds, several species feed on cold-blooded hosts, including amphibians, reptiles, fish, and various invertebrates. Despite limited knowledge about these alternative feeding habits, delving into their biology offers valuable insights into the evolutionary origins of blood feeding and aids in developing comprehensive epidemiological models for vector-borne diseases. This review sheds light on these 'alternative' hosts, highlighting recent discoveries in this field and probing into the evolutionary theories surrounding blood feeding in mosquitoes. Additionally, we delve into the host-seeking cues used by ectotherm-feeding mosquitoes and the physiological and mechanical challenges inherent in feeding on cold-blooded animals, contrasting them with endotherm-feeding mosquitoes. Finally, we examine the pathogens these mosquitoes can transmit. While our understanding of mosquitoes with alternative hosts remains incomplete, this review synthesizes existing knowledge, offering insights into the biology and ecology of mosquito species that target cold-blooded hosts.

Soil-plant-gall relationships: from gall development to ecological patterns

The adaptive nature of the galler habit has been tentatively explained by the nutrition, microenvironment, and enemy hypotheses. Soil attributes have direct relationships with these three hypotheses at the cellular and macroecological scales, but their influence has been restricted previously to effects on the nutritional status of the host plant on gall richness and abundance. Herein, we discuss the ionome patterns within gall tissues and their significance for gall development, physiology, structure, and for the nutrition of the gallers. Previous ecological and chemical quantification focused extensively on nitrogen and carbon contents, evoking the carbon-nutrient defence hypothesis as an explanation for establishing the plant-gall interaction. Different elements are involved in cell wall composition dynamics, antioxidant activity, and regulation of plant-gall water dynamics. An overview of the different soil-plant-gall relationships highlights the complexity of the nutritional requirements of gallers, which are strongly influenced by environmental soil traits. Soil and plant chemical profiles interact to determine the outcome of plant-herbivore interactions and need to be addressed by considering not only the soil features and galler nutrition but also the host plant's physiological traits. The quantitative and qualitative results for iron metabolism in gall tissues, as well as the roles of iron as an essential element in the physiology and reproduction of gallers suggest that it may represent a key nutritional resource, aligning with the nutrition hypothesis, and providing an integrative explanation for higher gall diversity in iron-rich soils.

In situ detection of ferric reductase activity in the intestinal lumen of an insect

The rise of atmospheric oxygen as a result of photosynthesis in cyanobacteria and chloroplasts has transformed most environmental iron into the ferric state. In contrast, cells within organisms maintain a reducing internal milieu and utilize predominantly ferrous iron. Ferric reductases are enzymes that transfer electrons to ferric ions, either extracellularly or within endocytic vesicles, enabling cellular ferrous iron uptake through Divalent Metal Transporter 1. In mammals, duodenal cytochrome b is a ferric reductase of the intestinal epithelium, but how insects reduce and absorb dietary iron remains unknown. Here we provide indirect evidence of extracellular ferric reductase activity in a small subset of Drosophila melanogaster intestinal epithelial cells, positioned at the neck of the midgut's anterior region. Dietary-supplemented bathophenanthroline sulphate (BPS) captures locally generated ferrous iron and precipitates into pink granules, whose chemical identity was probed combining in situ X-ray absorption near edge structure and electron paramagnetic resonance spectroscopies. An increased presence of manganese ions upon BPS feeding was also found. Control animals were fed with ferric ammonium citrate, which is accumulated into ferritin iron in distinct intestinal subregions suggesting iron trafficking between different cells inside the animal. Spectroscopic signals from the biological samples were compared to purified Drosophila and horse spleen ferritin and to chemically synthesized BPS-iron and BPS-manganese complexes. The results corroborated the presence of BPS-iron in a newly identified ferric iron reductase region of the intestine, which we propose constitutes the major site of iron absorption in this organism.

Extrinsic and intrinsic regulation of blood feeding in mosquitoes

Mosquitoes obtain large amounts of blood from hosts in a short period of time. To efficiently obtain high-quality blood without being noticed by the host, mosquitoes sense external factors such as the taste of the host blood and the surrounding environment, and integrate these signals with their own internal information to determine whether to initiate blood feeding and how long to continue feeding. With the development of gene editing and behavior monitoring techniques, the factors that control blood feeding are being identified. Elucidating the factors that contribute to blood feeding is expected to provide new ideas for artificially controlling blood feeding, which has often been overlooked behind host attraction mechanisms. Furthermore, understanding salivary components, mechanisms controlling satiety in feeding, and differences between sugar feeding and blood feeding would help us understand how some mosquitoes have adopted and developed blood feeding over the course of evolution.

Fibrinopeptide A-induced blood-feeding arrest in the yellow fever mosquito Aedes aegypti

Female mosquitoes engage in blood feeding from their hosts to facilitate egg maturation but cease feeding once a sufficient blood meal has been acquired. Abdominal distention has been proposed as a contributing factor; however, it has also been suggested that there are chemical controls. In this study, we focus on negative chemical regulators of blood feeding, particularly those present in the host blood. Serum derived from animal blood inhibits the feeding of ATP, a phagostimulant of blood feeding in Aedes aegypti. Fibrinopeptide A (FPA), a 16-amino acid peptide cleaved from fibrinogen during blood coagulation, serves as an inhibitory factor in the serum. Our findings suggest that blood-feeding arrest in female mosquitoes is triggered by the detection of FPA in the host blood, which increases as blood coagulation proceeds in the mosquito's midgut, highlighting the role of host-derived substances as negative regulators of mosquito behavior.

Morphological characterization of antennal sensilla in Toxorhynchites theobaldi, Toxorhynchites violaceus, and Lutzia bigoti adults: a comparative study using scanning electron microscopy

Some mosquitoes, including species of the genus Toxorhynchites, are known for actively preying on other mosquito larvae, making these predators valuable allies in the fight against vector-borne diseases. A comprehensive understanding of the anatomy and physiology of these potential biological control agents is helpful for the development of effective strategies for controlling vector populations. This includes the antennae, a crucial component in the search for hosts, mating, and selection of oviposition sites. This study utilized scanning electron microscopy to characterize the sensilla on the antennae of adult mosquitoes from two species that are exclusively phytophagous, including Toxorhynchites theobaldi and Toxorhynchites violaceus, as well as Lutzia bigoti, which females are allegedly hematophagous. The types of sensilla in each species were compared, and five basic types of antennal sensilla were identified: trichoid, chaetic, coeloconic, basiconic, and ampullacea. The analysis also found that they were morphologically similar across the three species, regardless of feeding habits or sex. The identification and characterization of basic types of antennal sensilla in T. theobaldi, T. violaceus, and L. bigoti suggest that these structures, which play a crucial role in the behavior and ecology, have common functions across different mosquito species, despite differences in feeding habits or sex.

