Importance of prebiotics in aquaculture as immunostimulants. Effects on immune system of Sparus aurata and Dicentrarchus labrax Donatella Carbone, Caterina Faggio * Department of Biological and Environmental Sciences, University of Messina Viale Ferdinando Stagno d'Alcontres, 31 98166, S.Agata, Messina, Italy article info Article history: Received 1 March 2016 Received in revised form 5 April 2016 Accepted 8 April 2016 Available online 10 April 2016 Keywords: Prebiotics Immune system Sparus aurata Dicentrarchus labrax Disease control abstract Infectious diseases in ﬁsh represent a major problem for the aquaculture ﬁeld as they produce extensive damages and loss. Over the last few years, with increased development of the aquaculture industry, different methods have been used to contrast these pathologies. Common interest has led to the use of components (as additives in diets) that could contrast diseases without causing any negative impact on the environment. These components are represented by prebiotics, probiotics, and plant extracts. In this review, the effects of prebiotics are described. Prebiotics are indigestible ﬁbres fermented by gut en- zymes and commensal bacteria, whose beneﬁcial effects are due to the by-products generated from fermentation. The inﬂuence of pre-biotics on the immune system of ﬁsh is called immunosaccharides. Mannanoligosaccharides (MOS), Fructooligosaccharides (FOS) and Inulin act at different levels in the innate immune response. For example, through phagocytosis, lysozyme activity, and the complement system activity, an increase in ﬁsh growth and an amelioration of their health status is brought about. In this review, the use of prebiotics in aquaculture, such as immunostimulants, has been highlighted: particularly in two teleost ﬁsh species, Sparus aurata and Dicentrarchus labrax. The results demonstrate that the road is still long and further studies are required, but the use of prebiotics, individually or coupled together, can open the doors to pioneering a new model of alternative components to antimi- crobial agents. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Fish and ﬁshery products represent a source of proteins and essential micronutrients that are important for human health. Aquaculture (the farming of ﬁsh, shellﬁsh, and aquatic plants) is among one of the fastest-growing sectors in world food production: for the last decade it has supplied one-third of seafood consumed worldwide [1]. However infectious diseases are the major imped- iment to the development of aquaculture and are often the most signiﬁcant cause of economic lost [2]. Infectious diseases are caused by different bacterial and viral pathogens. To control diseases, similar strategies (vaccination and the use of anti-microbial agents) are employed in aquaculture as in other areas of animal farming. Antibiotics have routinely been administered, but as a consequence, there have been negative impacts on the environment and on human health. This includes the emergence of antibiotic-resistant bacterial strains, the accu- mulation of residual in edible tissues, and the depression of im- mune systems [3,4]. For these reasons, the use of antibiotic treatment in aquaculture has resulted in a ban in Europe and stringent regulations on the application of antibiotics in the United States and other countries. This has prompted interest in devel- oping alternative strategies to disease control [5]. The de- velopments in the aquaculture sector in recent decades have increased interest in the study of ﬁsh-growth through the enhancement of the piscine immune system by manipulating diet. Alternative methods of disease prevention have been sought out via immunostimulants, probiotics, prebiotics, and symbiotics, as additives in the diet [6]. The administration of functional dietary supplements has been the alternative approach to the use of chemical products. Different feed additives such as probiotics and prebiotics have been found to be beneﬁcial for improving the im- mune status, feed efﬁciency, and growth performance in ﬁsh [7] and shellﬁsh [8,9]. Indeed, many medicinal plants and their ex- tracts act as immunostimulants. The use of immunostimulants has * Corresponding author. Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Ferdinando Stagno d'Alcon- tres, 31-98166, S.Agata, Messina, Italy. E-mail address: cfaggio@unime.it (C. Faggio). Contents lists available at ScienceDirect Fish & Shellﬁsh Immunology journal homepage: www.elsevier.com/locate/fsi http://dx.doi.org/10.1016/j.fsi.2016.04.011 1050-4648/© 2016 Elsevier Ltd. All rights reserved. Fish & Shellﬁsh Immunology 54 (2016) 172e178