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- How increasing temperature affects the innate immune system of sea urchin paracentrotus lividus (Lamarck, 1816) reared in a RAS systemPublication . Rodrigues, Ana Filipa; Lourenço, Sílvia; Gomes, Ana Sofia; Tchobanov, Carolina F.; Pombo, Ana; Baptista, TeresaThe purple sea urchin, Paracentrotus lividus, is the most exploited and economically important in Southern Europe due to the high value of its gonads. Temperature generally affects several physiological functions of marine invertebrates and the ocean warming has been linked to increasing frequency and severity of disease outbreaks in several echinoderms. Sea urchins have an innate immune system consisting of coelomocytes, the cellular components responsible for the immune response, supported by proteases and lysozymes. The present study aimed to investigate the effect of increasing seawater temperature on the immunological response of P. lividus. In this experiment, the animals were exposed to an increase in temperature up to 24 degrees C for 36 days, after which cellular and humoral immunity parameters were measured. The number of coelomocytes in the animals increased with the temperature rise, mainly the phagocytes and the colourless granulocytes. In the humoral response of the animals, only the concentration of lysozyme responded to the increase in temperature.
- Activation profile of the Atlantic salmon (Salmo salar) calcium-sensing receptor (Casr) by selected L-amino acidsPublication . Gomes, Ana Sofia; Gélébart, Virginie; Félix, Rute; Cardoso, João; Zimmermann, Fabian; Lai, Floriana; Power, Deborah Mary; Ronnestad, IvarIn mammals, the calcium-sensing receptor (CaSR) is involved in nutrient sensing and modulated by several amino acids. In teleosts, sequence homologues of the mammalian CaSR have been described but their function in sensing amino acids remains elusive, including in Atlantic salmon (Salmo salar), an important aquaculture species. This study investigated the activation of Atlantic salmon Casr (asCasr)-mediated signaling pathways-Gq, Gi, and ERK1/2-by six selected L-amino acids (histidine, tryptophan, phenylalanine, isoleucine, leucine and valine) and by Ca2+. Using a Flp-In-HEK293 cell line stably expressing asCasr, we confirmed activation of all three pathways. L-histidine, L-phenylalanine, and L-tryptophan triggered Gi signaling independent of Ca-2(+). Notably, no Ca-2(+) concentrations induced Gi activation, but IP1 production increased in a concentration-dependent manner. L-histidine was the only amino acid to activate the Gq pathway without Ca-2(+), and this response was amplified by the presence of Ca-2(+). In the presence of 2.5 mM Ca-2(+), L-phenylalanine and L-tryptophan also activated Gq signaling in a concentration-dependent manner. Additionally, in the presence of 10 mM Ca-2(+), L-histidine, L-phenylalanine, and L-tryptophan triggered ERK phosphorylation. These findings establish asCasr as a functional homologue of mammalian CaSR, activated in a concentration-dependent manner by L-amino acids with an aromatic ring.
- Dietary supplementation with algae-based ingredients modulates antioxidant defenses and immune response in sea urchin Paracentrotus lividus following a Vibrio parahaemolyticus challengePublication . Rodrigues, Ana Filipa; Lourenço, S.; Gomes, Ana Sofia; Vaz, M.; Cardoso, H.; Violante, A. P.; Baptista, T.Functional diets are increasingly recognized as an important strategy to enhance health and production performance in sea urchin aquaculture. This study evaluates the effects of diets containing algae-based ingredients with different carotenoid pigment profiles on the immune and antioxidant systems of the sea urchin Paracentrotus lividus. During a 60-day nutritional trial, sea urchins were fed one of three diets that differed in both ingredient matrix and pigment profile: 1) a base diet formulated without algae and low in carotenoid pigments; 2) a formulated pumpkin/algal diet supplemented with Nannochloropsis sp. and high in β-carotene (nanno diet); and 3) a kelp diet based on Saccorhiza polyschides containing a mixture of carotenoid pigments and representing the natural diet of P. lividus. The effects of diets on oxidative stress response were assessed by quantifying catalase (CAT) and superoxide dismutase (SOD) activities and lipid peroxidation (LPO). The effect of diets on the short-term immune response was assessed using a time-course challenge with Vibrio parahaemolyticus at the end of the feeding trial. Sea urchins fed the kelp diet showed the strongest antioxidant defenses, while sea urchins fed the base diet presented higher LPO. After the pathogen challenge, total coelomocyte density was not significantly affected by diet. However, significant diet-dependent changes were observed in specific coelomocyte populations, including colorless granulocytes, red granulocytes and vibratile cells. Sea urchins fed the kelp diet exhibited a more pronounced immune activation, characterized by higher concentrations of lysozyme. In conclusion, supplementing diets with algae rich in carotenoids and other bioactive compounds may enhance sea urchin immune defenses against pathogens and improve resistance to oxidant stress. These findings support the development of functional diets for sea urchin aquaculture aimed at promoting health and resilience under culture conditions.