Abstract
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.
Highlights
The solitary ascidian Ciona robusta, exhibiting an almost transparent body, is characterized by a wide geographical distribution[1]
C. robusta is becoming an endangered resource in some a reas[33], due to global and local environmental changes impacting its survival
Chemical and physical parameters of water were kept within the optimal ranges known for the survival of C. robusta during our experimental trials (Fig. 1)
Summary
The solitary ascidian Ciona robusta, exhibiting an almost transparent body, is characterized by a wide geographical distribution[1]. It is a euryhaline and eurytherm s pecies[2,3] living in areas of high turbidity and in coastal lagoons[4,5,6]. 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 m2 in polluted communities9,10), especially in colder seasons[6]. We tested the efficiency on growth rates and mortality rates of such different particles with average size ranging from yeast cells (3–40 μm) to larger algae contained in the Shellfish diet and Algamac (300–600 μm)
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