Аннотация:The giant dimensions of vestimentiferan Riftia pachyptila (Jones, 1981) are achieved thanks to thewell-developed vascular system. In the vestimentum, there is a complicated net of lacunae, includ-ing the brain blood supply and the ventral lacuna underlying the ciliary field. The trunk region hasan extensive network of blood vessels feeding the gonads («rete mirabile»). The thick muscular lin-ing of the mesenterial vessels in the trunk and the dorsal vessel in the opisthosome serves as anadditional pump, pushing blood into numerous vessels in the segments. It was hypothesized thatthe blood envelope of the ventral blood vessel in the trunk provides the blood supply to the troph-osome. The 3D reconstruction has revealed that there are two vascular systems of the tentacularcrown of R. pachyptila. Blood runs into the tentacles via axial afferent vessels, as described earlieronly for Riftia, and also via basal ones, as described for other vestimentiferans except Riftia.Thebasal ones are poorly developed, and the number of lamellar blood vessels is small, indicating alack of demand for these within huge R. pachyptila. It appears that the presence of these vesselsis the preserved ancestral state of Vestimentifera. In different portions of the dorsal vessel, themorphology of the intravasal body varies, depending on function.