Food Has No Significant Effect on Color of Elysia crispata, the Solar Powered Lettuce Sea Slug, in a Short Term Study

Undergraduate #216
Discipline: Ecology Environmental and Earth Sciences
Subcategory: Ecology

Zola Roper - University of the Virgin Islands

Elysia crispata is a common herbivorous benthic marine invertebrate known as the lettuce sea slug studied because it has the unusual ability to sequester chloroplast from algal cells and utilize them for energy and coloration. These sequestered chloroplast are taken up by the digestive diverticula. This slug is a sacoglossan species that feeds on green macroalgae by scraping through their cell walls and ingesting the internal cytoplasm. I hypothesized that there would be different changes in coloration of the slug when fed different colored species of green algae, Bryopsis pennata and Caulerpa racemosa, or when it is starved. Thirty (30) slugs ranging between 2 cm to 5.5 cm were collected by snorkel in Brewers Bay, St. Thomas in May 2015. Ten (10) slugs were chosen for each treatment to include the green algae (Bryopsis pennata, Caulerpa racemosa) or starvation. The experiment was ran for 24 days (June 16, 2015 to July 9, 2015). Slugs were photographed before and after the experiment using a digital camera and then images were imported into Image J to obtain RGB (Red Green Blue) values. Additional initial and final weights of the slugs was also taken in grams. The slugs in all three treatments lost weight, but starvation slugs lost the most weight although this was not significant (Kruskal Wallis, P> 0.05). All slugs in each treatment changed Green values. The Green values became lighter in all three treatments but the starvation treatment had the greatest difference although not significant (ANOVA P> 0.05). These results suggest that coloration may not come from the food or that the experiment was too short for changes in coloration to occur.

Funder Acknowledgement(s): This research was supported in part by the National Science Foundation’s Virgin Islands Experimental Program to Stimulate Competitive Research (VIEPSCoR award #1355437) and the Center for Marine and Environmental Studies at the University of the Virgin Islands.

Faculty Advisor: Teresa Turner,