Coelomoducts in Polyplacophora

In Polyplacophora the coelomoducts divide in the region of coelomostome and the gonadal cavities become closed off from pericardial coelom. The excretory coelom stay connected with pericardial coelom. In gastropods there is a marked asymmetry in the coelomic complex. The left gonad disappears and the right gonad opens into coelomoducts which has lost its renal function and its connection along with the pericardial coelom. The excretory organ is present only on one side (left kidney) and which is large and thick walled. In prosobranchs, the excretory opening is in the posterior part of mantle cavity and in pulmonates it opens outside the mantle cavity. In lamellibranchs, hence the complications of asymmetry in gastropods do not exist; the genital and renal ducts get separated. In the primitive group protobranchs, the whole coelomoducts has an excretory function. The gametes are discharged into renal organs. In filibranchs the coelomoducts is bent into a "U" shaped structure, the lower limb being glandular and the much more distal upper limb forms a bladder. The connection has shifted to the posterior end of the kidney. In eulamellibranchs, the two organs have developed separate openings. In cephalopods as well the separation of genital and excretory components of the coelomic complex has been acquired. The genital duct comes to run separately from the Reno - pericardial canal and kidney.