Implications of mosquito metabolism on vector competence

Mosquito-borne diseases (MBDs) annually kill nearly half a million people. Due to the lack of effective vaccines and drugs on most MBDs, disease prevention relies primarily on controlling mosquitoes. Despite huge efforts having been put into mosquito control, eco-friendly and sustainable mosquito-control strategies are still lacking and urgently demanded. Most mosquito-transmitted pathogens have lost the capacity of de novo nutrition biosynthesis, and rely on their vertebrate and invertebrate hosts for sustenance during the long-term obligate parasitism process. Therefore, a better understanding of the metabolic interactions between mosquitoes and pathogens will contribute to the discovery of novel metabolic targets or regulators that lead to reduced mosquito populations or vector competence. This review summarizes the current knowledge about the effects of mosquito metabolism on the transmission of multiple pathogens. We also discuss that research in this area remains to be explored to develop multiple biological prevention and control strategies for MBDs.

Chemical ecology of nectar-mosquito interactions: recent advances and future directions

Mosquitoes, males and females, rely on sugar-rich resources, including floral nectar as a primary source of sugar to meet their energy and nutritional needs. Despite advancements in understanding mosquito host-seeking and blood-feeding preferences, significant gaps in our knowledge of the chemical ecology mediating mosquito-nectar associations remain. The influence of such association with nectar on mosquito behavior and the resulting effects on their fitness are also not totally understood. It is significant that floral nectar frequently acts as a natural habitat for various microbes (e.g. bacteria and yeast), which substantially alter nectar characteristics, influencing the nutritional ecology of flower-visiting insects, such as mosquitoes. The role of nectar-inhabiting microbes in shaping the nectar-mosquito interactions remains, however, under-researched. This review explores recent advances in understanding the role of such multitrophic interactions on the fitness and life history traits of mosquitoes and outlines future directions for research toward their control as disease vectors.

Sugar feeding by invasive mosquito species on ornamental and wild plants

Feeding on plant-derived sugars is an essential component of mosquito biology, affecting key aspects of their lives such as survival, metabolism, and reproduction. Among mosquitoes, Aedes aegypti and Aedes albopictus are two invasive mosquito species in the US, and are vectors of diseases such as dengue fever, chikungunya, and Zika. These species live in heavily populated, urban areas, where they have high accessibility to human hosts as well as to plants in backyards and public landscapes. However, the range of plants that are suitable sugar hosts for these species remains to be described, despite the importance of understanding what plants may attract or repel mosquitoes to inform citizens and municipal authorities accordingly. Here, we tested whether Ae. aegypti and Ae. albopictus would sugar-feed on eleven commonly planted ornamental plant species. We confirmed feeding activity using the anthrone method and identified the volatile composition of plant headspace using gas-chromatography mass-spectroscopy. These chemical analyses revealed that a broad range of olfactory cues are associated with plants that mosquitoes feed on. This prompted us to use plant DNA barcoding to identify plants that field-caught mosquitoes feed on. Altogether, results show that native and invasive mosquito species can exploit a broader range of plants than originally suspected, including wild and ornamental plants from different phyla throughout the Spring, Summer and Fall seasons.

Starving the Beast: Limiting Coenzyme A Biosynthesis to Prevent Disease and Transmission in Malaria

Malaria parasites must acquire all necessary nutrients from the vertebrate and mosquito hosts to successfully complete their life cycle. Failure to acquire these nutrients can limit or even block parasite development and presents a novel target for malaria control. One such essential nutrient is pantothenate, also known as vitamin B5, which the parasite cannot synthesize de novo and is required for the synthesis of coenzyme A (CoA) in the parasite. This review examines pantothenate and the CoA biosynthesis pathway in the human-mosquito-malaria parasite triad and explores possible approaches to leverage the CoA biosynthesis pathway to limit malaria parasite development in both human and mosquito hosts. This includes a discussion of sources for pantothenate for the mosquito, human, and parasite, examining the diverse strategies used by the parasite to acquire substrates for CoA synthesis across life stages and host resource pools and a discussion of drugs and alternative approaches being studied to disrupt CoA biosynthesis in the parasite. The latter includes antimalarial pantothenate analogs, known as pantothenamides, that have been developed to target this pathway during the human erythrocytic stages. In addition to these parasite-targeted drugs, we review studies of mosquito-targeted allosteric enzymatic regulators known as pantazines as an approach to limit pantothenate availability in the mosquito and subsequently deprive the parasite of this essential nutrient.

Temperature and age, individually and interactively, shape the size, weight, and body composition of adult female mosquitoes

Most insects are poikilotherms and ectotherms, so their body temperature fluctuates and closely aligns with the temperature of their environment. The rise in global temperatures is affecting the physiology of insects by altering their ability to survive, reproduce, and transmit disease. Aging also impacts insect physiology because the body deteriorates via senescence as the insect ages. Although temperature and age both impact insect biology, these factors have historically been studied in isolation. So, it is unknown whether or how temperature and age interact to shape insect physiology. Here, we investigated the effects of warmer temperature (27 °C, 30 °C and 32 °C), aging (1, 5, 10, and 15 days post-eclosion), and their interaction on the size and body composition of the mosquito, Anopheles gambiae. We found that warmer temperatures result in slightly smaller adult mosquitoes, as measured by abdomen and tibia length. Aging alters both abdominal length and dry weight in a manner that correlates with the increase in energetic resources and tissue remodeling that occurs after metamorphosis and the senescence-based decline that ensues later. Moreover, the carbohydrate and lipid contents of adult mosquitoes are not meaningfully affected by temperature but are altered by aging: carbohydrate content increases with age whereas lipid content increases over the first few days of adulthood and then decreases. Protein content decreases with both rising temperature and aging, and the aging-associated decrease accelerates at warmer temperatures. Altogether, temperature and age, individually and to a lesser extent interactively, shape the size and composition of adult mosquitoes.

