Cruz S LeKieffre C Cartaxana P Hubas C Thiney N Jakobsen S Escrig S Jesus B Kühl M Calado R Meibom A 2020 Some sacoglossan sea slugs incorporate intracellular functional algal chloroplasts, a process termed kleptoplasty. "Stolen" chloroplasts (kleptoplasts) can remain photosynthetically active up to several months, contributing to animal nutrition. Whether this contribution occurs by means of translocation of photosynthesis-derived metabolites from functional kleptoplasts to the animal host or by simple digestion of such organelles remains controversial. Imaging of 13C and 15N assimilation over a 12-h incubation period of Elysia viridis sea slugs showed a light-dependent incorporation of carbon and nitrogen, observed first in digestive tubules and followed by a rapid accumulation into chloroplast-free organs. Furthermore, this work revealed the presence of 13C-labeled long-chain fatty acids (FA) typical of marine invertebrates, such as arachidonic (20:4n-6) and adrenic (22:4n-6) acids. The time frame and level of 13C- and 15N-labeling in chloroplast-free organs indicate that photosynthesis-derived primary metabolites were made available to the host through functional kleptoplasts. The presence of specific 13C-labeled long-chain FA, absent from E. viridis algal food, indicates animal based-elongation using kleptoplast-derived FA precursors. Finally, carbon and nitrogen were incorporated in organs and tissues involved in reproductive functions (albumin gland and gonadal follicles), implying a putative role of kleptoplast photosynthesis in the reproductive fitness of the animal host. application/pdf https://sonar.ch/global/documents/99760 eng info:eu-repo/semantics/altIdentifier/doi/10.1038/s41598-020-66909-7 info:eu-repo/semantics/altIdentifier/pmid/32601288 info:eu-repo/semantics/openAccess Scientific reports. - 2020 Multidisciplinary Functional kleptoplasts intermediate incorporation of carbon and nitrogen in cells of the Sacoglossa sea slug Elysia viridis. http://purl.org/coar/resource_type/c_6501