Honors College Theses

Publication Date

2023

Major

Biology (B.S.B.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Dr. Lisa Brown

Abstract

In holometabolous insects, conditions during the larval stage can affect the adult stage. For instance, in mosquitoes, reduced larval food and high density can make adults more susceptible to infection. Fleas (Siphonaptera), like mosquitoes, go through complete metamorphosis and have adult stages that exclusively feed on the blood of vertebrates, including humans. However, flea larvae have chewing mandibles and rely on nutrients from dried fecal matter containing vertebrate blood proteins. Their limited mobility and unique nutritional needs confine their development to specific areas, likely leading to frequent larval competition in natural conditions. Yet, the influence of larval density on the subsequent adult stage has not been explored. In our study using cat fleas (Ctenocephalides felis), we investigated the impact of larval competition on development to adulthood, adult body size, and adult immunity. We collected eggs to form three groups with different larval population densities (n = 50, 100, and 150), and maintained consistent nutritional conditions between all groups. We tracked development from eggs to pupae and adulthood, measured head and total body length of adults, and exposed eclosed adults to a blood meal with live bacteria (Serratia marcescens) for 24 hours to determine infection loads. Our findings indicate that low larval density negatively impacts the transition from pupa to adults, decreases adult size, and increased adult female susceptibility to infection. Overall, our study provides valuable insights into how larval density shapes the biology of resulting adult fleas.

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