Papel de las actividades superóxido dismutasa y catalasa en la ...

1. Introduction
Fish aquaculture is an expanding industry worldwide. Marine aquaculture in
southern Europe has focused on species such as gilthead seabream (Sparus aurata, L.)
and sea bass (Dicentrarchus labrax, L.). However, the diversification of the species
farmed is required and Senegalese sole (Solea senegalensis, Kaup) is a species with a
high economic value, which is farmed in Portugal and Spain [1]. Diseases of bacterial
origin constitute the most significant cause of economic losses suffered in the
aquaculture industry [2]. The most frequently isolated pathogen from outbreaks detected
in farmed Senegalese sole is Photobacterium damselae subsp. piscicida, which is
responsible for high mortalities in cultured fish [3]. Antibiotic treatment of bacterial
diseases affecting farmed fish has been applied for many years. However, the
occurrence of antibiotic resistance in pathogenic bacteria is limiting the usefulness of
these substances [4-6] and therefore, several alternative strategies to the use of
antimicrobials have been proposed, including the use of immunostimulants which
represent a promising tool in aquaculture. Indeed, many authors have reported that the
injection of immunostimulants, such as glucans, enhances the function of leucocytes
and protection against pathogens [7-10]. Several authors have observed that P.
damselae subsp. piscicida is highly susceptible to oxidative radicals generated during
the macrophage respiratory burst [11, 12]. However, other authors have reported the
presence of intact cells of this pathogen inside fish cells, suggesting the ability of the
bacterium to survive as an intracellular pathogen [13-17]. For this reason, the
stimulation of the respiratory burst activity of the phagocytes of Senegalese sole could
facilitate a more effective destruction of P. damselae subsp. piscicida.
Marine organisms constitute a potential alternative source of substances for the
prevention and treatment of infectious diseases [18]. In this connection, algae have been
studied as dietary ingredients for fish nutrition [19] and as a source of bioactive
compounds such as pharmaceutical [20, 21] and immunostimulant [22-25] agents.
Several authors [26] have suggested a possible stimulation of the metabolic and
functional action of phagocytic system cells from Balb/c mice after intraperitoneal
administration of polysaccharides isolated from cultures in the stationary phase of red
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