The bio-larvicide Bacillus thuringiensis var. israelensis is effective against Aedes koreicus, either dissolved in water or delivered through eco-compatible chitosan-based hydrogels.

Mosquito control, which is not always easily accomplished, is further complicated by the spread of invasive species. This is the case of Aedes koreicus, a mosquito native to East Asia, whose presence has been recorded in several European countries, including Italy. This mosquito found suitable ecological conditions in central Europe in general, and in northern Italy in particular, as shown by the ongoing expansion of its distribution. While basic knowledge on feeding habits of Ae. koreicus have already been acquired, information on its vectorial competence is scarce. Therefore, active monitoring on the presence of this mosquito, and the pre-planning of future control actions, are of paramount importance. Currently, there are no specific guidelines for controlling this mosquito, both in its native regions and in invaded countries. Here we present the first study on the efficacy of a bioinsecticide based on Bacillus thuringiensis on Ae. koreicus larvae, with a comparison with results obtained on the tiger mosquito Aedes albopictus. Our results proved that this bioinsecticide is effective on Ae. koreicus, both dissolved in water and incorporated into MosChito raft, a hydrogel-based matrix that has recently been developed for the delivery of insecticides to other mosquito species and suitable for safe and eco-compatible applications.

Isolation of a Novel Pythium Species, P. thermoculicivorax, and Trichoderma sp. from Natural Enzootic Mosquito Larval Infections.

Only a handful of microbial mosquito larval pathogens have been described to date. Sampling several natural enzootic infections of mosquito larvae in southwestern Florida indicated the presence of microbial pathogens capable of extensive larval mortality. A microscopic analysis of one sample site revealed extensive apparent growth of a Pythium-like microbe on mosquito larvae, with the highest degree of infection observed in the siphon and head regions. Structures consistent with sporangia were seen on infected insects after lactophenol blue staining, and higher-resolution scanning electron microscopy (SEM) micrographs showed sporangia and encysted zoospores targeting the head and siphon regions. The isolate was single-colony purified, and molecular identification targeting the ITS and COX1 loci coupled to phylogenetic reconstruction indicated that the isolate belonged to the Pythium genus but was distinct from its closest characterized species, P. inflatum. Morphological features were characterized, with the isolate showing rapid growth on all mycological media tested and relatively high thermotolerance, capable of robust growth at 37 °C; hence, it was designated P. thermoculicivorax. Sampling from a second series of natural infections of mosquito larvae resulted in the molecular identification of three Trichoderma isolates, one with high similarity to T. strigosum and the other two clustering closely with T. asperellum. These data highlight the occurrence of natural enzootic infections of mosquito larvae, potentially as a resource for the identification of new mosquito pathogens.

Voltage-gated ion channels are expressed in the Malpighian tubules and anal papillae of the yellow fever mosquito (Aedes aegypti), and may regulate ion transport during salt and water imbalance.

Vectors of infectious disease include several species of Aedes mosquitoes. The life cycle of Aedes aegypti, the yellow fever mosquito, consists of a terrestrial adult and an aquatic larval life stage. Developing in coastal waters can expose larvae to fluctuating salinity, causing salt and water imbalance, which is addressed by two prime osmoregulatory organs - the Malpighian tubules (MTs) and anal papillae (AP). Voltage-gated ion channels (VGICs) have recently been implicated in the regulation of ion transport in the osmoregulatory epithelia of insects. In the current study, we: (i) generated MT transcriptomes of freshwater-acclimated and brackish water-exposed larvae of Ae. aegypti, (ii) detected expression of several voltage-gated Ca2+, K+, Na+ and non-ion-selective ion channels in the MTs and AP using transcriptomics, PCR and gel electrophoresis, (iii) demonstrated that mRNA abundance of many altered significantly following brackish water exposure, and (iv) immunolocalized CaV1, NALCN, TRP/Painless and KCNH8 in the MTs and AP of larvae using custom-made antibodies. We found CaV1 to be expressed in the apical membrane of MTs of both larvae and adults, and its inhibition to alter membrane potentials of this osmoregulatory epithelium. Our data demonstrate that multiple VGICs are expressed in osmoregulatory epithelia of Ae. aegypti and may play an important role in the autonomous regulation of ion transport.

