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Sea anemones are valuable for therapeutic research as a diversified source of bioactive molecules, due to their diverse bioactive molecules linked to predation and defence mechanisms involving toxins and antimicrobial peptides. Acid extracts from Actinia equina tentacles and body were examined for antibacterial activity against Gram-positive, Gram-negative bacteria, and fungi. The peptide fractions showed interesting minimum inhibitory concentration (MIC) values (up to 0.125 µg/mL) against the tested pathogens. Further investigation and characterization of tentacle acid extracts with significant antimicrobial activity led to the purification of peptides through reverse phase chromatography on solid phase and HPLC. Broad-spectrum antimicrobial peptide activity was found in 40% acetonitrile fractions. The resulting peptides had a molecular mass of 2612.91 and 3934.827 Da and MIC ranging from 0.06 to 0.20 mg/mL. Sequencing revealed similarities to AMPs found in amphibians, fish, and Cnidaria, with anti-Gram+, Gram-, antifungal, candidacidal, anti-methicillin-resistant Staphylococcus aureus, carbapenemase-producing, vancomycin-resistant bacteria, and multi-drug resistant activity. Peptides 6.2 and 7.3, named Equinin A and B, respectively, were synthesized and evaluated in vitro towards the above-mentioned bacterial pathogens. Equinin B exerted interesting antibacterial activity (MIC and bactericidal concentrations of 1 mg/mL and 0.25 mg/mL, respectively) and gene organization supporting its potential in applied research.

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Global warming and connected acidification of the world ocean attract a substantial amount of research efforts, in particular in a context of their impact on behaviour and metabolism of marine organisms, such as Cnidaria. Nevertheless, mechanisms underlying Cnidarians' neural signalling and behaviour and their (possible) alterations due to the world ocean acidification remain poorly understood. Here we researched for the first time modulation of GABAA receptors (GABAARs) in Actinia equina (Cnidaria: Anthozoa) by pH fluctuations within a range predicted by the world ocean acidification scenarios for the next 80-100 years and by selective pharmacological activation. We found that in line with earlier studies on vertebrates, both changes of pH and activation of GABAARs with a selective allosteric agonist (diazepam) modulate electrical charge transfer through GABAAR and the whole-cell excitability. On top of that, diazepam modifies the animal behavioural reaction on startle response. However, despite behavioural reactions displayed by living animals are controlled by GABAARs, changes of pH do not alter them significantly. Possible mechanisms underlying the species resistance to acidification impact are discussed.

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Marine species represent a great source of biologically active substances; Actinia equina (AE), an Anthozoa Cnidaria belonging to the Actinidiae family, have been proposed as original food and have already been included in several cooking recipes in local Mediterranean shores, and endowed with excellent nutraceutical potential. The aim of this study was to investigate some unexplored features of AE, through analytical screening and an in-vitro and in-vivo model. An in-vitro study, made on RAW 264.7 stimulated with H2O2, showed that the pre-treatment with AE exerted an antioxidant action, reducing lipid peroxidation and up-regulating antioxidant enzymes. On the other hand, the in-vivo study over murine model demonstrated that the administration of AE extracts is able to reduce the carrageenan (CAR)-induced paw edema. Furthermore, the histological damage due to the neutrophil infiltration is prevented, and this highlights precious anti-inflammatory features of the interesting food-stuff. Moreover, it was assessed that AE extract modulated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) and The nuclear factor erythroid 2-related factor 2 (Nrf-2) pathways. In conclusion, our data demonstrated that thanks to the antioxidant and anti-inflammatory properties, AE extract could be used as a new food supplement for inflammatory pathology prevention.

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Theoretical models of animal contests such as the Hawk-Dove game predict that variation in fighting behavior will persist due to mixed evolutionarily stable strategies (ESS) under certain conditions. However, the genetic basis for this variation is poorly understood and a mixed ESS for fighting can be interpreted in more than one way. Specifically, we do not know whether variation in aggression within a population arises from among-individual differences in fixed strategy (determined by an individual's genotype-direct genetic effects [DGEs]), or from within-individual variation in strategy across contests. Furthermore, as suggested by developments of the original Hawk-Dove model, within-individual variation in strategy may be dependent on the phenotype and thus genotype of the opponent (indirect genetic effects-IGEs). Here we test for the effect of DGEs and IGEs during fights in the beadlet sea anemone Actinia equina. By exploiting the unusual reproductive system of sea anemones, combined with new molecular data, we investigate the role of both additive (DGE + IGE) and non-additive (DGE × IGE) genetic effects on fighting parameters, the latter of which have been hypothesized but never tested for explicitly. We find evidence for heritable variation in fighting ability and that fight duration increases with relatedness. Fighting success is influenced additively by DGEs and IGEs but we found no evidence for non-additive IGEs. These results indicate that variation in fighting behavior is driven by additive indirect genetic effects (DGE + IGE), and support a core assumption of contest theory that strategies are fixed by DGEs.

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The mucus produced by many marine organisms is a complex mixture of proteins and polysaccharides forming a weak watery gel. It is essential for vital processes including locomotion, navigation, structural support, heterotrophic feeding and defence against a multitude of environmental stresses, predators, parasites, and pathogens. In the present study we focused on mucus produced by a benthic cnidarian, the sea anemone Actinia equina (Linnaeus, 1758) for preventing burial by excess sedimentation and for protection. We investigated some of the physico-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, protein, carbohydrate, and total lipid contents. Some biological activities such as hemolytic, cytotoxic, and antibacterial lysozyme-like activities were also studied. The A. equina mucus is mainly composed by water (96.2% ± 0.3%), whereas its dry weight is made of 24.2% ± 1.3% proteins and 7.8% ± 0.2% carbohydrates, with the smallest and largest components referable to lipids (0.9%) and inorganic matter (67.1%). The A. equina mucus matrix exhibited hemolytic activity on rabbit erythrocytes, cytotoxic activity against the tumor cell line K562 (human erythromyeloblastoid leukemia) and antibacterial lysozyme-like activity. The findings from this study improve the available information on the mucus composition in invertebrates and have implications for future investigations related to exploitation of A. equina and other sea anemones' mucus as a source of bioactive compounds of high pharmaceutical and biotechnological interest.

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Pairwise contests occur when two individuals compete directly over ownership of an indivisible resource. Contests vary in the degree of escalation, some encounters being settled through non-injurious behaviour while others are only resolved after dangerous fighting. Here, we investigate the role of relatedness, assessed using AFLP analysis, on the occurrence of stinging during staged contests in the beadlet sea anemone Actinia equina. Contrary to our expectations, we found that the chance of stinging, and hence the chance of inflicting damage, increased with the degree of relatedness between the two opponents. This result may be explained by the negative relationship between asymmetry in fighting ability and escalation level predicted by theory. We suggest that in order to fully understand how relatedness influences aggression, predictions from kin selection theory should be incorporated with those from contest theory.

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