A brief review of the immunobiology of Eledone cirrhosa

Abstract

Blood can be sampled repeatedly from the lesser octopus Eledone cirrhosa (Lamarck) and the haemocytes cultured for up to 72 h. Sampling results in an increase in the number of circulating haemocytes per ml and in the percentage of haemocytes containing cytoplasmic granules, and a change in the staining pattern of the haemocytes. It also causes a decrease in the quantity of copper in the haemolymph. The haemocytes phagocytose bacteria (Vibrio anguillarum) in vitro in the absence of haemolymph, but there is enhanced phagocytosis in the presence of haemolymph. Haemocytes migrate towards low concentrations of various blood preparations, to lipopolysaccharide (LPS) and to preparations that had contained live bacteria. They also have an apparent bacteriostatic effect on the growth of live bacteria. Haemocytes produce intracellular reactive oxygen species after incubation with dead bacteria in particular, but also live bacteria and LPS. E. cirrhosa haemolymph agglutinates the bacteria V. anguillarum, V. parahaemolyticus and Aeromonas salmonicida and exerts a bacteriostatic effect on them. The haemolymph, haemocytes and certain tissues from E. cirrhosa exhibit lysozyme and antiprotease activity. Injection of live V. anguillarum causes an increase in lysozyme activity in the branchial heart (after 48 h) and a decrease in the number of circulating haemocytes (after 24 h). Antiprotease activity increases in the haemocytes (4 h) after injection of bacteria but decreases in the haemolymph. Live bacteria cause an increase in the number of circulating haemocytes, but are cleared from the circulation in about 4 h by both the haemocytes and tissues (branchial heart, branchial heart appendage and white body), where they are degraded. Ultrastructural changes were observed in the branchial heart cells and the haemocyte nucleus after injection of bacteria. Following injection, colloidal graphite is aggregated in blood vessels only.