Random Mutational Analysis Targeting Residue K155 within the Transmembrane ß-Hairpin of the Mosquitocidal Mpp46Ab Toxin.

Mpp46Ab is a mosquito-larvicidal pore-forming toxin derived from Bacillus thuringiensis TK-E6. Pore formation is believed to be a central mode of Mpp46Ab action, and the cation selectivity of the channel pores, in particular, is closely related to its mosquito-larvicidal activity. In the present study, we constructed a mutant library in which residue K155 within the transmembrane ß-hairpin was randomly replaced with other amino acid residues. Upon mutagenesis and following primary screening using Culex pipiens mosquito larvae, we obtained 15 mutants in addition to the wild-type toxin. Bioassays using purified proteins revealed that two mutants, K155E and K155I, exhibited toxicity significantly higher than that of the wild-type toxin. Although increased cation selectivity was previously reported for K155E channel pores, we demonstrated in the present study that the cation selectivity of K155I channel pores was also significantly increased. Considering the characteristics of the amino acids, the charge of residue 155 may not directly affect the cation selectivity of Mpp46Ab channel pores. Replacement of K155 with glutamic acid or isoleucine may induce a similar conformational change in the region associated with the ion selectivity of the Mpp46Ab channel pores. Mutagenesis targeting the transmembrane ß-hairpin may be an effective strategy for enhancing the ion permeability of the channel pores and the resulting mosquito-larvicidal activity of Mpp46Ab.

Laboratory scale evaluation of the feasibility of locally found bladderworts as biological agents to control dengue vector, Aedes aegypti in Sri Lanka.

BACKGROUND: The carnivorous genus Utricularia also includes aquatic species that have the potential to trap a wide range of prey, leading its death due to anoxia. However, the effectiveness of such an approach with carnivorous plants for vector control has not been evaluated in Sri Lanka. METHODS: Early instar (i & ii) and late instar (iii & iv) larvae of Aedes aegypti were exposed to locally found bladderwort (U. aurea Lour and Utricularia sp.). The experimental design was set with 10 larvae (both early and late instars separately) in 250 mL of water with bladderworts containing approximately 100 bladders in plant segments of both species, separately. Each treatment and control were repeated 50 times. The survival status of larvae was recorded daily until death or adult emergence. The larvae found whole or partially inside the bladders were attributed to direct predation. The Cox-regression model and Mantel-Cox log rank test were carried out to assess the survival probabilities of larvae in the presence of two bladderworts separately. RESULTS: The highest predation was observed when using early instar larvae in both U. aurea (97.8%) and Utricularia sp. (83.8%). The mortality caused due to predation by U. aurea was observed to be significantly higher according to the Mantel-Cox log-rank test (HR = 60.71, CI; 5.69-999.25, P = 0.004). The mortality rates of late instar stages of Ae. aegypti were observed to be lower in both U. aurea (82.6%) and Utricularia sp. (74.8%). Overall, the highest predation efficacy was detected from U. aurea (HR = 45.02; CI: 5.96-850.51, P = 0.017) even in late instar stages. The results suggested the cumulative predation in both plants on Ae. aegypti larvae was > 72%. CONCLUSIONS: Utricularia aurea is a competent predator of Ae. aegypti larvae. Further, it is recommended to evaluate the feasibility of this plant to be used in the field as a control intervention in integrated vector management programmes.

Predators as biocontrol agents of mosquito larvae in small and large habitats in Chiang Mai, Thailand.

