The ultrastructure of calcareous cirratulid (Polychaeta, Annelida) tubes

The entire tube wall of Dodecaceria caulleryi and D. coralii is composed of thin calcareous lamellae with a spherulitic prismatic ultrastructure. In Diplochaetetes mexicanus the tube ultrastructure is similar, but contains also some lamellae with a homogeneous structure. The biomineralization system of cirratulids has not evolved since the appearance of calcareous tubes in the Oligocene. The tube ultrastructure of cirratulids shows the strongest similarity to that of sabellids.