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.

To prevent over-exploitation of global fish stocks by the aquaculture industry, interest is growing in the identification of nontraditional species with potential value as fish feed. In this study, we investigated the biochemical composition of the polychaete Sabella spallanzanii . Its elemental composition, gross protein and proximate composition, amino acid composition, total lipid and fatty acid content, glycosaminoglycan (GAG) content and the extent of polychlorinated biphenyl contamination were determined over an annual cycle. Sabella spallanzanii showed particularly high gross protein (54.8 ± 5.8%) and gross energy (4.89 ± 0.5 kcal/g) content. All samples had high concentrations of Na, K, Ca, and Cl. Saturated fatty acids were higher than monounsaturated and polyunsaturated ones. A low ω-6/ω-3 ratio (1.7) was recorded. Our results suggest that S. spallanzanii can be used as a dietary supplement for farmed fish. The high concentrations of certain amino acids that improve potential palatability for many farmed fish species suggest that S. spallanzanii extracts can be used in artificial fish diets as an attractant. A further original aspect highlighted by this study is the high concentration of GAGs, which are useful in pet nutrition and also in the nourishment of farmed fish with a partially cartilaginous skeleton.

Although mucus plays many different roles among marine invertebrates, relatively little is known about the link between biochemical structure and function. In the present study we focused on some physical and chemical properties of the polychaete Sabella spallanzanii's mucus such as viscosity, osmolarity, electrical conductivity, elemental composition, the protein and carbohydrate content, the total lipids and fatty acid composition, and polychlorinated biphenyls (PCBs) contamination. Moreover, an antimicrobial activity of the mucus was investigated. The water content of S. spallanzanii mucus was 96.2+0.3%. By dry weight 26+1.2% was protein, 8+0.21% was carbohydrate and only 0.1% lipid, much of the remainder of the dry weight was inorganic (about 65.2%). The estimated PCBs content was ,0.005 mg g 21 . The mucus of S. spallanzanii exerted a natural lysozyme-like activity and produced in vitro the growth inhibition of Vibrio anguillarum, Vibrio harveyi, Pseudomonas aeruginosa and Candida albicans. The findings from this study contribute to improve the limited knowledge available on the mucus composition in invertebrates and have implications for future investigations related to employment of S. spallanzanii mucus as a source of compounds of pharmaceutical and marine technological interest.

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