Controlling mosquito-borne disease is a major global challenge due to the rise of insecticide-resistant mosquitoes. In response, we conducted a study in Chiang Mai Province, Thailand, which is one of the largest and the most popular cities for tourists in Southeast Asia, to explore the potential of local species as biological control agents for mosquito larvae. Mosquito larvae and aquatic predators were sampled from large and small habitats, while relevant physico-chemical parameters were measured. The study identified 560 predators and 1,572 mosquitoes, with most mosquito species belonging to the genus Culex. Additionally, the study identified 16 predator taxa, including four fish taxa and 12 taxa of predatory aquatic insects belonging to four orders: Coleoptera, Hemiptera, Odonata, and Diptera. The study found that several locally occurring predator species, namely Poecillia, Laccophilus, Lutzia, Toxorhynchites splendens, Agrionoptera, and Pseudarion, shared habitats with mosquitoes, indicating their potential as effective biological control agents for mosquito control. Conductivity, dissolved oxygen, and pH were the important physico-chemical parameters that affect both predators and mosquito larvae. Consequently, promoting native predators and reducing mosquito larvae through habitat management would be a sustainable and ecologically friendly approach in large habitats where it is not possible to remove mosquito oviposition sites. In smaller habitats, releasing local aquatic predators and removing oviposition sites may be a suitable strategy.

Effects of larval exposure to sublethal doses of ivermectin on adult fitness and susceptibility to ivermectin in Anopheles gambiae s.s.

BACKGROUND: The effects of ivermectin (endectocide) on mosquito survival make it a potential new malaria vector control tool. The drug can be administered to mosquito disease vectors through blood hosts that include humans and livestock. Its increased use may cause contamination of larval habitats, either directly through livestock excreta or indirectly through leaching or run-off from contaminated soil, albeit in sublethal doses. However, the effects of such exposure on immature stages and the subsequent adults that emerge are poorly understood. This study was undertaken to evaluate the impact of ivermectin exposure on Anopheles gambiae s.s. larvae and its effects on fitness and susceptibility to ivermectin in the emerging adults. METHODS: Laboratory-reared An. gambiae s.s. (Kilifi strain) larvae were exposed to five different ivermectin concentrations; 0, 0.00001, 0.0001, 0.001, and 0.01 ppm, and larval survival was monitored to determine the appropriate sub-lethal dose. Concentrations with survival > 50% (0.00001 and 0.0001 ppm) were selected and used as the sub-lethal doses. The fecundity, fertility, and susceptibility to ivermectin of adults emerging after larval exposure to the sub-lethal doses were examined. RESULTS: Overall, exposure of An. gambiae s.s. aquatic stages to ivermectin caused a dose-dependent reduction in larval survival irrespective of the stage at which the larvae were exposed. Exposure to ivermectin in the larval stage did not have an effect on either the number of eggs laid or the hatch rate. However, exposure of first/second-instar larvae to 0.0001 ppm and third/fourth-instar larvae to 0.001 ppm of ivermectin reduced the time taken to oviposition. Additionally, exposure to ivermectin in the larval stage did not affect susceptibility of the emerging adults to the drug. CONCLUSIONS: This study shows that contamination of larval habitats with ivermectin affects An. gambiae s.s. larval survival and could potentially have an impact on public health. However, there are no carry-over effects on the fecundity, fertility, and susceptibility of the emerging adults to ivermectin. In addition, this study shows that environmental exposure to ivermectin in the larval habitats is unlikely to compromise the efficacy of ivermectin in the emerging adults.

Breeding site selection and co-existing patterns of tropical mosquitoes.

