Synthesis and maturation processes in the exoskeleton of the vent worm Riftia pachyptila

Abstract

To investigate tube-wall maturation in Riftia pachyptila, tube-secretion experiments were performed on live individuals in pressurized aquaria during “HOT 96” cruise (East Pacific Rise, February and March 1996). Two major biochemical components of the tube, i.e. chitin and proteins, were measured during the process of tube maturation. Mean chitin and protein contents were two-fold lower in fresh (i.e. newly secreted) tube-walls than in mature tube-walls. Chitin content is related to age, i.e. to the time elapsed since the fresh tube material was extruded, and can thus provide a marker for determining tube maturation status. In contrast, variations in protein content suggest a difference in the nature of the secretion products in the upper and basal regions of the exoskeleton. The tube-secretion experiments analyzed the protein profiles of both fresh-tube material and actively secreting tissues. A protein triplet with an apparent molecular weight of ∼28 kdaltons proved useful as a marker for tracing exoskeleton protein synthesis and secretion pathways.