The results of the present study indicated that stenogamous laboratory-reared Ae. albopictus can successfully mate with their wild counterparts. Females from the laboratory-raised colony laid eggs in considerable numbers when mated with wild males. Mating between WF and LM yielded large numbers of eggs. The female offspring that resulted from these cross-mating events showed increased fecundity, particularly those derived from the mating of WF × WM and mated with WF.
LF produced more eggs than their wild counterparts when both mated with WM. Laboratory-maintained insect strains are thought to have greater energy stores than wild strains as they are exposed to less severe environmental conditions. In the laboratory environment, the high-nutrient larval conditions result in the production of large-sized individuals. Fecundity has often been correlated with body size in mosquitoes. In general, small females produce fewer eggs and have delayed ovarian development [40, 41], and larger females produce more eggs over a lifetime than small individuals . In this study, body size measurements indicated that females derived from wild pupae (WF) and those in the laboratory (LF) were of similar size, strongly suggesting that female body size may not have played a role in the observed differences in egg production between wild and laboratory strains.
Crosses between WF × LM and WF × WM showed comparable fecundity. In addition, the fecundity of wild pairs was similar to that of primary offspring of LF mated with WM, similar to the observations reported previously . These researchers investigated the fitness and sexual cross-compatibility between wild and laboratory populations of the malaria vector, Anopheles arabiensis that originated from material collected in 1994, and noted that the reproductive fitness of the laboratory strain was not significantly modified with respect to the wild pairs. They attributed the decreased variations apparent in the fitness of the laboratory strain to the reduction in genetic variation generally inherent in laboratory colonies. In addition, Muhenga and colleagues  observed increased insemination rates of wild females by laboratory-acclimated males, and suggested that this increased mating success was a result of a high degree of genetic compatibility between the two strains. It is possible that there was a similar genetic affinity between the laboratory and wild populations of Ae. albopictus used in this study. It is interesting to note that the colony used was far older than that in the study of Muhenga and co-workers —both LF and LM were derived from a < 25-year-old laboratory colony and WF were collected in the field as pupae in early 2012. Mating between the laboratory pairs and LM with WF was highly productive. The hatching success rate of eggs from WF mated with LM was similar to that of eggs from WF mated with WM. In addition, eggs derived from LF × WM and LF × LM crosses had similar hatching success rates; there were no significant differences in egg production between primary female offspring and parents when both were mated with WM. Finally, the adult lifespan of female offspring of WF × WM crosses was similar to that of their counterparts from WF × LM crosses. Taken together, these results suggest that Ae. albopictus has retained both reproductive and physiological fitness while being kept in the laboratory for 25 years.
Similar to Ae. albopictus, many arthropods known to be involved in the transmission of pathogens to humans, domestic animals, and wildlife are maintained in laboratories for research purposes . Containment is necessary to gain information regarding their behavior, life cycle, infectivity, and susceptibility to infection-blocking strategies . Previous research in Ae. albopictus has helped us gain a better understanding of the medical importance of this species. This mosquito is known to transmit at least 22 human arboviruses, including flaviviruses (dengue virus, yellow fever virus, Japanese encephalitis virus, and West Nile virus) and togaviruses (Ross River virus) . Ae. albopictus is also a vector of alphaviruses, such as Chikungunya  and equine fever . No vaccines or preventative drug treatments are currently available for most of these arboviral infections. This mosquito species is also highly invasive [46, 47]. Although it is indigenous to Southeast Asia, Ae. albopictus has traversed the world over the past 30 years  and is listed by the World Conservation Union as one of the world’s most invasive species . Ecological studies have indicated that climate does not significantly constrain the establishment of this mosquito [47, 49], which is capable of overwintering in cold climates [50, 51]. Another specific characteristic of this mosquito species is that it is capable of transovarial transmission of dengue serotypes 1, 2, 3, and 4 to its offspring . Thus, an infected female can transmit the virus to the next generation via its eggs. In addition, male-to-female sexual transfer has also been documented in this mosquito; males experimentally infected with all dengue serotypes transmitted their infection to females through mating . In this study, LFs were more fecund than WF when both mated with WM. Clearly, in nature, increased fecundity will tend to result in higher cumulative offspring rates, and the mosquito populations are more likely to persist in nature with increased egg production. Epidemiologically, if LF is infected with dengue virus, the increased egg production observed when LF or their offspring mate with WF will, therefore, lead to high population densities, but also propagation and maintenance of virus infection.
Pathogen-infected vectors represent an immediate threat, but even uninfected arthropods that escape captivity can establish populations that subsequently transmit pathogens . Despite guidelines for safe containment of colonies to prevent inadvertent escape [14, 15], there have been a few instances where an insect has escaped from a laboratory and resulted in a significant public health issue. One of the most striking examples is Rhodnius prolixus; indigenous to northern South America, this Chagas disease vector was introduced into Central America by escape from a laboratory in El Salvador in 1915 . Work with colonies of Aedes mosquitoes is associated with a high risk of the escape of eggs, which measure only about 1 mm, from the laboratory. In the case of Aedes dengue vectors, it is known that eggs can survive in the environment for several months and then hatch at the onset of rain . Therefore, the World Health Organization has suggested that eggs be taken into consideration in arthropod containment measures .