We investigated the physicochemical properties and the biotic interactions of breeding sites of tropical mosquito species. Field sampling was done in 12 study areas in Sri Lanka covering areas with secondary natural forests and human settlements. A total of 226 breeding sites were investigated to determine the biotic interactions and physiochemical properties of breeding water (pH, Conductivity, Dissolved Oxygen, Total Dissolved Solids and Temperature). A total of 80.5% of breeding sites from both habitats were positive for mosquito larvae of seven genera and 24 species. Orthopodomyia flavithorax (297) and Aedes albopictus (295) were dominated in tree holes of Alstonia macrophylla, Vateria copallifera and Artocarpus nobilis. Diversity indices showed that the diversity of mosquitoes is high in wet zone habitats of Sri Lanka compared to dry and intermediate zone habitats. Aedes albopictus coexisted with 11 different mosquito species while it avoided larvae of Culex fuscanus, Cx. uniformis and Tripteroides affinis. Strong positive associations were reported between Ae. albopictus and Ar. subalbatus while larvae of Or. flavithorax mosquitoes were not co-occurred with the larvae of Ae. vittatus, Ae. aegypti, Cx. sitiens, Ar. subalbatus, Anopheles spp and Tr. affinis. The findings identified the breeding adaptability and tolerance to a wide range of physiochemical properties of tropical mosquito communities.

Biotoxicity comparison of Bacillus thuringiensis to control vector borne diseases against mosquito fauna.

The current study was designed to evaluate the biotoxicity of screened echo-friendly Bacillus thuringiensis strains from different areas of Pakistan. Out of 50 samples, 36% Bt. isolates were quarantined from soil containing cattle waste after morphological, biochemical, and molecular characterization. The toxicity bioassays with Bt. spores and protein diet proved that 11 Bt. isolates were utmost noxious to 3rd instar larvae of mosquitoes Aedes aegypti, Anopheles stephensi, and Culex pipiens. The entopathogenic activity of first 4 Bt. toxins against A. aegypti was highly lethal as compared to the other dipteran larvae. The toxicity (LC50) of spore diet of Bt. strains GCU-DAB-NF4 (442.730 ± 0.38 µg/ml), NF6 (460.845 ± 0.29 µg/ml), NF3 (470.129 ± 0.28 µg/ml), and NF7 (493.637 ± 0.70 µg/ml) was quite high against A. aegypti as compared to the C. pipiens after 24 h of incubation. The highest toxicity of total cell protein was shown by GCU-DAB-NF4 (LC50 = 84.10 ± 50 µg/ml), NF6 (95.122 ± 0.40 µg/ml), NF3 (100.715 ± 06 µg/ml), and NF5 (103.40 ± 07 µg/ml) against A. aegypti after 24 h. So, these strains a have great potential to be used as biological control especially against A. aegypti as compared to the C. pipiens.

Infection of the malaria vector Anopheles coluzzii with the entomopathogenic bacteria Chromobacterium anophelis sp. nov. IRSSSOUMB001 reduces larval survival and adult reproductive potential.

BACKGROUND: Vector control tools are urgently needed to control malaria transmission in Africa. A native strain of Chromobacterium sp. from Burkina Faso was recently isolated and preliminarily named Chromobacterium anophelis sp. nov. IRSSSOUMB001. In bioassays, this bacterium showed a promising virulence against adult mosquitoes and reduces their blood feeding propensity and fecundity. The current study assessed the entomopathogenic effects of C. anophelis IRSSSOUMB001 on larval stages of mosquitoes, as well as its impacts on infected mosquitoes reproductive capacity and trans-generational effects. METHODS: Virulence on larvae and interference with insemination were assayed by co-incubation with C. anophelis IRSSSOUMB001 at a range of 104 to 108 cfu/ml. Trans-generational effects were determined by measuring body size differences of progeny from infected vs. uninfected parent mosquitoes using wing size as a proxy. RESULTS: Chromobacterium anophelis IRSSSOUMB001 killed larvae of the pyrethroid-resistant Anopheles coluzzii with LT80 of ~ 1.75 ± 0.14 days at 108 cfu/ml in larval breeding trays. Reproductive success was reduced as a measure of insemination rate from 95 ± 1.99% to 21 ± 3.76% for the infected females. There was a difference in wing sizes between control and infected mosquito offsprings from 2.55 ± 0.17 mm to 2.1 ± 0.21 mm in infected females, and from 2.43 ± 0.13 mm to 1.99 ± 0.15 mm in infected males. CONCLUSIONS: This study showed that C. anophelis IRSSSOUMB001 was highly virulent against larvae of insecticide-resistant Anopheles coluzzii, and reduced both mosquito reproduction capacity and offspring fitness. Additional laboratory, field, safety and social acceptance studies are needed to draw firm conclusions about the practical utility of this bacterial strain for malaria vector control.

