c1035.txt

As adults, these worms lack a functional digestive system and rely on microbial endosymbionts for their energetic needs. Like other siboglinids, adult R. pachyptila lack a gut, mouth, anus, and conventional feeding ability and possesses bacterial symbionts. (Hilário et al. 2011). Adult R. pachyptila are nourished entirely by sulfur-oxidizing endosymbiotic bacteria (Coykendall et al. 2011). Although the larvae of R. pachytila are symbiont-free and possess a transient digestive system, these digestive structures are lost during development, resulting in adult animals that are nutritionally dependent on their bacterial symbionts. Thus, each generation of tubeworms must be newly colonized with appropriate symbionts. (Nussbaumer et al. 2006)