Effects of Body Size and Nutritional Regimen on Survival in Adult Aedes albopictus (Diptera: Culicidae)

Abstract

The effects of adult body size and nutritional regimen on the mean lethal time (LT) to death for the 50th (LT 50) and 90th centiles (LT 90) of large and small male and female Aedes albopictus (Skuse) were determined in the laboratory. The estimated LT 50 and the LT 90 for large/small females were signiÞcantly shorter for test populations receiving water (5.1/3.8 d) or water blood (6.7/5.0 d) than for those receiving sucrose (44.4/31.7 d) or sucrose blood (41.4/29.2 d). The estimated LT 50 and LT 90 for large/small males receiving water (respectively: 3.2/2.5 d and 4.8/3.8 d) were signiÞcantly shorter than for those receiving sucrose (respectively: 18.8/15.9 d and 34.9/32.6 d). The availability of sucrose to adult mosquitoes extended the maximum life span of large and small male and female Ae. albopictus by 6Ð8 when compared with the availability of water or water blood. Results indicate that sugar availability is more important than blood as a nutritional parameter for survival and longevity of Ae. albopictus in the laboratory. KEY WORDS mosquito, blood, carbohydrate, longevity Differences in body size in adult mosquitoes can be important from an epidemiological standpoint. Large Aedes albopictus (Skuse) females have higher human host attack rates and obtain multiple blood meals (from multiple hosts) more frequently than small females (Xue et al. 1995). Body size may also affect mosquito survival and longevity under natural conditions (Nasci 1986). Sugar and blood provide sustenance for adult mosquitoes , and the latter factor enables vitellogenesis (Clements 1992, Foster 1995, Attardo et al. 2005). But the role of nutrient sources relative to mosquito survival cannot be generalized for all species. In Aedes aegypti L., Nayar and Sauerman (1975) found that ingested blood in the absence of sugar availability lengthened survival time. Similarly, Edman et al. (1992) showed that blood-fed Ae. aegypti survived well in domestic settings in Thailand and rarely fed on sugar. In Ae. albopictus, sugar availability equates to improved adult survival in the laboratory (Gao et al. 1984, Hawley 1988, Yap et al. 2003), but data concerning the combined effects of body size and carbohydrate/ blood availability on mosquito survival are lacking. Evaluating these parameters in Þeld populations of mosquitoes is problematic, given the range of possibilities for nutrient availability and rates of uptake by mosquito larvae and the resulting variation in adult body size, age, and vigor. Their evaluation in the laboratory , however, is relatively simple: adult body size can be managed by regulating the density and/or feeding regimen of the larvae, whereas blood and/or carbohydrate sustenance can be offered to adults in holding cages (or withheld) at will. In this study, we determined the relationship between body size, nutritional regimen, and survival in male and female Ae. albopictus in the laboratory. Our objective was to characterize the role of the two former factors as regulators of mosquito survival and longevity. The results are expected to be useful in the culture and management of Ae. albopictus colonies used in biological assays in the laboratory, and may provide a framework for the development of Þeld-testable hypotheses in studies of the effects of nutritional regimen and/or body size on survivorship in adult Ae. albopictus populations in nature. Materials and Methods Mosquito Rearing. We used Ae. albopictus colonized from wild females collected in Gainesville, FL, in 1992. Rearing of larvae and maintenance of stock colony adults was at 27C and 65% RH in a L14:D10 photoperiod. Adults were provided 10% sucrose solution (in water), and females were blood fed on restrained chicken as required for colony maintenance. Large and small adult mosquitoes were obtained by placing 250 and 500 Þrst instars, respectively, in 1 liter of water in a 30-cm L 10-cm W 5-cm H enamel tray, and feeding the larvae according to the regimen 1 Corresponding author: Anastasia Mosquito Control District,