Sourced from Ezhova et al. (2015). Interrelations between different coeloms (a) and haemocoel structures (b) in the axial complex of Ophiura robusta. Capital letters indicate the radii. amp -Madreporic ampulla, ap- axial part of axial organ, apc -axocoelomic perihaemal ring, axc -axial coelom, ght -gastric haemal tufts, gn -gonads, gnb -genital haemal ring, gnc -genital coelom, grb -gastric haemal ring, orb -oral haemal ring, pc -pore canal, pcd -“pericardial” coelom, poc -perioral coelom, ppf -mesh (aboral) region of “pericardial” part of axial organ, pps -swollen (oral) region of “pericardial” part of axial organ, sc -stone canal, spc -somatocoelomic perihaemal ring, wr -ambulacral ring.