Date of Award

Spring 2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Program/Concentration

Biomedical Sciences

Committee Director

Chris Osgood

Committee Member

Shawn Dash

Committee Member

Alvin Holder

Committee Member

Kneeland Nesius

Committee Member

Hameeda Sultana

Abstract

This dissertation discusses mosquito behavioral activities involving circadian rhythms defined as insect sensitivity to select of chemical volatiles that vary throughout the 24-hour day. Circannual rhythms occur over seasons varying in photoperiod, defined as the seasonal cycle of light and darkness. These cycles can be endogenously controlled by circadian clocks. The impetus for this research was initiated when reading about the neglected temporal dimension in the context of insect chemical ecology, including insect olfaction. It was proposed that sensitivity to odors does not change in general, but specific sensitivities could vary according to time of day. Chemical scents emitted by host or conspecifics could change according to time of day or season. The serious omission of not including the temporal dimension in the correct timing of assays can lead to false or misleading results upon interpretation of data.

The two mosquito species that I studied were male and female Culex restuans and Aedes albopictus. These species were selected because they differ in both circadian rhythms and photoperiod. Aedes albopictus is diurnal and is active primarily in the summer. Culex restuans is crepuscular/nocturnal and is active primarily in the spring and fall. The inclusion of male mosquitoes has been considered an important first step in the study of male mosquito behavioral ecology, as there is a gender imbalance when researching and studying mosquitoes.

The measuring instruments utilized to conduct my entomology experiments were a flexible dual port olfactometer, and laboratory constructed photoperiodic light regimes. The four chemicals used to test olfactory mosquito responses were acetone, carbon dioxide, lactic acid, and octanol. The floral scents tested for Culex restuans included Clethra, Fennel, and Oregano Plants, and Mountain Mint. Aedes albopictus scents tested were Rose absolot, Lavendar Oil, Sweet Orange, and Cilantro and Mountain Mint (flowers and leaves).

The results of these entomology experiments revealed the following information: Although there were differences between species and between female and male mosquito response to select odorants, several female and male mosquitoes of both species did respond positively to specific host odors and floral scents. Neither males nor females of Aedes albopictus demonstrated significant preferences for either the host odors or the floral scents tested. However, Culex restuans females significantly preferred the host odors of carbon dioxide and lactic acid treatments to control filtered air. In contrast, Culex restuans males did not show a positive response to either chemical. Future research into the chemical ecology of male and female mosquitoes will be helpful in investigating these differences.

Comments

Deborah A. Waller -- Dissertation Committee Member

DOI

10.25777/nc09-8g62

ISBN

9798641557434

ORCID

0000-0001-9510-9209

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