5.2 Monday, Jan. 4 Chloroplast retention and satiation in the photosynthetic sea slug Elysia clarki MIDDLEBROOKS, Michael L.*; BELL, Susan S.; PIERCE, Sidney K.; Univ. of S. Florida; Univ. of S. Florida; Univ. of S. Florida firstname.lastname@example.org
Several species of Sacoglossan sea slugs can photosynthesize using sequestered algal chloroplasts. The duration that the chloroplasts retain function varies among slug species. One of the longer lasting examples of kleptoplasty is Elysia clarki, which can maintain chloroplasts for up to 12 weeks without feeding. While chloroplasts are present inside E. clarki’s digestive cells for that duration, the rate at which they decline has not been demonstrated. Nor has the relationship between satiation and feeding behavior of the slugs been examined. Therefore, the progression of chloroplast loss and the effect on feeding behavior in E. clarki over several months was tested using chlorophyll concentration as a proxy for chloroplasts. Slugs were starved for 4, 8, or 12 weeks and compared to a control group that had continuous access to food. Feeding behavior was determined as whether or not slugs would exhibit feeding behavior within five min after exposure to algae. Once feeding behavior was determined, chlorophyll was measured (μg chl/g dry wt). Slugs starved for 4, 8, and 12 weeks exhibited similar feeding behavior, but unstarved control slugs were less likely to feed, most likely due to satiation. Moreover, in slugs starved for 4 or 8 weeks or fed continuously there was no significant difference in chlorophyll concentration. However, the chlorophyll concentration of slugs starved for 12 weeks was statistically lower than slugs from other treatments. This suggests that chloroplast numbers remain constant in E. clarki for 12 weeks post feeding at which point the slugs must feed again. Over a 12 week period slugs will feed when food is available, but they are able to obtain energy from photosynthesis if food is absent. This is the first time that feeding behavior has been examined in regards to chloroplast retention in a photosynthetic animal.