Circadian clock genes period and cycle regulate photoperiodic diapause in the bean bug Riptortus pedestris males

The photoperiodic response is crucial for many insects to adapt to seasonal changes in temperate regions. It was recently shown that the circadian clock genes period (per) and cycle (cyc) are involved in the photoperiodic regulation of reproductive diapause in the bean bug Riptortus pedestris females. Here, we investigated the involvement of per and cyc both in the circadian rhythm of cuticle deposition and in the photoperiodic diapause of R. pedestris males using RNA interference (RNAi). RNAi of per and cyc disrupted the cuticle deposition rhythm and resulted in distinct cuticle layers. RNAi of per induced development of the male reproductive organs even under diapause-inducing short-day conditions, whereas RNAi of cyc suppressed development of the reproductive organs even under diapause-averting long-day conditions. Thus, the present study suggests that the circadian clock operated by per and cyc governs photoperiodism of males as that of females.     

Pathogenicity Tests on Nine Mosquito Species and Several Non-target Organisms with Strelkovimermis spiculatus (Nemata Mermithidae)

Nine species of mosquitoes and several species of non-target aquatic organisms were tested for susceptibility to the mernaithid nematode, Strelkovimermis spiculatus. All species of Anopheles, Aedes, Culex, and Toxorhynchites exposed to S. spiculatus were susceptible. Of the nine mosquito species tested, C. pipiens quinquefasciatus had the greatest tolerance to initial invasion and the highest percent infection of those that survived. High levels of infection were also achieved with Aedes taeniorhynchus and A. albopictus, but these mosquitoes were significantly less tolerant to parasitism than C. pipiens quinquefasciatus. Strelkovimermis spiculatus did not infect or develop in any of the non-target hosts tested.     

Malaria Vector Surveillance in Ganghwa-do, a Malaria-Endemic Area in the Republic of Korea

We investigated the seasonality of Anopheles mosquitoes, including its species composition, density, parity, and population densities of mosquitoes infected with the parasite in Ganghwa-do (Island), a vivax malaria endemic area in the Republic of Korea. Mosquitoes were collected periodically with a dry-ice-tent trap and a blacklight trap during the mosquito season (April-October) in 2008. Anopheles sinensis (94.9%) was the most abundant species collected, followed by Anopheles belenrae (3.8%), Anopheles pullus (1.2%), and Anopheles lesteri (0.1%). Hibernating Anopheles mosquitoes were also collected from December 2007 to March 2008. An. pullus (72.1%) was the most frequently collected, followed by An. sinensis (18.4%) and An. belenrae (9.5%). The composition of Anopheles species differed between the mosquito season and hibernation seasons. The parous rate fluctuated from 0% to 92.9%, and the highest rate was recorded on 10 September 2008. Sporozoite infections were detected by PCR in the head and thorax of female Anopheles mosquitoes. The annual sporozoite rate of mosquitoes was 0.11% (2 of 1,845 mosquitoes). The 2 mosquitoes that tested positive for sporozoites were An. sinensis. Malarial infections in anopheline mosquitoes from a population pool were also tried irrespective of the mosquito species. Nine of 2,331 pools of Anopheles mosquitoes were positive. From our study, it can be concluded that An. sinensis, which was the predominant vector species and confirmed as sporozoite-infected, plays an important role in malaria transmission in Ganghwa-do.     

Length variation in a specific region of the period gene correlates with differences in pupal diapause incidence in the flesh fly, Sarcophaga bullata

We report differences in the length of a specific region of the circadian clock gene period (per) that correlate with different capacities for pupal diapause in the flesh fly, Sarcophaga bullata. The conspicuous difference is located in a region we refer to as the putative C-terminal photoperiodic (CP) region. The length of the CP region correlates inversely with the incidence of diapause. A deletion of 33 amino acids in this region correlates with a significant increase in the incidence of diapause, from 78.1% to 93.0%, and an insertion of 9 amino acids in the same area correlates with a drop in the diapause incidence to 4.0%. This correlation suggests a possible functional role for this region of per in photoperiodism.     

Induction of apoptosis in densovirus infected Aedes aegypti mosquitoes

The mechanism of death in densovirus infected mosquitoes remains unexplored. This study investigated the cellular consequences of densovirus infection in Aedes aegypti mosquitoes after a second generation challenge with a densovirus isolated from adult Aedes albopictus mosquitoes in Thailand (AThDNV). Specimens were analyzed by TUNEL assay, fluorescent in situ hybridization (FISH) and a calorimic assay to detect activation of caspase 3-like activity. After challenge, moribund mosquitoes showed considerable evidence of TUNEL positive cells. The caspase 3-like activity assay showed that the presence of TUNEL positive cells was associated with increased levels of activated caspase 3-like activity in AThDNV infected mosquitoes.     

