The Bivalve Tree of Life

2011 REU Intern Hannah Wirtshafter


Junior Biological Sciences major at Carnegie Mellon University

REU Mentors: Dr. Rüdiger Bieler (Curator, Zoology, Invertebrates) and Dr. Sid Staubach (Postdoctoral Fellow, Zoology, Invertebrates)

Symposium Presentation Title: Flexing our Mussels: Comparative Bivalve Gill Morphology

Symposium Presentation Abstract: The dual-shelled bivalves are arguably the most widely used class of mollusks: their organs are used for food, their pearls for jewelry, and their shells for decoration. Despite their many uses, detailed morphological analysis using modern techniques has not been thoroughly carried out on the majority of known species. The aim of the NSF funded BivAToL project is to assemble the bivalve tree of life, using morphological and molecular data. Within our study, I used scanning electron microscopy to analyze the gills and labial palps of 25 species of bivalves, with a focus on the superorders Pteriomorphia and Palaeoheterodonta. The gills and labial palps, which are essential for feeding, reproduction, and respiration, are an important character complex for determining phylogeniesdue to their high complexity and variability. Gill and labial palp novel character states were then identified and the species morphology was analyzed and specific characters were traced on recent phylogenies. The comparative analysis was then used to reconstruct a morphological phylogeny and to postulate a hypothesis on the evolutionary history of the gill and labial palp complex, which was then compared with evolutionary trees obtained through DNA sequence data.

Original Project Description: This project (see also is a part of the Assembling the Tree of Life initiative, a large research effort sponsored by the National Science Foundation to reconstruct the evolutionary origins of all living things. The BivAToL effort uses hundreds of selected target species from around the world and studies their morphology, anatomy, ultrastructure, and genetic makeup.

Research methods and techniques: REU participants in the project will receive an introduction to bivalve morphology and systematics. Participants will dissect and prepare specimens for microscopy, document diagnostic characters with optical and scanning microscopy, and gain experience with relevant literature research and collection management techniques. Time permitting, various histological techniques (in Field Museum’s histology laboratory) and 3-D computer reconstruction will become part of the training experience.