Tryptophan participates on several physiological mechanisms of the neuroendocrine-immune network and plays a critical role in macrophages and lymphocytes function. This study intended to evaluate the modulatory effects of dietary tryptophan on the European seabass ( Dicentrarchus labrax ) immune status, inflammatory response and disease resistance to Photobacterium damselae piscicida . A tryptophan deficient diet (NTRP); a control diet (CTRL); and two other diets supplemented with tryptophan at 0.13% (TRP13) and 0.17% (TRP17) of feed weight were formulated. Fish were sampled at 2 and 4 weeks of feeding and the remaining were i.p. injected with Phdp (3 × 10 6 cfu/fish) at 4 weeks and the inflammatory response (at 4, 24, 48 and 72 hours post-infection) as well as survival were evaluated. Results suggest that fish immune status was not altered in a tryptophan deficient scenario whereas in response to an inflammatory insult, plasma cortisol levels increased and the immune cell response was compromised, which translated in a lower disease resistance. When dietary tryptophan was offered 30% above its requirement level, plasma cortisol increased and, in response to bacterial infection, a decrease in lymphocytes, monocytes/macrophages and several immune-related genes was observed, also compromising at some degree fish disease resistance.

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Presently, there is a high demand for nutritionally enhanced foods, so it is a current challenge to look at new raw food sources that can supplement beneficially the human diet. The nutritional profile and key secondary metabolites of red seaweeds (Rhodophyta) are gaining interest because of this challenge. In this context, the possible use of the red seaweed Chondracanthus teedei var. lusitanicus (Gigartinales) as a novel nutraceutical source was investigated. As a result, we highlight the high mineral content of this seaweed, representing 29.35 g 100 g−1 of its dry weight (DW). Despite the low levels of calcium and phosphorus (0.26 and 0.20 g 100 g−1 DW, respectively), this seaweed is an interesting source of nitrogen and potassium (2.13 and 2.29 g−1 DW, accordingly). Furthermore, the high content of carbohydrates (56.03 g 100 g−1 DW), which acts as dietary fibers, confers a low caloric content of this raw food source. Thus, this study demonstrates that C. teedei var. lusitanicus is in fact an unexploited potential resource with the capability to provide key minerals to the human diet with promising nutraceutical properties.