Meeting Abstract

P3.18  Wednesday, Jan. 6  An Ultrastructural Comparison of Cells Lining the Digestive Diverticulum of 4 Sacoglossan Species of Differing Kleptoplastic Abilities CURTIS, N.E.*; PIERCE, S.K.; SCHWARTZ, J.A.; MIDDLEBROOKS, M; University of South Florida ncurtis2@mail.usf.edu

Certain species of the sea slug group Sacoglossa incorporate intact, functional chloroplasts from their algal food sources into specialized cells lining the digestive diverticulum. Most slug species are unable to maintain these plastids for more than a week. However, in Elysia clarki, the chloroplasts are photosynthetically functional for many months and there is evidence that at least 1 nuclear encoded, algal gene for a chloroplast protein has been horizontally transferred into the slug genome. E. clarki can feed on species from several ulvophytic genera, including species of the Bryopsidilean genera Penicillus and Bryopsis. Other sacoglossans (E. patina, E. rufescens, and P. kingstoni) share algal food sources with E. clarki, but are unable to maintain the chloroplasts for more than a week, with P. kingstoni apparently being unable to maintain chloroplasts for more than 24 hrs. We have performed extensive ultrastructural analysis on the chloroplast sequestering cells of these animals looking for morphological differences that may account for the variations in chloroplast sequestering and maintenance amongst sacoglossans. Our results indicate that P. kingstoni does not actively sequester chloroplasts, digesting them instead. However, the sequestering mechanisms of E. patina and E. rufescens are similar to E. clarki, and therefore the differences in sequestered chloroplast longevity may be explained by the presence or absence of transferred algal genes.