Figure 5: Octopus Excretory System: afb: afferent branchial vessels, efb: efferent branchial vessels, vec: vena cava, bht: branchial heart, efb: efferent branchial vessels, ven: ventricle, aao: anterior aorta, res: renal sac, vec: vena cava, bha: branchial heart appendage, bht: branchial heart, rap: renal appendages, rsp: renal sac pore. (Martin, 1983).