title: Photosynthate accumulation in solar-powered sea slugs - starving slugs survive due to accumulated starch reserves.
abstract: BACKGROUND
  Solar-powered sea slugs are famed for their ability to survive starvation due to incorporated algal chloroplasts. It is well established that algal-derived carbon can be traced in numerous slug-derived compounds, showing that slugs utilize the photosynthates produced by incorporated plastids. Recently, a new hypothesis suggests that the photosynthates produced are not continuously made available to the slug. Instead, at least some of the plastid's photosynthetic products are stored in the plastid itself and only later become available to the slug. The long-term plastid-retaining slug,Elysia timidaand its sole food source,Acetabularia acetabulumwere examined to determine whether or not starch, a combination of amylose and amylopectin and the main photosynthate produced byA. acetabulum, is produced by the stolen plastids and whether it accumulates within individual kleptoplasts, providing an energy larder, made available to the slug at a later time.
  
  
  RESULTS
  Histological sections ofElysia timidathroughout a starvation period were stained with Lugol's Iodine solution, a well-known stain for starch granules in plants. We present here for the first time, an increase in amylose concentration, within the slug's digestive gland cells during a starvation period, followed by a sharp decrease. Chemically blocking photosynthesis in these tissues resulted in no observable starch, indicating that the starch in untreated animals is a product of photosynthetic activity.
  
  
  CONCLUSIONS
  This suggests that kleptoplasts function as both, a nutritive producer and storage device, holding onto the polysaccharides they produce for a certain time until they are finally available and used by the starving slug to withstand extended starvation periods.
authors.affiliation: Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany.|Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, Bonn, 53121 Germany.
authors.forename: Elise M J
authors.initials: EMJ
authors.lastname: Laetz
authors.affiliation: Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany.
authors.forename: Victoria C
authors.initials: VC
authors.lastname: Moris
authors.affiliation: Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany.
authors.forename: Leif
authors.initials: L
authors.lastname: Moritz
authors.affiliation: Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany.
authors.forename: André N
authors.initials: AN
authors.lastname: Haubrich
authors.affiliation: Zoological Research Museum Alexander Koenig, 162 Adenauerallee, Bonn, 53113 Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Wägele
keywords: Amylose; Elysia; Kleptoplast; Lugol’s Iodine; Sacoglossa; Starch