The Combined Effects of Bacterial Symbionts and Aging on Life History Traits in the Pea Aphid, Acyrthosiphon pisum

• Type of Material: Article
• Authors: Alice M. Laughton, Emory University; Maretta H. Fan, Emory University; Nicole Gerardo, Emory University
• Language: English
• Date: 2014-01-15
• Publisher: American Society for Microbiology
• Publication Version: Final Published Version
• Copyright Statement: © 2014, American Society for Microbiology. All Rights Reserved.
• Final Published Version (URL): http://dx.doi.org/10.1128/AEM.02657-13
• Title of Journal or Parent Work: Applied and Environmental Microbiology
• ISSN: 0099-2240
• Volume: 80
• Issue: 2
• Start Page: 470
• End Page: 477
• Grant/Funding Information: This research was funded by National Science Foundation grant IOS-1025853 (N.M.G. and A.M.L.).
• Research Categories: Biology, General; Chemistry, General

Abstract

While many endosymbionts have beneficial effects on hosts under specific ecological conditions, there can also be associated costs. In order to maximize their own fitness, hosts must facilitate symbiont persistence while preventing symbiont exploitation of resources, which may require tight regulation of symbiont populations. As a host ages, the ability to invest in such mechanisms may lessen or be traded off with demands of other life history traits, such as survival and reproduction. Using the pea aphid, Acyrthosiphon pisum, we measured survival, lifetime fecundity, and immune cell counts (hemocytes, a measure of immune capacity) in the presence of facultative secondary symbionts. Additionally, we quantified the densities of the obligate primary bacterial symbiont, Buchnera aphidicola, and secondary symbionts across the host's lifetime. We found life history costs to harboring some secondary symbiont species. Secondary symbiont populations were found to increase with host age, while Buchnera populations exhibited a more complicated pattern. Immune cell counts peaked at the midreproductive stage before declining in the oldest aphids. The combined effects of immunosenescence and symbiont population growth may have important consequences for symbiont transmission and maintenance within a host population.