While unionoids are diverse and conspicuous members of freshwater communities all over the Earth, they are often ignored or unknown to everyone except specially trained invertebrate zoologists. This is extremely unfortunate since these animals are interesting, endangered and valuable for studying the process of evolution. This series of "About" pages is intended to provide some of the biological background on freshwater mussels. We can provide a little background information and sources, including other web sites, where more detailed information can be obtained. Two excellent (we think) generally sources of information about freshwater mussels are:
Both of these resources are available on-line.
More specialized information about our current research is discussed on this web site under the headings of Taxonomy (i.e., species- and genus-level diversity) and Systematics (i.e., classification and relationships).
Mollusca: Bivalvia
 Unionoids, that is, members of the Order Unionoida, are commonly referred to as freshwater mussels, freshwater pearly mussels or naiades.
The Order Unionoida is a part of the group of invertebrates called mollusks; specifically they are bivalves, like clams, true mussels, oysters and scallops. In fact, freshwater mussels are most closely related to a cockle-like marine bivalve call Neotrigonia. Click here to find out about the different major groups of mollusks. Click here to learn more about where freshwater mussels fit on the Tree of Life and the characteristics that freshwater mussels share with other Bivalvia. |
Conservation
 In the United States and in countries around the world, the diversity of the Unionoida is declining, and this has brought a great deal of conservation attention to freshwater mussels. River invertebrates, including unionoids, have suffered greatly from pollution, damming and over-harvesting. Specifically, freshwater mussels, before plastic, were the things from which buttons were made! Click here to find out more about the imperiled status of freshwater mussels.
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Life History
 In most respects, unionoids are similar to many marine bivalves: as adults they are sessile filter-feeders. However, freshwater mussels have a fascinating life history that involves parental care and, instead of the stereotypical planktonic veliger larvae of their salt-water cousins, freshwater mussels are parasitic on fish during their larval stage. It is while attached to their obligate host that a freshwater mussel completes its metamorphosis. Click here to get more details of the unionoid life cycle.
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Evolution
 Over the last 100 years, most research on the Unionoida has focused on ecology and conservation. While these lines have contributed a large amount of data on how contemporty process influence mussel distributions and, especially, on the details of many aspects of their life cycle, this recent buzz of work has tended to overshadow the facts that
- mussel evolution and diversity have been greatly influenced by their evolutionary history and
- that history is long and very interesting.
Click here to learn why we think the evolution of the Unionoida is a topic worth studying. |
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