Effects of bacterial composition and aquatic habitat metabolites on malaria vector larval availability in irrigated and non-irrigated sites of Homa Bay county, western Kenya

Gravid Anopheles malaria vectors depend on both chemical and physical (including microbial) cues for selection of preferred habitats for oviposition. This study focused on assessing the effects of bacterial composition and habitat metabolites on malaria vector larval availability in irrigated and non-irrigated potential larval sources. Water samples were collected from larval positive and negative habitats in the irrigated and non- irrigated areas of Homa Bay county. Bacteria cultured from the water samples were subjected to Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) for species identification. DNA was extracted from the colonies and polymerase chain reaction (PCR) and sequencing done. Finally, the metabolite composition of larval positive and negative habitats was determined. MALDI-TOF MS results revealed that Bacillus was the only genera identified from larval sources in the non-irrigated zone. In the irrigated area, Shigella was the dominant genera (47%) while Escherichia coli was the abundant species (13/51). Of the sequenced isolates, 65% were Bacillus. Larvicidal isolates Brevibacillus brevis, Bacillus subtilis, and Exiguobacterium profundum were isolated and grouped with Bacillus mojavensis, Bacillus tequilensis, Bacillus stercoris, and Brevibacillus agri. Irrigated areas with larvae had reduced crude fat (0.01%) and protein content (0.13%) in comparison to those without larvae. In irrigated and non- irrigated areas, larval presence was evident in habitats with high total chlorophyll content (1.12 μg/g vs 0.81μg/g and 3.37 μg/g vs 0.82). Aquatic habitats with larvae in both irrigated and non-irrigated areas exhibited higher sugar concentration than habitats without larvae; however, when compared, non-irrigated areas with larvae had higher sugar concentration than similar habitats in irrigated areas. In addition, substantial concentrations of Manganese, Calcium, and Copper were found in aquatic habitats containing larvae in both irrigated and non-irrigated areas. These results allow for prospective examination as potential larvicidal or adulticidal agents and could be considered when designing potential vector control interventions.

The buzz in the field: the interaction between viruses, mosquitoes, and metabolism

Among many medically important pathogens, arboviruses like dengue, Zika and chikungunya cause severe health and economic burdens especially in developing countries. These viruses are primarily vectored by mosquitoes. Having surmounted geographical barriers and threat of control strategies, these vectors continue to conquer many areas of the globe exposing more than half of the world's population to these viruses. Unfortunately, no medical interventions have been capable so far to produce successful vaccines or antivirals against many of these viruses. Thus, vector control remains the fundamental strategy to prevent disease transmission. The long-established understanding regarding the replication of these viruses is that they reshape both human and mosquito host cellular membranes upon infection for their replicative benefit. This leads to or is a result of significant alterations in lipid metabolism. Metabolism involves complex chemical reactions in the body that are essential for general physiological functions and survival of an organism. Finely tuned metabolic homeostases are maintained in healthy organisms. However, a simple stimulus like a viral infection can alter this homeostatic landscape driving considerable phenotypic change. Better comprehension of these mechanisms can serve as innovative control strategies against these vectors and viruses. Here, we review the metabolic basis of fundamental mosquito biology and virus-vector interactions. The cited work provides compelling evidence that targeting metabolism can be a paradigm shift and provide potent tools for vector control as well as tools to answer many unresolved questions and gaps in the field of arbovirology.

Metal ions in insect reproduction: a crosstalk between reproductive physiology and immunity

Most insects exhibit high reproductive capacity, which demands large amounts of energy, including macronutrients and micronutrients. Interestingly, many proteins involved in oogenesis depend on metals ions, in particular iron (Fe), zinc (Zn), and copper (Cu). Mechanisms by which metal ions influence reproduction have been described in Drosophila melanogaster, but remain poorly understood in hematophagous insects where blood meals include significant ingestion of metal ions. Moreover, there is evidence that some proteins involved in reproduction and immunity could have dual function in both processes. This review highlights the importance of metal ions in the reproduction of non-hematophagous and hematophagous insects. In addition, we discuss how insects optimize physiological processes using proteins involved in crosstalk between reproductive physiology and immunity, which is a double-edge sword in allocating their functions to protect the insect and ensure reproduction.

Functional disruption of transferrin expression alters reproductive physiology in Anopheles culicifacies

BACKGROUND

Iron metabolism is crucial to maintain optimal physiological homeostasis of every organism and any alteration of the iron concentration (i.e. deficit or excess) can have adverse consequences. Transferrins are glycoproteins that play important role in iron transportation and have been widely characterized in vertebrates and insects, but poorly studied in blood-feeding mosquitoes.

RESULTS

We characterized a 2102 bp long transcript AcTrf1a with complete CDS of 1872bp, and 226bp UTR region, encoding putative transferrin homolog protein from mosquito An. culicifacies. A detailed in silico analysis predicts AcTrf1a encodes 624 amino acid (aa) long polypeptide that carries transferrin domain. AcTrf1a also showed a putative N-linked glycosylation site, a characteristic feature of most of the mammalian transferrins and certain non-blood feeding insects. Structure modelling prediction confirms the presence of an iron-binding site at the N-terminal lobe of the transferrin. Our spatial and temporal expression analysis under altered pathophysiological conditions showed that AcTrf1a is abundantly expressed in the fat-body, ovary, and its response is significantly altered (enhanced) after blood meal uptake, and exogenous bacterial challenge. Additionally, non-heme iron supplementation of FeCl3 at 1 mM concentration not only augmented the AcTrf1a transcript expression in fat-body but also enhanced the reproductive fecundity of gravid adult female mosquitoes. RNAi-mediated knockdown of AcTrf1a causes a significant reduction in fecundity, confirming the important role of transferrin in oocyte maturation.

CONCLUSION

All together our results advocate that detailed characterization of newly identified AcTrf1a transcript may help to select it as a unique target to impair the mosquito reproductive outcome.

