Infection of Aedes albopictus with chikungunya virus rectally administered by enema.

Chikungunya virus (CHIKV) is an alphavirus transmitted by Aedes albopictus and Aedes aegypti mosquitoes in tropical areas of Africa, Asia, and the islands of the Indian Ocean. In 2007 and 2009, CHIKV was transmitted outside these tropical areas and caused geographically localized infections in people in Italy and France. To temporally and spatially characterize CHIKV infection of Ae. albopictus midguts, a comparison of viral distribution in mosquitoes infected per os or by enema was conducted. Ae. albopictus infected with CHIKV LR 5' green fluorescent protein (GFP) at a titer 10(6.95) tissue culture infective dose(50) (TCID(50))/mL, were collected and analyzed for virus dissemination by visualizing GFP expression and titration up to 14 days post inoculation (dpi). Additionally, midguts were dissected from the mosquitoes and imaged by fluorescence microscopy for comparison of midgut infection patterns between orally- and enema-infected mosquitoes. When virus was delivered via enema, the anterior midgut appeared more readily infected by 3 dpi, with increased GFP presentation observed in this same location of the midgut at 7 and 14 dpi when compared to orally-infected mosquitoes. This work demonstrates that enema delivery of virus is a viable technique for use of mosquito infection. Enema injection of mosquitoes may be an alternative to intrathoracic inoculation because the enema delivery more closely models natural infection and neither compromises midgut integrity nor involves a wound that can induce immune responses. Furthermore, unlike intrathoracic delivery, the enema does not bypass midgut barriers to infect tissues artificially in the hemocoel of the mosquito.

Switchover to the mated state by spermathecal activation in female Anopheles gambiae mosquitoes.

Both Aedes aegypti and Anopheles gambiae mosquitoes undergo physiological and behavioral changes after the females mate, but unlike Ae. aegypti, the mated state in An. gambiae is not attained through the action of male accessory gland substances. Experiments in which the spermathecae of mated females were manipulated suggest that a spermatheca filled with sperm is responsible for triggering oviposition behavior. An estimated 48% of the previously mated An. gambiae females mated again when the interval between encounters with males was less than 24h. Unlike male Ae. aegypti that can inseminate up to seven females after their testes are removed, An. gambiae do not store sperm in the vas deferens and without testes would be unable to inseminate any females.

Mating affects egg maturation in Anopheles gambiae Giles (Diptera: Culicidae).

The effect of mating on egg development and the size of the female accessory glands during the gonotrophic cycle of Anopheles gambiae was investigated. Although females that received a measured meal of blood were more likely to produce an egg batch when they were mated, the increased reproduction was not the result of male accessory gland substances. Changes in the size of the female accessory gland were not observed after mating nor at any time during the gonotrophic cycle, but there was a more rapid increase in its size following emergence in mated females.

Production of polymorphic sperm by anopheline mosquitoes and their fate within the female genital tract.

The males of two mosquito species within the Anopheles gambiae complex, An. gambiae s.s. and An. quadriannulatus, as well as males of An. darlingi, produced sperm of significantly varying lengths, while a sperm polymorphism was absent in Aedes aegypti and other anophelines not suspected of belonging to species complexes. The polymorphic distribution of these sperm lengths was not significantly different in smaller adult males that were reared on a low larval diet. The reproductive tract of the female was more likely to contain larger sperm, but overall sperm retention varied depending on the size of the female and the volume of the spermatheca she contained. The presence of a sperm polymorphism may be a factor that has promoted speciation, as well as providing an indication that females may mate multiply.

Contributions of insect research toward our understanding of neurosecretion.

The process of neurosecretion is an important and widespread method of biological communication among animals. Although insects and vertebrates appear to be very different, neurosecretory mechanisms and the neuropeptides themselves are often the same. The gradual acceptance of neurosecretion as a biological phenomenon, largely as a result of research done with insects, is discussed.

Mating alters the cuticular hydrocarbons of female Anopheles gambiae sensu stricto and aedes Aegypti (Diptera: Culicidae).

The cuticular hydrocarbons of female Anopheles gambiae Giles sensu stricto and Aedes aegypti (L.) mosquitoes were analyzed before and after they mated. In An. gambiae, the proportions of the two cuticular hydrocarbon components, n-heneicosane and n-tricosane, were significantly reduced as the female aged and after it mated. There were no changes in the hydrocarbon composition of males after they mated. Hydrocarbon extracts from mated and unmated An. gambiae females as well as those from males caused a reduction in the rates of female insemination when they were applied to unmated females. Female Ae. aegypti showed significant changes in the proportions of n-heptadecane, n-pentacosane and n-hexacosane in their cuticles after mating. These data suggest that cuticular hydrocarbons may play some role in chemical communication during mosquito courtship.