Date of Award

Spring 2010

Document Type

Restricted Thesis

Terms of Use

© 2010 Julia B. Berthet. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

Elizabeth Ann Vallen


During growth and recovery from bleaching cnidarian hosts must acquire new symbiotic dinoflagellates so as to meet metabolic demands for photosynthetically fixed carbon. In order to better understand the dynamics of cell division and symbiont propagation within new tissues, I characterized the distribution of cells in S-phase, detected in vivo through the incorporation of the nucleotide analog 5-ethynyl-2'-deoxyuridine (EdU). Indices were examined in the ectoderm and gastroderm of Aiptasia pallida in three different symbiotic states: Aposymbiotic, repopulating, and fully symbiotic. Upon exposure to symbionts, levels of proliferation increase dramatically and Aiptasia pallida appear to modulate the distribution of proliferating cells, transitioning from an even distribution of ectodermal growth to a decreasing gradient of proliferation along the tentacle. Aiptasia undergoing repopulation therefore display patterns of cell proliferation, which closely resemble the fully symbiotic state, despite wide disparities in the density of endogenous symbionts, suggesting that symbiont exposure initiates new patterns of cell cycling independently of nutrient availability. Gastrodermal proliferation alternatively exhibits declining proximal-distal gradients of proliferation in aposymbiotic and symbiotic states. During repopulation anemones exhibits a uniform distribution of cells in S-phase, indicating a role for host proliferation in symbiont distribution.