Satyrization without evidence of successful insemination from interspecific mating between invasive mosquitoes

Previous research has documented low frequencies of interspecific mating in nature between the invasive vectors Aedes aegypti and Aedes albopictus. It is also known that heterospecific male accessory gland substances transferred during mating sterilize A. aegypti but not A. albopictus females, leading to satyrization, a form of reproductive interference. This paper demonstrates that satyrization of A. aegypti by A. albopictus may occur without evidence of successful insemination. Our results show that A. aegypti females, previously exposed to A. albopictus males, are rendered refractory to subsequent conspecific mating even though their spermathecae contain no heterospecific sperm. Additional experiments demonstrating transfer of labelled semen from A. albopictus males to A. aegypti females and low production of viable eggs of females housed with conspecific males, following exposure to A. albopictus males, confirm higher incidences of satyrization than expected, based on heterospecific insemination rates. We conclude that frequencies of satyrization based on detection of interspecific sperm in spermathecae may underestimate the impact of this form of reproductive interference.     

Inheritance of the photoperiodic response controlling imaginal summer diapause in the cabbage beetle, Colaphellus bowringi

Adults of the cabbage beetle Colaphellus bowringi display a summer diapause in response to the exposure of their larvae to long photoperiods. In the present study, the inheritance of the photoperiodic response controlling summer diapause in C. bowringi by crossing a high diapause strain (D strain) with a laboratory selected nondiapause strain (N strain) was investigated under different photoperiods at 22, 25 and 28 °C. The beetles in both reciprocal crosses and backcrosses showed a clear short-day response for the induction of diapause at all temperatures, similar to that of the D strain, suggesting that photoperiodic response of this beetle is heritable. The diapause incidences in the progeny from all the crosses under LD 15:9 or LD 12:12 at 25 °C suggest that genetic and genetic-environmental interactions are involved in diapause induction. The incidence of diapauses in F₁ progeny was significantly lower than that in the D × D strain but significantly higher than that in the N × N strain, indicating that the diapause capability is inherited in an incomplete dominant manner. The incidence of diapause was greater among the offspring of hybrid females when those females had a D strain mother or grandmother rather than a N strain mother or grandmother, indicating that maternal effects on diapause induction are stronger than paternal effects. The laboratory selected nondiapause strain also showed a short-day photoperiodic response at a low temperature of 22 °C, indicating that the photoperiodic photoreceptor and photoperiodic clock still function in the nondiapause strain.     

Xenomonitoring of Different Filarial Nematodes Using Single and Multiplex PCR in Mosquitoes from Assiut Governorate,Egypt

Wuchereria bancrofti, Dirofilaria immitis, and Dirofilaria repens are filarial nematodes transmitted by mosquitoes belonging to Culex, Aedes, and Anopheles genera. Screening by vector dissection is a tiresome technique. We aimed to screen filarial parasites in their vectors by single and multiplex PCR and evaluate the usefulness of multiplex PCR as a rapid xenomonitoring and simultaneous differentiation tool, in area where 3 filarial parasites are coexisting. Female mosquitoes were collected from 7 localities in Assiut Governorate, were microscopically identified and divided into pools according to their species and collection site. Detection of W. bancrofti, D. immitis, and D. repens using single PCR was reached followed by multiplex PCR. Usefulness of multiplex PCR was evaluated by testing mosquito pools to know which genera and species are used by filarial parasites as a vector. An overall estimated rate of infection (ERI) in mosquitoes was 0.6%; the highest was Culex spp. (0.47%). W. bancrofti, D. immitis, and D. repens could be simultaneously and differentially detected in infected vectors by using multiplex PCR. Out of 100 mosquito pools, 8 were positive for W. bancrofti (ERI of 0.33%) and 3 pools each were positive for D. immitis and D. repens (ERI 0.12%). The technique showed 100% sensitivity and 98% specificity. El-Nikhila, El-Matiaa villages, and Sahel Seleem district in Assiut Governorate, Egypt are still endemic foci for filarial parasites. Multiplex PCR offers a reliable procedure for molecular xenomonitoring of filariasis within their respective vectors in endemic areas. Therefore, it is recommended for evaluation of mosquito infection after lymphatic filariasis eradication programs.