Comparative efficacy of natural aquatic predators for biological control of mosquito larvae: A neglected tool for vector control.

Mosquitoes are a dominant fraction of dipteran fauna, occupying a variety of niches. The most common method deployed for their control is the use of insecticides. Throughout their life cycle they are exposed to a wide range of predators in different habitats, thus biological control of mosquitoes by using aquatic predators has been suggested. Therefore, the present study was carried out to explore the type of natural predators coexisting with the mosquito larvae in still water bodies and to determine their efficacy as predators for mosquito larvae. A coexistence of different predators with mosquito larvae was observed in 27 standing water bodies of Chandigarh, India. The predation efficiency of tadpoles of frog was comparable to Gambusia fish, as 97% of the mosquito larvae of all instars of the medically important mosquito genera Anopheles, Aedes, Culex and Armigeres were preyed. The toad tadpoles were found to be least effective and their predation rate was found to be negligible. Further studies on larval source management by frog tadpoles in combination with insecticides or stand-alone would be worthwhile.

Manure and mosquitoes: life history traits of two malaria vector species enhanced by larval exposure to cow dung, whilst chicken dung has a strong negative effect.

BACKGROUND: Malaria vectors have a strong ecological association with rice agroecosystems, which can provide abundant aquatic habitats for larval development. Climate-adapted rice cultivation practices, such as the System of Rice Intensification (SRI), are gaining popularity in malaria-endemic countries seeking to expand rice production; however, the potential impact of these practices on vector populations has not been well characterised. In particular, SRI encourages the use of organic fertilisers (OFs), such as animal manures, as low-cost and environmentally friendly alternatives to industrially produced inorganic fertilisers. We therefore set out to understand the effects of two common manure-based OFs on the life history traits of two major African malaria vectors, Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.). METHODS: Larvae of An. arabiensis and An. gambiae s.s. were reared from first instar to emergence in water containing either cow or chicken dung at one of four concentrations (0.25, 0.5, 0.75, and 1.0 g/100 ml), or in a clean water control. Their life history traits were recorded, including survival, development rate, adult production, and adult wing length. RESULTS: Exposure to cow dung significantly increased the development rate of An. gambiae s.s. independent of concentration, but did not affect the overall survival and adult production of either species. Chicken dung, however, significantly reduced survival and adult production in both species, with a greater effect as concentration increased. Interestingly, An. arabiensis exhibited a relative tolerance to the lowest chicken dung concentration, in that survival was unaffected and adult production was not reduced to the same extent as in An. gambiae s.s. The effects of chicken dung on development rate were less clear in both species owing to high larval mortality overall, though there was some indication that it may reduce development rate. Adult wing lengths in males and females increased with higher concentrations of both cow and chicken dung. CONCLUSIONS: Our findings suggest that manure-based OFs significantly alter the life history traits of An. gambiae s.s. and An. arabiensis. In both species, exposure to cow dung may improve fitness, whereas exposure to chicken dung may reduce it. These findings have implications for understanding vector population dynamics in rice agroecosystems and may inform the use of OFs in SRI, and rice agriculture more widely, to avoid their adverse effects in enhancing vector fitness.

Expression of a mosquito larvicidal gene in chloroplast and nuclear compartments of Chlamydomonas reinhardtii.

