Date of Award

5-2020

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Matthew Aardema

Committee Member

Lisa Hazard

Committee Member

Kisrten Monsen

Subject(s)

Culex pipiens, Circadian rhythms

Abstract

Mosquitos within the Culex pipiens species complex are primary vectors of West Nile virus in North America. The most common member of this complex in New Jersey, Cx. pipiens f. pipiens, is adapted to a temperate climate and females enter a diapause state as adults each winter. In contrast, its co-occurring sister taxon, Cx. pipiens f. molestus, is unable to enter the diapause state and both males and females continue feeding and breeding during winter months. Females additionally continue to lay eggs. The molestus form can do so because it is highly adapted to urban environments and is predominantly found in manmade underground locations. Prior studies have shown that the genes associated with circadian rhythms (i.e. ‘clock genes’) also influence the photoperiodic induction of diapause in Cx. pipiens. Here I investigated whether New World Cx. pipiens f. molestus maintains circadian rhythms despite its inability to enter a diapause state. The adult emergence of mosquitos reared in 12:12 light:dark, constant light, and constant dark had circular means in or around early scotophase (dark period). The adult emergence of mosquitos reared in the contrasting cycle of 12:12 dark:light had a circular mean after lights on, which was scotophase in the incubator. These results indicate that circadian rhythms in New World Cx. pipiens f. molestus are entrained by environmental cues during the larval period. Genetic analysis using BLASTn compared the expression of known clock genes in Cx. pipiens f. molestus and the closely related species Cx. quinquefasciatus. All known clock genes were expressed in Cx. pipiens f. molestus and suggest that the lack of diapause in these mosquitos is unlikely to be caused by major inactivating mutations in known clock genes.

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