Graduation Year


Document Type




Degree Granting Department

Biology (Integrative Biology)

Major Professor

Susan S. Bell


chlorophyll synthesis, chloroplast, herbivory, photosynthesis, plant-animal interactions, symbiosis


The sacoglossan sea slug Elysia clarki is able to photosynthesize for three to four months using chloroplasts sequestered from its algal food sources. Furthermore, the slug is able to store multiple chloroplasts from different algal species within the same cell. This research, consisting of several related studies, explores the role that provision of organic nutrients via photosynthesis plays in the biology of the slug. The first chapter demonstrates that, under conditions of starvation, photosynthetic activity in E. clarki remains fully functional for one month after which it then declines. During the first month of starvation the slug exhibits similar feeding behavior as slugs provided a continuous supply of food, suggesting that photosynthesis delays the onset of starvation-induced behavioral changes. The second chapter explores E. clarki's spatial relationships with algae known to be food sources in the field. In areas with high slug density, edible algal populations were very low. DNA barcoding was employed to demonstrate that the algae found near slugs were poor predictors of which foods were actually consumed by slugs. Generally, there was a mismatch between algae available in the field and slug diets. The third chapter explores how E. clarki is able to maintain photosynthesis. After labeling with a C14 ALA incubation process, then chlorophyll was extracted from slugs and purified using HPLC. Results indicate that recently collected E. clarki are able to synthesize chlorophyll, whereas slugs starved for 3 months were not. Photosynthesis plays a very important role for E. clarki and its relationships with food algae.