Shotgun and TMT-Labeled Proteomic Analysis of the Ovarian Proteins of an Insect Vector, Aedes aegypti (Diptera: Culicidae)

Aedes aegypti [Linnaeus in Hasselquist; yellow fever mosquito] transmits several viruses that infect millions of people each year, including Zika, dengue, yellow fever, chikungunya, and West Nile. Pathogen transmission occurs during blood feeding. Only the females blood feed as they require a bloodmeal for oogenesis; in the bloodmeal, holo-transferrin and hemoglobin provide the females with a high iron load. We are interested in the effects of the bloodmeal on the expression of iron-associated proteins in oogenesis. Previous data showed that following digestion of a bloodmeal, ovarian iron concentrations doubles by 72 hr. We have used shotgun proteomics to identify proteins expressed in Ae. aegypti ovaries at two oogenesis developmental stages following blood feeding, and tandem mass tag-labeling proteomics to quantify proteins expressed at one stage following feeding of a controlled iron diet. Our findings provide the first report of mosquito ovarian protein expression in early and late oogenesis. We identify proteins differentially expressed in the two oogenesis development stages. We establish that metal-associated proteins play an important role in Ae. aegypti oogenesis and we identify new candidate proteins that might be involved in mosquito iron metabolism. Finally, this work identified a unique second ferritin light chain subunit, the first reported in any species. The shotgun proteomic data are available via ProteomeXchange with identifier PXD005893, while the tandem mass tag-labeled proteomic data are available with identifier PXD028242.

Beyond the eye: Kynurenine pathway impairment causes midgut homeostasis dysfunction and survival and reproductive costs in blood-feeding mosquitoes

Insect ommochrome biosynthesis pathways metabolize tryptophan to generate eye-color pigments and wild-type alleles of pathway genes are useful phenotypic markers in transgenesis studies. Pleiotropic effects of mutations in some genes exert a load on both survival and reproductive success in blood-feeding species. Here, we investigated the challenges imposed on mosquitoes by the increase of tryptophan metabolites resulting from blood meal digestion and the impact of disruptions of the ommochrome biosynthesis pathway. Female mosquitoes with spontaneous and induced mutations in the orthologs of the genes encoding kynurenine hydroxylase in Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus exhibited impaired survival and reproductive phenotypes that varied in type and severity among the species. A compromised midgut permeability barrier function was also observed in An. stephensi. Surprisingly, mutant mosquitoes displayed an increase in microbiota compared to controls that was not accompanied by a general induction of immune genes. Antibiotic treatment rescued some deleterious traits implicating a role for the kynurenine pathway (KP) in midgut homeostasis. Supplemental xanthurenic acid, a KP end-product, rescued lethality and limited microbiota proliferation in Ae. aegypti. These data implicate the KP in the regulation of the host/microbiota interface. These pleiotropic effects on mosquito physiology are important in the development of genetic strategies targeting vector mosquitoes.

The roles of metals in insect-microbe interactions and immunity

Metal ions play essential roles in diverse physiological processes in insects, including immunity and interactions with microbes. Some, like iron, are essential nutrients and therefore are the subject of a tug-of-war between insects and microbes. Recent findings showed that the hypoferremic response mediated by Transferrin 1 is an essential defense mechanism against pathogens in insects. Transferrin 1 and the overall iron metabolism were also implicated in mediating interactions between insects and beneficial microbes. Other metals, like copper and zinc, can interfere with insect immune effectors, and either enhance (antimicrobial peptides) or reduce (reactive oxygen species) their activity. By covering recent advances in the field, this review emphasizes the importance of metals as essential mediators of insect-microbe interactions.

Exposure to copper sulfate impairs survival, post-embryonic midgut development and reproduction in Aedes aegypti

Aedes aegypti is a vector of several global human viruses responsible for high human morbidity and mortality. The method to prevent the transmission of vector-borne viruses is mainly based on the control of the insect vector using insecticides. Among these chemicals, copper sulfate is a compound widely used in agriculture with the potential to be used as an alternative to control these insects. This study evaluated the effects of the exposure of A. aegypti larvae to copper sulfate on survival, midgut morphology, blood-feeding and fecundity. The exposure to CuSO₄ decreased the survival of A. aegypti during the immature phase. Adults obtained from exposed larvae had their lifespan decreased at all tested concentrations. The exposure to CuSO₄ impaired the development in the transition from larvae to pupae and from pupae to adult. The number of eggs laid by females developed from larvae treated with CuSO₄ was significantly lower than in control. In addition, the egg hatching rates were also negatively affected. The midguts of treated larvae and pupae showed epithelial disorganization. The number of cleaved caspase-3 cells increased in the midgut of exposed pupae compared to control. Moreover, there was a reduction in proliferating cells in treated larvae and pupae compared to the control. In conclusion, the results reveal that CuSO₄ exposure has insecticidal activity against A. aegypti, which may be related to the impairment of the midgut metamorphosis and reduced proliferation of stem cells, with the consequent impairment of female mosquito fertility and fecundity.

Characterization of a copper transporter 1 from Dermanyssus gallinae as a vaccine antigen

Poultry red mites (Dermanyssus gallinae, PRM) are dangerous ectoparasites that infest chickens and threaten the poultry industry worldwide. PRMs usually develop resistance to chemical acaricides, necessitating the development of more effective preventive agents, and vaccination could be an alternative strategy for controlling PRMs. The suitability of plasma membrane proteins expressed in the midguts as vaccine antigens was evaluated because these molecules are exposed to antibodies in the ingested blood and the binding of antibodies could potentially induce direct damage to midgut tissue and indirect damage via inhibition of the functions of target molecules. Therefore, in the present study, a copper transporter 1-like molecule (Dg-Ctr1) was identified and its efficacy as a vaccine antigen was assessed in vitro. Dg-Ctr1 mRNA was expressed in the midguts and ovaries and in all the life stages, and flow cytometric analysis indicated that Dg-Ctr1 was expressed on the plasma membrane. Importantly, nymphs fed on plasma derived from chickens immunized with the recombinant protein of the extracellular region of Dg-Ctr1 showed a significant reduction in the survival rate. These data indicate that the application of Dg-Ctr1 as a vaccine antigen could reduce the number of nymphs in the farms, contributing to reduction in the economic losses caused by PRMs in the poultry industry. To establish an effective vaccination strategy, the acaricidal effects of the combined use of Dg-Ctr1 with chemical acaricides or other vaccine antigens must be examined.

