IDENTIFICATION OF THE ANTIMICROBIAL ACTIVITY FROM OCTOPUS VULGARIS HAEMOCYTES.

The marine environment comprises complex ecosystems and many of organisms are known to possess bioactive components as a common means of self-defence or for the protections of eggs and embryos. Lately, many bioactive compounds have been extracted, characterized and purified from various marine animals like tunicates, sponges, corals, and molluscs (Rajasekharan et al. 2011). Among cephalopods, the only studies involving bioactive peptides with antimicrobial activity (AMPs) are those conducted in squids and cuttlefish. They leave their eggs to fend for themselves and interestingly they do not get any infections. The eggs release polypeptides, sexual pheromones and AMPs trapped in the egg capsule, mainly expressed by female accessory sex gland that confers to them an efficient protection against microorganisms. Cephalopods, unlike other molluscs, have a closed circulatory system. The blood consists of haemolymph, haemocyanin and haemocytes (Novoa et al 2002). In this study we have focused the attention on the morphological and functional characterization of the haemocytes, from Octopus vulgaris, as the first responsible of the innate immunity. Three major haemocytes types were identified by light microscopy (hemoblast-like cells, hyalinocytes and granulocytes) based on nucleus/cytoplasm ratio and the presence or absence of cytoplasm granules. The haemocytes were cytochemically characterized for the presence of different activities responsible of the humoral response (phenoloxidase, peroxidise, phagocytosis). We have evaluated the bactericidal activity of haemocytes in the presence of different bacteria strains, using the method of the plate radial diffusion (Bauer et al 1996). We have also evaluated the activity of a methanolic acid extract of these cells, using the disc diffusion method and the minimum inhibitory concentration (MIC), in order to investigate the presence of soluble biotic compounds responsible of the antibacterial activity. Identifying the bioactive compounds could lead to many applications in fields such as halieutics and ecology (sexual pheromones), animal feeding (AMPs in pet food and aquaculture pellets), aquaculture and healthcare (AMPs).