Fig. 1.

Overview of Riftia pachyptila body plan anatomy, phylogenetic placement, and mitochondrial genome. (A) Phylogenetic placement of Riftia pachyptila within Lophotrochozoa. Riftia together with Lamellibrachia form the clade Vestimentifera, a group of marine animals living in chitinous tubes and lacking a digestive tract. Animal silhouettes were downloaded from http://phylopic.org/. Tree topology was obtained through phylogenomic analysis. (B) Schematic drawing of Riftia pachyptila. The first part of the body, the obturacular region, contains the highly vascularized plume, whereas the head, heart, and gonads are located in the second body part, the vestimentum. The trunk region, third body part, harbors the trophosome (organ that houses the symbiotic bacteria), and the body wall (skin). The posterior part, the opisthosoma is the fourth and last body region of the tubeworm. Schematic drawing was modified from Nussbaumer et al. (2006). (C) Schematic representation of Riftia pachyptila mitochondrial genome, including the complete control region. CG-content and tRNA genes are represented by the blue histograms and boxes, respectively.