Final Report Summary - PHOTOSYMBIOXIS (Physiological and Behavioural Photoprotective Processes against Oxidative Stress in Marine Photosynthetic Symbioses) Aim of the project:Marine sacoglossa sea slugs, mainly of the family Plakobranchidea, have developed a unique functional nutritional mode in which they gain the capacity for phototrophic-mediated carbon acquisition using “stolen” chloroplasts (kleptoplasts). Rather than hosting algae endosymbionts, as found in nudibranchs, sacoglossa slugs feed on macroalgae and sequester plastids into tubule cells of their digestive diverticula, a mechanism often named kleptoplasty. These kleptoplasts can sustain photosynthesis for months, although some functional components display short lifespan. It has been hypothesized that algal nuclear genes were transferred to the animal host, supporting photosynthesis in the long-term; however, contradicting reports say this may not be the case. We speculate that retention of functional kleptoplasts inside animal cells may result from a combination of several physical and molecular mechanisms. The main research objective of this project was to study the physiological and behavioural photoprotective processes preventing the occurrence of oxidative stress in kleptoplasts inside the Sacoglossa sea slug Elysia viridis, thus increasing the longevity of photosynthetic activity in these algae organelles inside the animal. Results:The fellow Sónia Cruz, together with the scientist in charge of the project (Prof. João Serôdio), applied their strong background in algae photobiology (i.e. algae metabolism in response to light) to bring insights into the regulation mechanisms that may contribute for maintenance of photosynthetic activity in kleptoplasts inside the animal cells. In the framework of the FP7-People-2012-CIG project 322349, four papers were published in peer-review international journals and Sónia Cruz presented the results of the project at two conferences and one workshop during the course of this project.International collaborations:During the two years course of the project, the funding scheme FP7-MC-CIG allowed establishing international collaborations with the following researchers:- Prof. Mary Rumpho at University of Connecticut, USA. The fellow spent two weeks at University of Connecticut in August 2013 from which work a manuscript is now published);- Prof. Heike Wägele at the Centre for Molecular Biodiversity Research (ZMB) in Bonn, Germany. A Postdoc fellow (Gregor Christa), former PhD student of Prof. Heike Wägele joined our team in October 2014 (DAAD program, joint proposal with Prof. William F. Martin (University of Dusseldorf, Germany) to further advance the work on the thematic of the PhotoSymbiOxiS project.- Prof. Michael Kühl, University of Copenhagen, Denmark. At the end of the Marie Curie CIG project, the fellow started a six months stay at this researcher laboratory aiming at further developing her skills in the use of micro- and nano-sensors and imaging of chlorophyll fluorescence techniques to continue her research in photobiology of animal-algae associations. Career perspectives of the fellow:This grant had a strong impact in the fellow’s career. The scientific advances and established collaborations granted her a researcher contract (5 years) and €50,000 funding for an exploratory project based on previous findings achieved with the CIG project. The research contract was awarded by the Portuguese foundation for Science and Technology (FCT; Fundação para a Ciência e a Tecnologia). With this contract, the fellow achieved a starting level independent position at the host institution (University of Aveiro, Portugal). In addition, the fellow has submitted a larger proposal to continue developing her work in investigating marine photosynthetic associations. The professional re-integration of the fellow was successful and shows promising long-term career perspectives.