“…The ascidian POs are copperdependent orthodiphenoloxidases (Kahn, 1985;Sugumaran et al, 1988) that were at first identified by histochemical reaction in the tunic hemocytes (Barrington and Thorpe, 1968), suggesting a quinone-tanning system involved in the production of tunic scleroprotein (Chaga, 1980). Circulating hemocytes from naïve ascidians can exert in vitro PO-dependent cytotoxic activity versus erythrocytes and tumor cell lines (Cammarata et al, 1997;Arizza et al, 2011), whereas LPS inoculation activates the proPO pathway, and enhanced PO activity (Jackson et al, 1993;Cammarata and Parrinello, 2009). In non-fusion reaction of colonial ascidians, the enzyme mediates the formation of the cytotoxic foci along the contacting regions of genetically incompatible colonies (Hirose et al, 1990;Ballarin et al, 1998;Shirae and Saito, 2000;Shirae et al, 2002;Cima et al, 2004;Zaniolo et al, 2006).…”