Immunological responses and wound healing in the polychaete Eurythoe complanata (Annelida: Amphinomidae) exposed to copper

Abstract

Polychaetes exposed to 0.4 mg Cu⁺² L^–1 (2.14 mg CuSO₄ 5H₂O L^–1; 30% 96 h-LC₅₀) for seven days and control individuals were divided into three groups: the first two were sensitized and non-sensitized with Micrococcus lysodeikticus, and the third was sensitized with heat-killed yeast. Lysozyme activity was tested in the first two groups and phagocytosis in the third one. Lysozyme was measured at 2 h and phagocytosis 15 min after immune sensitization. The effect of copper on wound healing was also examined in the polychaetes. For this, the polychaetes exposed and not exposed to copper were cut in two halves, and the body fragments were held in aquaria containing clean seawater, and the cicatrization was periodically observed. The lysozyme and phagocytosis responses were induced by the sensitization; however, these responses were inhibited after the metal exposure. On the other hand, 60–80% of the body fragments from the control group healed within four days, whereas the copper-treated individuals did not show cicatrization in the same period of time. In conclusion, the inhibition of the experimental activation of lysozyme and phagocytosis, and of wound healing in the polychaete Eurythoe complanata exposed to acute copper exposure, suggests the metal´  s potential toxicity on the physiological mechanisms that modulate the innate immunity in annelids, whose alteration could affect their tolerance to microbial infection.