Rui-de Xue and Donald R. Barnard, Mentors
Andrew Kao is dissecting Aedes albopictus mosquitos to count the eggs. He is learning how sublethal levels of a toxin affect behavior and fecundity.
Using a suction tube to capture mosquitos from a cage.
Effect of low doses of toxic baits on host-seeking, blood feeding, and fecundity in Aedes albopictus
Mosquitoes pose problems to humans and animals as a vector for disease transmission. Liquid formulations of toxic baits have been used to kill adult mosquitoes. However, intake doses vary from mosquito to mosquito and do not always result in the death of the mosquito. In such situations, it would be of interest to examine the effects of low doses of toxic baits on host seeking, blood feeding, and fecundity in mosquitoes. The information from this study could be used to understand the potential for controlling mosquitoes using low doses of toxic baits and to reduce pesticide application for mosquito control. The experiment was conducted with adult female Aedes albopictus and divided into two parts. The first examined the host seeking and blood feeding behavior of Aedes albopictus and the second explored whether or not fecundity was affected. Female Ae. albopictus were separated into treatment and control groups where the treatment groups received 0.1% of the toxic baits. To test host seeking, treatment groups and control groups of 100 females each were placed in an olfactometer with a human hand as an attractant. To examine blood-feeding behavior, individual female mosquitoes were placed in clear plastic feeding cages and allowed to feed on a guinea pig. Fecundity effects were compared by blood-feeding both the treatment and control groups, and then they were held in the laboratory condition (25°C and 14L:10D). Seventy-two hours after blood feeding, mosquitoes were dissected and examined for egg abundance and development. Blood-engorged females were allowed to lay eggs and the number of eggs was compared between treatment and control groups. In these experiments it was found that the toxic baits at low dose application did affect host-seeking and blood-feeding behaviors. In the host-seeking test, 26% of the control mosquitoes were attracted to the human hands within 3 min exposure, while only 11% of the treatment group females were attracted. Blood feeding tests showed that only 12% of the control group did not feed in the allotted time, whereas 52% of the treatment group refused to feed. The fecundity tests showed that female mosquitoes in control groups yielded 9.5- 20 times eggs more than in treatment groups. Dissected mosquitoes from the control groups showed IV-V stage of follicular development after 72 hours, while treatment mosquitoes showed II-III stage of development. The experiments showed that the low doses of toxic baits affect host seeking and blood feeding behavior in Aedes albopictus, and reduced fecundity.