Yellow-y Functions in Egg Melanization and Chorion Morphology of the Asian Tiger Mosquito, Aedes albopictus

The Asian tiger mosquito, Aedes albopictus, is one of the most serious public health pests, which can transmit various vector-borne diseases. Eggs from this mosquito species become dark black shortly after oviposition and exhibit high desiccation resistance. Some of the Yellow proteins that act as dopachrome conversion enzymes (DCEs) are involved in the tyrosine-mediated tanning (pigmentation and sclerotization) metabolic pathway that significantly accelerates melanization reactions in insects. In this research, we analyzed the function of one of the yellow genes, yellow-y (AalY-y), in eggshell/chorion melanization of Ae. albopictus eggs. Developmental and tissue-specific expression measured by real-time PCR showed that AalY-y transcripts were detected at all stages of development analyzed, with significantly higher levels in the ovaries from blood-fed adult females. Injection of double-stranded RNA for AalY-y (dsAalY-y) had no significant effect on fecundity. However, unlike dsEGFP-treated control eggs that become black by 2–3 h after oviposition (HAO), dsAalY-y eggs were yellow-brown at 2 HAO, and reddish-brown even at 48 HAO. dsEGFP eggs exhibited resistance to desiccation at 48 HAO, whereas approximately 50% of the dsAalY-y eggs collapsed when they were moved to a low humidity condition. In addition, TEM analysis revealed an abnormal morphology and ultrastructure of the outer-endochorion in the dsAalY-y eggs. These results support the hypothesis that AalY-y is involved in the tyrosine-induced melanin biosynthetic pathway, plays an important role in black melanization of the chorion and functions in conferring proper morphology of the outer-endochorion, a structure that is presumably required for egg desiccation resistance in Ae. albopictus.

First record of tiger mosquito, Aedes albopictus (Diptera: Culicidae), in La Rioja: Public Health implications

En 2016 se estableció un sistema anual de vigilancia entomológica para la detección de Aedes albopictus en la comunidad autónoma de La Rioja. En el verano de 2020, se detectó por primera vez la presencia de huevos en una zona urbana, lo que constituye el primer registro de esta especie en la región. La identificación de este mosquito invasor supone un cambio en el riesgo de aparición de casos de arbovirosis en La Rioja. La vigilancia entomológica es crucial para el diseño de estrategias de control que, junto con la vigilancia epidemiológica, puedan evitar la aparición de brotes autóctonos de arbovirosis. En este trabajo se detalla el proceso de la primera detección de mosquito tigre en La Rioja, así como las intervenciones llevadas a cabo y las perspectivas de futuro. In 2016, an annual entomological surveillance program for the detection of Aedes albopictus in the autonomous community of La Rioja was established. In the summer of 2020, the presence of eggs was detected for the first time in an urban area, which constitutes the first record of this species in the region. The identification of this invasive mosquito implies a change in the risk of occurrence of arbovirus cases in La Rioja. Entomological surveillance is crucial for the design of control strategies that, together with epidemiological surveillance, can prevent the appearance of autochthonous arbovirus outbreaks. This work is a detailed description of the first detection of tiger mosquito in La Rioja, as well as the completed interventions, and the perspectives for the future.

The effects of genetic drift and genomic selection on differentiation and local adaptation of the introduced populations of Aedes albopictus in southern Russia

