Sea urchins are invertebrates that play a crucial role in marine ecosystems by controlling benthic algal communities and whose natural populations are being affected by different biotic and abiotic factors. Triggering physiological processes promotes the activation of certain metabolic pathways, so oxidative status markers could be a suitable tool to asses maturation stage in which natural populations are. Antioxidant status of three species of Mediterranean Sea urchins, A. lixula, P. lividus and S. granularis, was evaluated in gonadal and digestive tissue. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione s-transferase (GST), glucose 6-phosphate dehydrogenase (G6PDH), NAD(P)H: quinone oxidoreductase (NQO1) and lipid peroxidation were assayed. Significant differences were found among species, displaying in general higher antioxidant activity in A. lixula and S. granularis compared to P. lividus. A significant effect of sex was observed with females exhibiting a higher gonadosomatic index and higher levels of lipid peroxidation mainly in A. lixula. These results seem to be related to metabolic fluctuations associated with the gonadal maturation stage. Changes in digestive tissue were less evident, but some differences among species could be related to triggered digestive processes for replenishment of energy reserves in gonads. Oxidative status can be a useful complementary tool to evaluate gonadal condition in species of sea urchin from the same habitat. Integrative physiological and biochemical studies will contribute to the knowledge of invertebrate physiology.

Anemonia viridis is a species of sea anemone (Cnidaria:Anthozoa) currently experiencing negative environmental impacts on their natural populations in the Mediterranean Sea. This species has excellent regeneration capacity, such that asexual reproduction can be induced in captivity via longitudinal bisection, but there is no information about the impact of this procedure on the animal's physiology beyond short-term responses. The goal of this work was to assess the stress response of A. viridis during and after regeneration. We measured oxidative and immunological state markers in control and bisected anemones, at 4 weeks post-injury and 20 weeks post-injury. We then performed Principal Component Analysis (PCA) to identify trends at the multivariate level. Additionally, we carried out a histological evaluation of the wound healing process during the first 7 days post-injury. Higher antioxidant enzymatic activity was found in bisected anemones, mainly in catalase and gluthathione-dependent enzymes. This response was often reverted by 20 weeks post-injury in tentacles. No differences in lipid peroxidation were observed. Phosphatase activities were unaltered within the studied time-frame. Histological analysis indicated recruitment of amoebocytes, the immune effector cells in anthozoans, and appearance of fibrillar mesoglea, detectable between 6 h and 24 h post-bisection. Results suggest the antioxidant response was effective containing oxidative damage. Longitudinal fission appears to be a viable technique for inducing asexual reproduction in A. viridis without triggering a stress response, and could reduce dependence of the market on the natural environment.