Nutritional modulation of innate immune parameters in the epidermal mucus of Senegalese sole (Solea senegalensis)=Influência da dieta nos parâmetros da resposta imunitária inata do muco de linguado (Solea senegalensis)

Dissertação mest., Biologia Marinha, Universidade do Algarve, 2008

Fish are in constant interaction with their habitat and potential pathogens. Fish epidermis acts as the first line of defense, since mucus secreted by mucous cells contains innate immune parameters, such as enzymes and antimicrobial proteins. Knowledge about the mechanisms of immune defense at the skin and mucus level in fish is still scarce. This study was undertaken to evaluate the role of nutritional factors as tools to enhance the immune parameters in the mucus of Senegalese sole (Solea senegalensis). Homogenous groups of Senegalese sole (initial body weight: 92.8 ± 1.52g) were fed: a control diet (CTRL); the CTRL diet supplemented with vitamin C (1000 mg/kg) (VIT C); and a diet identical to CTRL but in which 70% of the dietary fat was originated from coconut oil (COC), identified as a potential immunostimulant. After a period of 4 and 6 weeks of experimental feeding, fish mucus was sampled for quantification of lysozyme, alkaline phosphatase, proteases, lipid antioxidation (TBARS) and antimicrobial activity. Growth performance and lysozyme activity was not affected by dietary treatments, while the proteolytic activity and lipid oxidation was affected positively by both dietary treatments. Alkaline phosphatase activity was only affected by diets rich in coconut oil. Epidermal mucus of sole showed antibacterial activity against a series of marine pathogen bacteria. Highest inhibitory action was associated to mucus extracts derived from coconut oil fed fish. The modulation of selected mucus immune parameters through dietary factors is possible in Senegalese sole. A four weeks period of feeding seems enough to induce such changes. Further research is needed to determine the processes associated to such modulation and evaluate to what extent these beneficial changes contribute to an enhanced immune response of sole.