As a part of the search for environment-friendly biocontrol of mosquito-borne diseases, mosquito larvicidal potential of Bacillus thuringiensis subsp. jegathesan (Btj) Cry toxins is explored for toxins with increased toxicity. Safe delivery of the Cry toxins to mosquito larvae in aquatic habitats is a major concern. This is because in water bodies Bacillus thuringiensis (Bt) protein formulations degrade by sunlight, can sink down and get adsorbed by the silt. So, because of its short persistence the toxin requires repeated applications at the given site. Therefore, an upcoming approach is incorporating the Bt toxins in Chlamydomonas reinhardtii (C. reinhardtii) because it is a food of mosquito larvae in water and its molecular toolkit is well investigated for foreign gene expression. The present work aimed to compare the feasibility of C. reinhardtii chloroplast and nuclear compartments for stable expression of Cry11Ba toxin as this is the most toxic Btj protein to date, lethal to different mosquito species. With chloroplast expression of cry11Ba gene we were able to generate marker-free C. reinhardtii strain stably expressing Cry11Ba protein and demonstrating mortality against Aedes aegypti larvae. Moreover, for nuclear expression linking the cry11Ba gene to zeocin via foot and mouth disease virus (FMDV) 2A peptide resulted in the selection of transformants with increased cry11Ba mRNA expression levels by semi-quantitative reverse transcriptase PCR. Obtained results lay a foundation for the C. reinhardtii chloroplast expression system to be used for genetic engineering with Bt toxins which possess enhanced toxicity.

Docking studies and thiourea-mediated reduced graphene oxide nanosheets' larvicidal efficacy against Culexquinquefasciatus.

The larvicidalproperty of graphene oxide (GO) and thiourea-reduced graphene oxide (T-rGO)was assessed against Culexquinquefasciatuslarvae. A simple water-soluble material synthesis method was used. The transformation of graphene into graphene oxide was accomplished in a single step. Under mild conditions, grapheneoxidewasdissolved in water to form a solution. Structure, optical, and microstructural features of the synthesized samples wereevaluatedusing a variety of analytical tools to compare the samples. Both GO and RGO, as well as GO, showed strong larvicidal potential when used against the third instar larvae of the Culexquinquefasciatus mosquito, with LC50and LC90values of 1.71 and 5.17 ppm and 1.89 and 5.00 ppm, respectively. As a result, our study showed that all of the GO and T-rGO under investigation create larvicidal compounds that could be employed to support efforts to control mosquito populations. It also offers an alternative method for producing GO and rGO on a big scale, which may be used in the future for a variety of biomedical applications.The binding efficacy of the active compounds against AChE1 was studied using Auto dock and the results were observed to be highly promising.

Purification, characterization and toxicity assessment of PirAB toxins from Photorhabdus akhurstii subsp. akhurstii K-1.

Photorhabdus insect related proteins A & B (PirA, PirB) from Photorhabdus and Xenorhabdus bacteria exhibit both oral and injectable toxicity against lepidopteran and dipteran insect pest. The pirA, pirAt (encoding 6 N-terminal truncated PirA), pirB genes, pirA-pirB (with ERIC sequences), pirA-pirB-mERIC (modified pirA-pirB with mutated ERIC sequences) and polycistronic-pirAB were cloned and expressed in Escherichia coli. However, PirA protein was expressed in insoluble form and therefore the pirA gene was modified to produce PirAt. Moreover, pirA-pirB-mERIC, polycistronic-pirAB and co-transformed pirA/pirB genes were not expressed in the studied prokaryotic expression systems. None of the single purified proteins or mixtures of the individually expressed and purified proteins were toxic to mosquito larvae of Aedes aegypti and Culex quinquefasciatus. However, PirA-PirB protein mixtures purified from pirA-pirB operon plasmid were toxic to A. aegypti and C. quinquefasciatus larvae with LC50 values of 991 and 614 ng/ml, respectively. The presence of ERIC sequences between the two orfs of the pirA-pirB operon could help to obtain the proteins in biologically active form. Further, results confirm that PirA-PirB proteins of P. akhurstii subsp. akhurstii K-1 are binary insecticidal toxins and ERIC sequences could play an important role in expression of Pir proteins. Reports of biophysical characterization of individually purified PirAt, PirB and expressed PirA-PirB toxin mixture could provide the structural insight into these proteins.