Specific phytochemicals in floral nectar up-regulate genes involved in longevity regulation and xenobiotic metabolism, extending mosquito life span

During nectar feeding, mosquitoes ingest a plethora of phytochemicals present in nectar. The ecological and physiological impacts of these ingested phytochemicals on the disease vectors are poorly understood. In this study, we evaluated the effects of three nectar phytochemicals-- caffeine, p-coumaric acid, and quercetin--on longevity, fecundity, and sugar-feeding behavior of the Asian tiger mosquito (Aedes albopictus). Adult females of Ae. albopictus were provided continuous access to 10% sucrose supplemented with one of the three phytochemicals and their fecundity, longevity, and the amount of sucrose consumed determined. Transcriptome response of Ae. albopictus females to p-coumaric acid and quercetin was also evaluated. Dietary quercetin and p-coumaric acid enhanced the longevity of female Ae. albopictus, while caffeine resulted in reduced sugar consumption and enhanced fecundity of gravid females. RNA-seq analyses identified 237 genes that were differentially expressed (DE) in mosquitoes consuming p-coumaric acid or quercetin relative to mosquitoes consuming an unamended sucrose solution diet. Among the DE genes, several encoding antioxidant enzymes, cytochrome P450s, and heat shock proteins were upregulated, whereas histones were downregulated. Overall, our findings show that consuming certain nectar phytochemicals can enhance adult longevity of female Asian tiger mosquitoes, apparently by differentially regulating the expression level of genes involved in longevity and xenobiotic metabolism; this has potential impacts not only on life span but also on vectorial capacity and insecticide resistance.

Mosquito metallomics reveal copper and iron as critical factors for Plasmodium infection

Iron and copper chelation restricts Plasmodium growth in vitro and in mammalian hosts. The parasite alters metal homeostasis in red blood cells to its favor, for example metabolizing hemoglobin to hemozoin. Metal interactions with the mosquito have not, however, been studied. Here, we describe the metallomes of Anopheles albimanus and Aedes aegypti throughout their life cycle and following a blood meal. Consistent with previous reports, we found evidence of maternal iron deposition in embryos of Ae. aegypti, but less so in An. albimanus. Sodium, potassium, iron, and copper are present at higher concentrations during larval developmental stages. Two An. albimanus phenotypes that differ in their susceptibility to Plasmodium berghei infection were studied. The susceptible white stripe (ws) phenotype was named after a dorsal white stripe apparent during larval stages 3, 4, and pupae. During larval stage 3, ws larvae accumulate more iron and copper than the resistant brown stripe (bs) phenotype counterparts. A similar increase in copper and iron accumulation was also observed in the susceptible ws, but not in the resistant bs phenotype following P. berghei infection. Feeding ws mosquitoes with extracellular iron and copper chelators before and after receiving Plasmodium-infected blood protected from infection and simultaneously affected follicular development in the case of iron chelation. Unexpectedly, the application of the iron chelator to the bs strain reverted resistance to infection. Besides a drop in iron, iron-chelated bs mosquitoes experienced a concomitant loss of copper. Thus, the effect of metal chelation on P. berghei infectivity was strain-specific.

Olfaction in Anopheles mosquitoes

As vectors of disease, mosquitoes are a global threat to human health. The Anopheles mosquito is the deadliest mosquito species as the insect vector of the malaria-causing parasite, which kills hundreds of thousands every year. These mosquitoes are reliant on their sense of smell (olfaction) to guide most of their behaviors, and a better understanding of Anopheles olfaction identifies opportunities for reducing the spread of malaria. This review takes a detailed look at Anopheles olfaction. We explore a range of topics from chemosensory receptors, olfactory neurons, and sensory appendages to behaviors guided by olfaction (including host-seeking, foraging, oviposition, and mating), to vector management strategies that target mosquito olfaction. We identify many research areas that remain to be addressed.

Social interactions upregulate hemolymph tryptophan and tyrosine levels in the male lobster cockroach

In the present study, we found that tryptophan (TRP) and tyrosine (TYR) levels are increased in hemolymph of male Nauphoeta cinerea after social contact with either male or female conspecifics. Hemolymph was collected from individual males before and after the social interactions, and samples were analyzed by HPLC-ECD; analyte identities were confirmed by UPLC/MS. After a male-male first encounter fight, hemolymph TRP and TYR levels were significantly increased in dominants compared with the levels before the encounter. Conversely, TRP and TYR in subordinates were maintained at levels similar to those before the encounter. While after-fight TRP and TYR levels were significantly higher in dominants than subordinates, no significant differences were found in the contestants before the fight. Moreover, contact with an isolated male antenna was sufficient to stimulate attack behavior and increase hemolymph TRP and TYR titers to levels similar to those seen in dominants. After a male-female interaction, two distinct outcomes could be observed. Either hemolymph TRP and TYR levels were increased in successfully mated males, or TRP and TYR levels were unchanged in males that only exhibited premating wing-raising behavior but failed in mating. After contacting the antenna of a socially naïve male with an isolated female antenna, three patterns of behavior and related amino acid response were observed: 1) only premating wing-raising behavior with significant increase of TRP and TYR levels, 2) only attack behavior with significant increase of TRP and TYR levels, and 3) mixed wing-raising and attack behaviors with no significant changes in TRP and TYR levels. The present results show a robust response of hemolymph TRP and TYR to social contact. In light of previously characterized responses in pheromone and juvenile hormone levels, these amine responses suggest that the physiological response of N. cinerea to social contact is multi-dimensional.

Plasmodium oocysts respond with dormancy to crowding and nutritional stress

Malaria parasites develop as oocysts in the mosquito for several days before they are able to infect a human host. During this time, mosquitoes take bloodmeals to replenish their nutrient and energy reserves needed for flight and reproduction. We hypothesized that these bloodmeals are critical for oocyst growth and that experimental infection protocols, typically involving a single bloodmeal at the time of infection, cause nutritional stress to the developing oocysts. Therefore, enumerating oocysts disregarding their growth and differentiation state may lead to erroneous conclusions about the efficacy of transmission blocking interventions. Here, we examine this hypothesis in Anopheles coluzzii mosquitoes infected with the human and rodent parasites Plasmodium falciparum and Plasmodium berghei, respectively. We show that oocyst growth and maturation rates decrease at late developmental stages as infection intensities increase; an effect exacerbated at very high infection intensities but fully restored with post infection bloodmeals. High infection intensities and starvation conditions reduce RNA Polymerase III activity in oocysts unless supplemental bloodmeals are provided. Our results suggest that oocysts respond to crowding and nutritional stress with a dormancy-like strategy, which urges the development of alternative methods to assess the efficacy of transmission blocking interventions.

