Clash of mosquito wings: Larval interspecific competition among the mosquitoes, Culex pipiens, Aedes albopictus and Aedes aegypti reveals complex population dynamics in shared habitats.

Globalisation, climate change and international trade are the factors contributing to the spread of Aedes albopictus (Diptera: Culicidae) and Ae. aegypti into new areas. In newly invaded habitats, these non-native species can serve as arbovirus disease vectors or increase the risk of disease spill over. These mosquitoes continue to emerge in new areas where they have or will have overlapping ranges with other resident mosquito species. The study investigates how invasive Aedes mosquitoes compete with the native Culex pipiens in Türkiye, which might affect the overall mosquito population dynamics and disease transmission risks. Both Aedes species exhibited contrasting responses to interspecific competition with Cx. pipiens. While Ae. albopictus suffers reduced emergence primarily in larger containers with abundant food, Ae. aegypti surprisingly thrives in mixed cultures under all food conditions. Adult Cx. pipiens emergence drops by half against Ae. albopictus and under specific conditions with Ae. aegypti. Competition influences mosquito size differently across species and life stages. Culex pipiens females grow larger when competing with Ae. aegypti, potentially indicating resource advantage or compensatory strategies. However, Ae. albopictus size shows more nuanced responses, suggesting complex interactions at play. Understanding how invasive and native mosquitoes interact with each other can provide insights into how they adapt and coexist in shared habitats. This knowledge can inform effective control strategies. The study highlights the differential responses of invasive Aedes species and the potential for managing populations based on their competitive interactions with the native Cx. pipiens. It can contribute to improved monitoring and prediction systems for the spread of invasive mosquitoes and the associated disease risks.

Population Genetics of Culex tritaeniorhynchus (Diptera: Culicidae) in Türkiye.

PURPOSE: Mosquitoes are important vectors of pathogens that can affect humans and animals. Culex tritaeniorhynchus is an important vector of arboviruses such as Japanese encephalitis virus, West Nile virus among various human and animal communities. These diseases are of major public health concern and can have huge economic and health burdens in prevalent countries. Although populations of this important mosquito species have been detected in the Mediterranean and Aegean regions of Türkiye; little is known about its population structure. Our study is to examine the population genetics and genetic composition of Cx. tritaeniorhynchus mosquitoes collected from several localities using cytochrome oxidase subunit I (COI) and the NADH dehydrogenase subunit 5 genes (ND5). This is the first extensive study of Cx. tritaeniorhynchus in the mainland Türkiye with sampling spanning many of provinces. METHODS: In this study, DNA extraction, amplification of mitochondrial COI and ND5 genes and population genetic analyses were performed on ten geographic populations of Culex tritaeniorhynchus in the Aegean and Mediterranean region of Türkiye. RESULTS: Between 2019 and 2020, 96 samples were collected from 10 geographic populations in the Aegean and Mediterranean regions; they were molecularly analyzed and 139 sequences (50 sequence for COI and 89 sequence for ND5) were used to determine the population structure and genetic diversity. For ND5 gene region, the samples produced 24 haplotypes derived from 15 variable sites and for COI gene region, 43 haplotypes were derived from 17 variable sites. The haplotype for both gene regions was higher than nucleotide diversity. Haplotype phylogeny revealed two groups present in all populations. AMOVA test results show that the geographical populations were the same for all gene regions. Results suggest that Cx. tritaeniorhynchus is a native population in Türkiye, the species is progressing towards speciation and there is no genetic differentiation between provinces and regions. CONCLUSION: This study provides useful information on the molecular identifcation and genetic diversity of Cx. tritaeniorhynchus; these results are important to improve mosquito control programs.

Larvicidal Activity of Some Aromatic Thiosemicarbazone and Metal Complexes [Ni (II), Cu (II), Co (II)] Against Aedes (Stegomyia) aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1894) (Diptera: Culicidae) Larvae.

Objective: A series of aromatic thiosemicarbazone-oxime [TP1 and TP2] derivatives and their Ni(II), Cu(II), and Co(II) complexes were synthesized, and their larvicidal activity was evaluated against Aedes aegypti and Aedes albopictus larvae. The efficacy of these substances to Aedes albopictus larvae has been demonstrated for the first time. Methods: Laboratory colonized Aedes aegypti and Aedes albopictus larvae were subjected to larvicidal activity tests. Larval mortality rates at 24 and 48 hours were recorded and LC50 values were calculated. The study was carried out at Aydin Adnan Menderes University in 2021. Results: For Aedes aegypti, LC50 of TP1 and its Co(II) complex were 15.41, 9.75, µg/mL whereas for TP2 and its Co(II) complex, LC50 were 21.62, 20.50 µg/mL after 24 and 48 h respectively. For Aedes albopictus, TP1 and its Co(II) complex showed an LC50 of 12.06, 8.75 µg/mL, whereas TP2 and its Co(II) complex showed an LC50 of 32.87, 25.48 µg/mL, for 24, and 48 h respectively. Conclusion: Both TP1 and TP2 compounds and their Co(II) complexes presented high efficacy against the larvae; it can be said that C=S groups in thiosemicarbazone derivatives are effective in showing activity and for this reason, studies should be continued to make these components effective.

Detection of L1014F knockdown resistance mutation in Culex tritaeniorhynchus populations.

Culex tritaeniorhynchus is a major Japanese encephalitis virus vector distributed in Southeast Asia and surrounding countries. The aim of the present study is to investigate insecticide resistance status among 10 Cx. tritaeniorhynchus populations of the Mediterranean region of Turkey. Bioassay results indicated that all of the populations were resistant or at least possibly resistant to 1,1'-(2,2,2-Trichloroethane-1,1-diyl) bis (4-chlorobenzene) (DDT) (4%), [(dimethoxyphosphorothioyl) sulfanyl] butanedioate, Diethyl (malathion) (5%), and 2-[(Propan-2-yl) oxy] phenyl methylcarbamate (propoxur) (0,1%). Whereas, some of the populations were still susceptible to 3-Phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate (permethrin) (0,75%) and (S)-Cyano (3-phenoxy phenyl) methyl (1R,3R)-3-(2,2-dibromoethen-1-yl)-2,2-dimethylcyclopropane-1-carboxylate (deltamethrin) (0,05%). Biochemical analysis results showed altered alpha esterase, beta esterase, para-nitrophenyl acetate (PNPA), and glutathione-s-transferase (GST) levels in some populations while all of the populations had increased oxidase levels except for the Yumurtalik population. Additionally, all of the populations had sensitive acetylcholinesterase (AChE) levels similar to the control group except for the Erzin population. Correlation analysis showed a significant correlation between mortality rates for deltamethrin and alpha esterase, beta esterase, PNPA, and GST levels while mortality rates for permethrin were significantly correlated with GST levels. An allele-specific polymerase chain reaction (AS-PCR) detected high L1014F allele frequency in the populations. Overall results indicate the urgent need for monitoring and mapping of insecticide resistance in Cx. tritaeniorhynchus populations of the study area for effective vector control management.