Chaetopterus tubes: Ultrastructural architecture.

The wall of the tube 'house' constructed by the polychaetc, Chaelopterus variopedatus, was examined by scanning and transmission electron microscopy and polarizing and phase-contrast light microscopy. The tube wall consists of alternating plies of aligned protein fibres imbedded in an unstructured matrix. The protein fibres range in diameter from 50-400 mmu and have an axial periodicity of about 641 A. The relative proportion of fibres to matrix, the total number of plies, and the number of fibres per ply vary throughout the tube.