A simple and affordable method for estimating the fluid volume a mosquito sucks using food dyes

BACKGROUND

Blood-sucking by mosquitoes is an inevitable behavior when pathogens are transmitted among humans. Adenine nucleotides such as ATP are known as phagostimulants for mosquitoes and are widely used to induce and enhance the blood-sucking activity in an artificial manner. Although using ATP solution is convenient to introduce a variety of substances (for example chemicals and pathogens) into the mosquito body via sucking, establishing an easy and cost-effective method to quantify the amount of solution ingested has yet to be reported.

RESULTS

A set of commercial food dyes (green, blue, yellow, and red) was employed in this study. Each dye was added to ATP solution used to colorize the abdomen of Ae. aegypti female mosquitoes after ingestion. The intake of food dyes did not show any toxicity to the mosquitoes, affecting neither ATP-sucking behavior nor survival of the mosquitoes. We observed that quantifying the color intensity of green dye in the mosquito abdomen by spectral analysis, as well as distinguishing the size of the colored abdomen using the naked eye, allowed the estimation of the amount of ingested solution. Using this method, capsaicin, a pungent component of chili peppers, was identified as an aversive tastant that can discourage mosquitoes from sucking the ATP solution.

CONCLUSIONS

Employing commercially available, non-toxic food dyes converted ATP-driven membrane feeding into an easy-to-use method to estimate the amount of solution ingested by mosquitoes. This method can be further applied for a variety of experiments such as introducing a certain quantity of chemical compounds or microbes into the mosquito body.

The direct and indirect effects of copper on vector-borne disease dynamics

Metal pollution is a growing concern that affects the health of humans and animals globally. Copper is an essential insect micronutrient required for respiration, pigmentation and oxidative stress protection but can also act as a potentially toxic trace element. While several studies have focused on the negative fitness effects of copper on the aquatic larvae of mosquitoes, the effects of larval copper exposure on adult mosquito fitness (i.e., survival and fecundity) and their ability to transmit parasites (i.e., vector competence) remains unclear. Here, using a well-studied model vector-parasite system, the mosquito Aedes aegypti and parasite Dirofilaria immitis, we show that sublethal copper exposure in larval mosquitoes alters adult female fecundity and vector competence. Specifically, mosquitoes exposed to copper had a hormetic fecundity response and mosquitoes exposed to 600 μg/L of copper had significantly fewer infective parasite larvae than control mosquitoes not exposed to copper. Thus, exposure of mosquito larvae to copper levels far below EPA-mandated safe drinking water limits (1300 μg/L) can impact vector-borne disease dynamics not only by reducing mosquito abundance (through increased larval mortality), but also by reducing parasite transmission risk. Our results also demonstrated that larval copper is retained through metamorphosis to adulthood in mosquitoes, indicating that these insects could transfer copper from aquatic to terrestrial foodwebs, especially in urban areas where they are abundant. To our knowledge this is the first study to directly link metal exposure with vector competence (i.e., ability to transmit parasites) in any vector-parasite system. Additionally, it also demonstrates unequivocally that mosquitoes can transfer contaminants from aquatic to terrestrial ecosystems. These results have broad implications for public health because they directly linking contaminants and vector-borne disease dynamics, as well as linking mosquitoes and contaminant dynamics.

Synergism and unintended effects of the association between imidacloprid and sodium chloride (NaCl) on the management of Euschistus heros

BACKGROUND

The use of insecticidal solutions containing sodium chloride (NaCl) has been proposed as a more environmentally friendly alternative to managing stink bug infestations of Neotropical soybean fields. The potential sublethal and undesirable effects of this practice have, however, been overlooked, especially with novel insecticides. Here, we have evaluated experimentally whether the addition of NaCl (0.5% w/v) to imidacloprid-containing solutions could alter insecticide toxicity and modify the reproductive responses of the Neotropical brown stink bug Euschistus heros.

RESULTS

Adding NaCl to imidacloprid solutions significantly increased imidacloprid toxicity against E. heros. The exposure to E. heros to sublethal concentrations of imidacloprid affected the insect's mating abilities in a concentration-dependent manner. The addition of NaCl to solutions containing imidacloprid at concentrations as low as 0.126 μg a.i. cm^-2 (i.e. the equivalent to 3% of field rate recommendation) also impacted the sexual behavior of E. heros, reducing mating duration. NaCl-exposed stink bugs, however, exhibited higher fecundity and fertility rates than those insects that were unexposed to NaCl or those that were exposed to sublethal levels of imidacloprid only.

CONCLUSIONS

The addition of low amounts of NaCl resulted in a higher toxicity of imidacloprid. This practice, however, can also lead to undesirable effects as increasing reproductive output of E. heros that can potentially compromise the management of these insect pests.

Wolbachia's Deleterious Impact on Aedes aegypti Egg Development: The Potential Role of Nutritional Parasitism

Simple Summary

Mosquito-borne viral diseases such as dengue, Zika and chikungunya cause a significant global health burden and are currently increasing in outbreak frequency and geographical reach. Wolbachia pipientis, an endosymbiotic bacterium, offers a solution to this. When Wolbachia is introduced into the main mosquito vector of these viruses, Aedes aegypti, it alters the mosquito’s reproductive biology, as well as reducing the ability of the mosquitoes to transmit viruses. These traits can be leveraged to reduce virus transmission within a community by mass releasing Wolbachia-infected mosquitoes. However, Wolbachia has some negative effects on Aedes aegypti fitness, particularly egg longevity, and the reason behind this remains ambiguous. Insect fitness is very important for the success for Wolbachia-biocontrol strategies as they rely on the released insects being competitive with the wild mosquito population. This review summarises the fitness effects of Wolbachia on Aedes aegypti and investigates the possible contribution of Wolbachia as a nutritional parasite in lowering host fitness. It proposes the next stages of research that can be conducted to address nutritional parasitism to aid in the expansion of Wolbachia-based disease management programs worldwide.

