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Mar Biol (2007) 151:21592166 DOI 10.1007/s00227-007-0648-6
RESEARCH ARTICLE
Retention of functional chloroplasts in some sacoglossans from the Indo-Pacic and Mediterranean
Jussi Evertsen Ingo Burghardt Geir Johnsen Heike Wagele
Received: 30 May 2006 / Accepted: 16 February 2007 / Published online: 7 March 2007 Springer-Verlag 2007
Abstract Previous studies on kleptoplasty in sacoglossans have used different methodology to investigate how long the sacoglossans are able to keep photosynthetically active (functional) chloroplasts. In this study we have used Pulse Amplitude Modulated Fluorometry to measure the quantum yield of charge separation in photosystem II in dark acclimated cells (FIIe) to detect the status of photo-synthetic activity. Seven species of sacoglossa, Plakobranchus ocellatus, Elysia timida, Elysia sp, Elysia tomentosa, Thuridilla carlsoni, T. lineolata and Elysiella pusilla, were investigated regarding their ability to retain functional chloroplasts (RFC). The results show three different levels of RFCs where P. ocellatus has the longest RFC for more than 11 months, E. timida with a RFC 1/4 than P. ocellatus (almost 3 months) and the rest with RFCs down to 1/22 of P. ocellatus (up to 15 days). Based on these results, and compared to previous studies, eight different levels of retention abilities of non-functional and functional chloroplasts in sacoglossans are proposed. As
far as we know, this is a novel method studying chloroplast functionality in sacoglossans.
Introduction
Sacoglossan mollusks (Opisthobranchia) are specialized herbivores feeding on marine macroalgae and seagrasses (Clark and Busacca 1978; Jensen 1980, 1997; Williams and Walker 1999). Morphological and physiological adaptations enable several members of sacoglossans to ingest intact chloroplasts and keep (incorporate) them photosynthetically active in the digestive cells in the gut for varying time periods, but the chloroplasts are not autonomous in the way that they are not able to divide (Taylor 1968; Trench 1969; Greene 1970; Hinde and Smith 1972, 1974, 1975; Trench 1975; Trench and Olhorst 1976; Clark and Busacca 1978; Hawes 1979; Jensen 1996; Williams and Walker 1999; Rumpho et al. 2000). This ability has also been termed kleptoplasty (Waugh and Clark 1986; Clark et al. 1990).
Based on carbon xation rates in different sacoglossans, Clark et al. (1990), suggested six levels of kleptoplasty. Level 1 represented direct digestion of chloroplasts, level 2 retention of non-functional chloroplasts for less than 2 h, and level 3...