Background Asian tiger mosquito Aedes albopictus is an arbovirus vector that has spread from its native habitation areal in Southeast Asia throughout North and South Americas, Europe, and Africa. Ae. albopictus was first detected in the Southern Federal District of the Russian Federation in the subtropical town of Sochi in 2011. In subsequent years, this species has been described in the continental areas with more severe climate and lower winter temperatures. Methods Genomic analysis of pooled Ae. albopictus samples collected in the mosquito populations in the coastal and continental regions of the Krasnodar Krai was conducted to look for the genetic changes associated with the spread and potential cold adaptation in Ae. albopictus. Results The results of the phylogenetic analysis based on mitochondrial genomes corresponded well with the hypothesis that Ae. albopictus haplotype A1a2a1 was introduced into the region from a single source. Population analysis revealed the role of dispersal and genetic drift in the local adaptation of the Asian tiger mosquito. The absence of shared haplotypes between the samples and high fixation indices suggest that gene flow between samples was heavily restricted. Mitochondrial and genomic differentiation together with different distances between dispersal routes, natural and anthropogenic barriers and local effective population size reduction could lead to difficulties in local climatic adaptations due to reduced selection effectiveness. We have found genomic regions with selective sweep patterns which can be considered as having been affected by recent selection events. The genes located in these regions participate in neural protection, lipid conservation, and cuticle formation during diapause. These processes were shown to be important for cold adaptation in the previous transcriptomic and proteomic studies. However, the population history and relatively low coverage obtained in the present article could have negatively affect sweep detection.

Comparative Efficacy of Commercial Liquid and Mat-Type Electric Vaporizer Insecticides Against Asian Tiger Mosquito (Diptera: Culicidae)

Mat and liquid-type electric insecticide vaporizers continuously emit insecticides into the surrounding air. Because both the target insects, mostly mosquitoes, and humans are exposed to those insecticides, it is crucial to understand and monitor their deposition and spatial distribution in treated areas. In the current study, we examined the evaporation of insecticides from seven commercial liquid and mat vaporizers and measured their knock-down and insecticidal activity against the adult females of the Asian tiger mosquito, Aedes albopictus (Skuse). Electric vaporizers from three manufactures had differences in their heaters and active ingredients. Most had continued evaporation during hourly and daily monitoring; however, some liquid vaporizers failed to continue emission to their designated end periods. Overall, mosquitoes located at the upper position in a Peet-Grady chamber and in a field-simulation room exhibited faster knock-down activity than did mosquitoes in other areas, indicating that the insecticides accumulated on the ceiling area. Although most of mat and liquid vaporizers had <60 min of average KT90 values when tested in the Peet-Grady chamber (1.8 × 1.8 × 1.8 m), they failed to have any knock-down in 2 h of observation in the field-simulation room (6.8 × 3.4 × 2.7 m) but showed 72. 8 ± 11.7% and 56. 7 ± 7.3% knock-down in the mat and liquid vaporizers, respectively, in 3 h of operation. Further study will be required to examine whether this relatively limited efficacy can be compensated by other physiological and behavioral effects, including disruption in host-seeking or blood-sucking activities.

Phylogeography and Proline amino acid usage of Asian tiger mosquito Aedes albopictus (Skuse 1894) populations along landscape gradients in Indonesia

Asian tiger mosquito Aedes albopictus (Skuse 1894) is one of mosquito-borne vector that globally distributed including Southeast Asia. Despite its wide distributions, information on phylogeography and its determinant factors influencing A. albopictus genetic diversity and speciation is still lacking, mainly in SE Asia country. Considering this, the phylogeography of A. albopictus along with its genetic attributes in Indonesia has been assessed. The results identify that there are 2 distinct clades of A. albopictus phylogeography. First clade was related to the human-mediated dissemination. Relative Synonymous Codon Usage (RSCU) shows the TTG, CTG, GTG, ACG, GCG, and GGG codons were seldom represented. While GGA, CGA, and followed by TAT, CAT, CCT, TCT, AAC, and TTC codons were common. From a total of 60 codons, 40% codon has RSCU > 1and 21.6 % has RSCU < 1. The differences between west and east part populations can be observed in proline amino acid signaled by CCT and CCC codons. In this amino acid, east A. albopictus has higher CCC than CCT codons. Since proline is functioned to provide energy for flight, then the differences of this proline related codon among A. albopictus populations were related to the landscape variations in west and east parts of Indonesia with east parts have more rugged landscape and this condition is quite demanding for aerial animal distribution since it requires more flight energy.