Abstract

The artificial introduction of the endosymbiotic bacterium, Wolbachia pipientis, into Aedes (Ae.) aegypti mosquitoes reduces the ability of mosquitoes to transmit human pathogenic viruses and is now being developed as a biocontrol tool. Successful introgression of Wolbachia-carrying Ae. aegypti into native mosquito populations at field sites in Australia, Indonesia and Malaysia has been associated with reduced disease prevalence in the treated community. In separate field programs, Wolbachia is also being used as a mosquito population suppression tool, where the release of male only Wolbachia-infected Ae. aegypti prevents the native mosquito population from producing viable eggs, subsequently suppressing the wild population. While these technologies show great promise, they require mass rearing of mosquitoes for implementation on a scale that has not previously been done. In addition, Wolbachia induces some negative fitness effects on Ae. aegypti. While these fitness effects differ depending on the Wolbachia strain present, one of the most consistent and significant impacts is the shortened longevity and viability of eggs. This review examines the body of evidence behind Wolbachia’s negative effect on eggs, assesses nutritional parasitism as a key cause and considers how these impacts could be overcome to achieve efficient large-scale rearing of these mosquitoes.

Immunometabolism in Arthropod Vectors: Redefining Interspecies Relationships

Metabolism influences biochemical networks, and arthropod vectors are endowed with an immune system that affects microbial acquisition, persistence, and transmission to humans and other animals. Here, we aim to persuade the scientific community to expand their interests in immunometabolism beyond mammalian hosts and towards arthropod vectors. Immunometabolism investigates the interplay of metabolism and immunology. We provide a conceptual framework for investigators from diverse disciplines and indicate that relationships between microbes, mammalian hosts and their hematophagous arthropods may result in cost-effective (mutualism) or energetically expensive (parasitism) interactions. We argue that disparate resource allocations between species may partially explain why some microbes act as pathogens when infecting humans and behave as mutualistic or commensal organisms when colonizing arthropod vectors.

Integrating statistical and mechanistic approaches with biotic and environmental variables improves model predictions of the impact of climate and land-use changes on future mosquito-vector abundance, diversity and distributions in Australia

Changes to Australia's climate and land-use patterns could result in expanded spatial and temporal distributions of endemic mosquito vectors including Aedes and Culex species that transmit medically important arboviruses. Climate and land-use changes greatly influence the suitability of habitats for mosquitoes and their behaviors such as mating, feeding and oviposition. Changes in these behaviors in turn determine future species-specific mosquito diversity, distribution and abundance. In this review, we discuss climate and land-use change factors that influence shifts in mosquito distribution ranges. We also discuss the predictive and epidemiological merits of incorporating these factors into a novel integrated statistical (SSDM) and mechanistic species distribution modelling (MSDM) framework. One potentially significant merit of integrated modelling is an improvement in the future surveillance and control of medically relevant endemic mosquito vectors such as Aedes vigilax and Culex annulirostris, implicated in the transmission of many arboviruses such as Ross River virus and Barmah Forest virus, and exotic mosquito vectors such as Aedes aegypti and Aedes albopictus. We conducted a focused literature search to explore the merits of integrating SSDMs and MSDMs with biotic and environmental variables to better predict the future range of endemic mosquito vectors. We show that an integrated framework utilising both SSDMs and MSDMs can improve future mosquito-vector species distribution projections in Australia. We recommend consideration of climate and environmental change projections in the process of developing land-use plans as this directly impacts mosquito-vector distribution and larvae abundance. We also urge laboratory, field-based researchers and modellers to combine these modelling approaches. Having many different variations of integrated (SDM) modelling frameworks could help to enhance the management of endemic mosquitoes in Australia. Enhanced mosquito management measures could in turn lead to lower arbovirus spread and disease notification rates.

Not Just from Blood: Mosquito Nutrient Acquisition from Nectar Sources

Anthropophilic female mosquitoes are well known for their strong attraction to human hosts, but plant nectar is a common energy source in their diets. When sugar sources are scarce, female mosquitoes of some species can compensate by taking larger and more frequent blood meals. Male mosquitoes are exclusively dependent on plant nectar or alternative sugar sources. Plant preference is likely driven by an innate attraction that may be enhanced by experience, as mosquitoes learn to recognize available sugar rewards. Nectar-seeking involves the integration of at least three sensory systems: olfaction, vision and taste. The prevention of vector-borne illnesses, the determination of the mosquitoes' ecological role, and the design of efficient sugar-baited traps will all benefit from understanding the molecular basis of nectar-seeking.

Aedes aegypti (Diptera: Culicidae) Immune Responses with Different Feeding Regimes Following Infection by the Entomopathogenic Fungus Metarhizium anisopliae

The mosquito Aedes aegypti is the most notorious vector of illness-causing viruses. The use of entomopathogenic fungi as bioinsecticides is a promising alternative for the development of novel mosquito control strategies. We investigate whether differences in immune responses could be responsible for modifications in survival rates of insects following different feeding regimes. Sucrose and blood-fed adult A. aegypti females were sprayed with M. anisopliae 1 × 106 conidia mL-1, and after 48 h, the midgut and fat body were dissected. We used RT-qPCR to monitor the expression of Cactus and REL1 (Toll pathway), IMD, REL2, and Caspar (IMD pathway), STAT and PIAS (JAK-STAT pathway), as well as the expression of antimicrobial peptides (Defensin A, Attacin and Cecropin G). REL1 and REL2 expression in both the midgut and fat body were higher in blood-fed fungus-challenged A. aegypti than in sucrose-fed counterparts. Interestingly, infection of sucrose-fed insects induced Cactus expression in the fat body, a negative regulator of the Toll pathway. The IMD gene was upregulated in the fat body in response to fungal infection after a blood meal. Additionally, we observed the induction of antimicrobial peptides in the blood-fed fungus-challenged insects. This study suggests that blood-fed A. aegypti are less susceptible to fungal infection due to the rapid induction of Toll and IMD immune pathways.