Effect of ecological factors and breeding habitat types on Culicine larvae occurrence and abundance in residential areas Southern Thailand.

Mosquitoes are a vector of human disease transmitting malaria, and many arboviruses such as dengue virus and Zika virus. This study determined mosquito larval occurrence and abundance in residential areas around Suratthani Rajabhat University as influenced by ecological factors and breeding container diversity. Mosquito larvae were collected using a standard dipping method from 95 locations during April through September 2019 and environmental factors such as physicochemical parameters of water in the breeding containers were measured. During the survey, a total of 194 houses were inspected, of which 58 were found to be infested with mosquito larvae, with a house index of 29.90, a container index of 25.55, and a Breteau index of 48.99. A total of 5,123 mosquito larvae were reported from seven breeding habitat types namely, plastics, cement, mud pots, glass, foam, discarded tires and natural materials. Among the collected larvae, Aedes albopictus (56.45%) was most prevalent, while Culex sp. (22.33%) and Aedes aegypti were less prevalent (21.21%). The most common mosquito larvae breeding habitats were plastics (44.22%) followed by discarded tires (18.14%). The spearman correlation analysis showed that the number of mosquito larvae were significantly positively correlated with the depths and width of containers (p<0.05). These findings are helpful in understanding the ecological factors and breeding habitat types that influence mosquito species and their abundance, and also in determining ways to control mosquito borne diseases.

Pesticides drive differential leaf litter decomposition and mosquito colonisation dynamics in lentic conditions.

Global contamination of freshwater ecosystems by chemical compounds, such as pesticides, may exert high pressure on biologically-driven organic matter decomposition. These pollutants may also impair the quality of organic substrates for colonising invertebrates and reduce primary productivity by decreasing the abundance of phytoplankton. In southern Africa, increasing pesticide usage associated with macadamia plantations, in particular, presents a growing risk to freshwater ecosystems. Here, we examined macadamia (Macadamia integrifolia) leaf litter decomposition following exposure to three pesticides (i.e., Karate Zeon 10 CS (lambda-cyhalothrin), Mulan 20 AS (acetamiprid), Pyrinex 250 CS (chlorpyrifos)) used commonly in macadamia plantations, via an ex-situ microcosm approach. We examined mosquito colonisation of these microcosms as semi-aquatic macroinvertebrates which form a significant component of aquatic communities within standing waters. Macadamia leaf litter tended to decompose faster when exposed to Karate and Pyrinex pesticide treatments. Additionally, chlorophyll-a, conductivity, total dissolved solids, and pH differed among pesticide treatments and controls, with pesticides (Karate Zeon and Mulan) tending to reduce chlorophyll-a concentrations. Overall, pesticide treatments promoted mosquito (i.e., Culex spp.) and pupal abundances. In terms of dominant aquatic mosquito group abundances (i.e., Anopheles spp., Culex spp.), the effect of pesticides differed significantly among pesticide types, with Pyrinex and Mulan treatments having higher mosquito abundances in comparison to Karate Zeon and pesticide-free treatments. These findings collectively demonstrate that common pesticides used in the macadamia plantation may exert pressure on adjacent freshwater communities by shaping leaf-litter decomposition, semi-aquatic macroinvertebrate colonisation dynamics, and chlorophyll-a.

Female mosquito-a potential vector for transporting plastic residues to humans.

