the sea squirt Ciona robusta is a model organism characterized by a transparent body, exhibiting peculiar physiologic and evolutionary characters. in vitro fertilization and breeding of sea squirts is possible, in order to preserve consistent genetic pools. However, some aspects of its biology, as the feeding efficiency according to diet quantity and quality, are still scarcely known. Here we test the effects of three experimental diets on survival and growth, to detect physiological and molecular responses to various types of alimentary suspended particles and the effects of feed concentrations. We also aimed at determining rearing conditions able to limit handling operations, save artificial seawater and control water pollution. Molecular analyses of growth-related genes were performed to detect stressful effects due to feed quality and quantity. A strong effect of doses was highlighted, but water pollution may represent a major concern. A compound diet containing both live algae and non-live particles of a correct size is indispensable to assure development, low stress and high survival rates. Overall, our findings suggest protocols for an easier rearing of Ciona robusta in the laboratory, increasing the potentialities of these organisms as models for research. The solitary ascidian Ciona robusta, exhibiting an almost transparent body, is characterized by a wide geographical distribution 1. It is a euryhaline and eurytherm species 2,3 living in areas of high turbidity and in coastal lagoons 4-6. Several descriptions of C. robusta are available from various locations around the world, along with studies on its taxonomy and the main synonymies 7. This organism may be a dominant member of benthic communities along European coasts 8 , reaching high densities (as high as 2,000 individuals per m 2 in polluted communities 9,10), especially in colder seasons 6. Its wide environmental adaptability permits to live in polluted harbours, as well as in dense seagrass (Posidonia oceanica) meadows 11. It is sensitive to various types of pollution, especially in warmer seasons 12 , when its population naturally decreases 13 but information about the factors influencing winter blooms is still incomplete 5,14. However, the alternation of demographic explosions and consistent numerical reductions is typical of other species of solitary ascidians 15,16 , representing an aspect of their life cycle, still poorly known 17 , that is considered age and density-independent 18-20. Its semi-transparent body not only permits the observation of the internal anatomy, but also to follow the embryo development (after dechorionation, i.e., removal of the follicular cells covering its eggs). The body colour at the distal end of siphons is the main external character distinguishing sister species within its species complex 21. It is a hermaphroditic broadcast spawner, but cannot self-fertilize 22. C. robusta is mostly self-sterile and it has been used for studies on the mechanism of self-incompatibility 23. Its genome has been fully sequenced an...