Non-canonical transcriptional regulation of heme oxygenase in Aedes aegypti

Heme oxygenase (HO) is a ubiquitous enzyme responsible for heme breakdown, which yields carbon monoxide (CO), biliverdin (BV) and ferrous ion. Here we show that the Aedes aegypti heme oxygenase gene (AeHO - AAEL008136) is expressed in different developmental stages and tissues. AeHO expression increases after a blood meal in the midgut, and its maximal transcription levels overlaps with the maximal rate of the further modified A. aegypti biglutaminyl-biliverdin (AeBV) pigment production. HO is a classical component of stress response in eukaryotic cells, being activated under oxidative stress or increased heme levels. Indeed, the final product of HO activity in the mosquito midgut, AeBV, exerts a protective antioxidant activity. AeHO, however, does not seem to be under a classical redox-sensitive transcriptional regulation, being unresponsive to heme itself, and even down regulated when insects face a pro-oxidant insult. In contrast, AeHO gene expression responds to nutrient sensing mechanisms, through the target of rapamycin (TOR) pathway. This unusual transcriptional control of AeHO, together with the antioxidant properties of AeBV, suggests that heme degradation by HO, in addition to its important role in protection of Aedes aegypti against heme exposure, also acts as a digestive feature, being an essential adaptation to blood feeding.

Iron and Ferritin Deposition in the Ovarian Tissues of the Yellow Fever Mosquito (Diptera: Culicidae)

Dengue, yellow fever, and Zika are viruses transmitted by yellow fever mosquito, Aedes aegypti [Linnaeus (Diptera: Culicidae)], to thousands of people each year. Mosquitoes transmit these viruses while consuming a blood meal that is required for oogenesis. Iron, an essential nutrient from the blood meal, is required for egg development. Mosquitoes receive a high iron load in the meal; although iron can be toxic, these animals have developed mechanisms for dealing with this load. Our previous research has shown iron from the blood meal is absorbed in the gut and transported by ferritin, the main iron transport and storage protein, to the ovaries. We now report the distribution of iron and ferritin in ovarian tissues before blood feeding and 24 and 72 h post-blood meal. Ovarian iron is observed in specific locations. Timing post-blood feeding influences the location and distribution of the ferritin heavy-chain homolog, light-chain homolog 1, and light-chain homolog 2 in ovaries. Understanding iron deposition in ovarian tissues is important to the potential use of interference in iron metabolism as a vector control strategy for reducing mosquito fecundity, decreasing mosquito populations, and thereby reducing transmission rates of vector-borne diseases.

Mosquito Host-Seeking Regulation: Targets for Behavioral Control

Female Aedes aegypti mosquitoes require protein from blood to develop eggs. They have evolved a strong innate drive to find and bite humans and engorge on their blood. Decades of research have revealed that attraction to hosts is suppressed for days after blood-feeding. During this time, females coordinate complex physiological changes, allowing them to utilize blood protein to develop eggs: clearing excess fluid, digesting protein, and egg maturation. How do mechanosensation, nutrient consumption, and reproductive pathways combine to produce the full expression of host-seeking suppression? Understanding mechanisms of endogenous host-seeking suppression may allow them to be 'weaponized' against mosquitoes through exogenous activation and developed as tools for vector control. Recent work allows unprecedented genetic and pharmacological access to characterize and disrupt this behavioral cycle.

Microorganism-Based Larval Diets Affect Mosquito Development, Size and Nutritional Reserves in the Yellow Fever Mosquito Aedes aegypti (Diptera: Culicidae)

Background

Mosquito larvae feed on organic detritus from the environment, particularly microorganisms comprising bacteria, protozoa, and algae as well as crustaceans, plant debris, and insect exuviae. Little attention has been paid to nutritional studies in Aedes aegypti larvae.

Objectives

We investigated the effects of yeast, bacteria and microalgae diets on larval development, pupation time, adult size, emergence, survivorship, lifespan, and wing morphology.

Materials and Methods

Microorganisms (or Tetramin^® as control) were offered as the only source of food to recently hatched first instar larvae and their development was followed until the adult stage. Protein, carbohydrate, glycogen, and lipid were analyzed in single larvae to correlate energetic reserve accumulation by larva with the developmental rates and nutritional content observed. FITC-labeled microorganisms were offered to fourth instar larvae, and its ingestion was recorded by fluorescence microscopy and quantitation.

Results and Discussion

Immature stages developed in all diets, however, larvae fed with bacteria and microalgae showed a severe delay in development rates, pupation time, adult emergence and low survivorship. Adult males emerged earlier as expected and had longer survival than females. Diets with better nutritional quality resulted in adults with bigger wings. Asaia sp. and Escherichia coli resulted in better nutrition and developmental parameters and seemed to be the best bacterial candidates to future studies using symbiont-based control. The diet quality was measured and presented different protein and carbohydrate amounts. Bacteria had the lowest protein and carbohydrate rates, yeasts had the highest carbohydrate amount and microalgae showed the highest protein content. Larvae fed with microalgae seem not to be able to process and store these diets properly. Larvae were shown to be able to process yeast cells and store their energetic components efficiently.

Conclusion

Together, our results point that Ae. aegypti larvae show high plasticity to feed, being able to develop under different microorganism-based diets. The important role of Ae. aegypti in the spread of infectious diseases requires further biological studies in order to understand the vector physiology and thus to manage the larval natural breeding sites aiming a better mosquito control.

Interacting stressors matter: diet quality and virus infection in honeybee health

Honeybee population declines have been linked to multiple stressors, including reduced diet diversity and increased exposure to understudied viral pathogens. Despite interest in these factors, few experimental studies have explored the interaction between diet diversity and viral infection in honeybees. Here, we used a mixture of laboratory cage and small semi-field nucleus hive experiments to determine how these factors interact. In laboratory experiments, we found that high-quality diets (polyfloral pollen and high-quality single-source pollen) have the potential to reduce mortality in the face of infection with Israeli acute paralysis virus (IAPV). There was a significant interaction between diet and virus infection on mortality, even in the presence of high virus titres, suggesting that good diets can help bees tolerate virus infection. Further, we found that extreme stress in the form of pollen starvation in conjunction with IAPV infection increase exiting behaviour from small experimental hives. Finally, we showed that higher-quality pollen diets have significantly higher iron and calcium content, suggesting micronutrient deficiencies could be an under-explored area of bee nutrition.