With the prodigious use of plastics in the industrial sector and daily life, plastic has become one of the fastest-growing sources of pollution in the aquatic environment. Therefore, ingestion of micro/nanoplastics (MP/NPs) by aquatic organisms is inevitable. But the knowledge on the definite effect, ontogenetic transfer, and translocation of NPs remains incipient. Thus, this study examines the abundance of MPs in mosquito larvae collected from the sewage pit. Additionally, this study demonstrates the MPs-mediated biochemical alterations and effects on development of mosquito, and then ontogenetic transfer and translocation of NPs in Aedes aegypti. Totally 1241 MPs belonging to polyethylene, polycarbonate, polypropylene, polystyrene, polyvinyl chloride and nylon with sizes ranging from 0.5 µm to 80 µm in diameter were isolated from the mosquito larvae. Indeed all the four stages of mosquito larvae feed on NPs and subsequently transfer them to non-feeding pupa and then to flying adult mosquitoes, further to the offspring. However, the NPs exposure and accumulation did not affect the survival of mosquitoes, but altered the biochemical constituents, thereby delaying the development of mosquitoes. Notably the female mosquitoes that emerged from the NPs treatment group showed increased blood-feeding activity and increased starvation resistance capacity. The puzzling accumulation of NPs/residues in different organs, especially in the salivary gland signifies that female mosquitoes could potentially inject polymer residues into humans and animals. At the outset, these observations emphasize that the mosquitoes act as a vector of NPs in the aqueous environment and transport them to terrestrial animals.

Two novel bioassays useful for the quick assessment of chemical effects on the behavior of mosquito larvae (Culicidae) and adult earthworms (Lumbricidae).

The behavior, i.e., observable response of an organism can serve as a useful indicator of environmental quality. In the absence of death and other sublethal effects, behavioral changes can represent early warning signs of toxic effects. In the present contribution, we present two novel bioassays useful for the quick assessment of chemical effects on the behavior of mosquito larvae (Culicidae) and adult earthworms (Lumbricidae). These bioassays could have applications in ecological risk assessment and laboratory based ecotoxicological testing. The novel assays are:•A bioassay for the assessment of chemical toxicity on the swimming, breathing and resting behavior of Culicidae larvae.•A bioassay for the assessment of chemical toxicity on the escape behavior of Lumbricidae in water.•These bioassays were carried out using the systemic insecticide imidacloprid and documented the relatively rapid onset of the neurotoxic effects of imidacloprid to experimental organisms.

Behavioural changes and flight response of a mosquito (Culicidae) and an earthworm (Lumbricidae), respectively, after exposure to imidacloprid.

A major point of concern in ecotoxicology is the effects of pesticides on nontarget organisms. This can impact the ecological role played by certain beneficial species in nature. Regarding neonicotinoid insecticides such as imidacloprid (IMI), several measures, including limited trade, restrictive use, and ban have been implemented in Europe and the USA but not globally. The goal of our study was to evaluate the potential risk of this still widely used agrochemical on the behaviour of mosquito larvae (Culicidae) and the escape behaviour of earthworms (Lumbricidae). Changes in breathing, swimming and resting were recorded in mosquitoes postexposure to 0, 1 and 2 mg IMI/L for 10 min. Earthworms were topically exposed in water for 2 minutes to 0, 5, 10 and 20 mg IMI/L. The escape behaviour (initial escape distance and speed) of the earthworms were recorded. In culicids, resting particularly was significantly increased by the exposure to imidacloprid (p < 0.05). In earthworms, the initial escape distance was statistically longer (p < 0.05) when fleeing from the 5 mg IMI/L solution than the solutions with the two highest concentrations. The worms exposed to the 5 mg IMI/L reacted faster than those exposed to the higher concentrations, which explained the long distance covered in the same amount of time. These results point to the relatively quick onset of the neurotoxic effects of imidacloprid, crippling earthworms and altering the buoyancy of mosquito larvae. The ecological consequences of these findings on the completion of life cycles and the survival of these species in nature are yet to be established.