Endangered Species: Mussels and Clams

A Christiansburg Elementary School Project
Submitted by Andrew of Christiansburg Elementary School
Christiansburg, Virginia, U.S.A.

clams
Clam
This image courtesy of Montana State University Dept. of Biology
Photographer Unknown
clam art
Original artwork by Andrew
This original report may be found
on the Radical Report Resources
pages completed by the Web Weavers
of Christiansburg Elementary School.
Why Study This Topic? What Was Already Known Search for Information Description of Plant or Animal Habitat Requirements
Adaptations Reasons for Endangerment Restoration Actions What Was Learned Conclusions from Research

Why Study This Topic?

  I chose to research mussels and clams because they looked the most interesting of the choices.

  There were several things about these animals that I wanted to learn. I wanted to find out what they ate and how they caught their food. I also wanted to know why they are endangered and how many species are endangered in Virginia.
 

What Was Already Known

  I hardly knew anything about the clams and mussels in Virginia before I started researching. I knew that they had a hard shell and a soft inside. I also knew that they lived on the bottom of an ocean or river.

Search for Information

  I searched in library books, on CD-ROMS, and the Internet for information.

  I soon learned that there was little information to be found. I had a lot of trouble getting information and also had trouble getting information I could understand. My father and I read the article from class together, and he explained the parts I did not understand.

Description of Plant or Animal

  Freshwater clams and mussels belong to the class bivalvia. If you want to be able to tell mussels apart, there are several things to look for. The shape of the shell, and the structure and position of the teeth are important. Also the color, texture of the surface, and the sculpture of the beak are important. It is difficult for most people to tell mussels and clams apart. Only the most experienced scientists can do it.

  In the past, malacologists (scientists who study clams and mussels) have disagreed about the names of freshwater mussels since the early 1900s. This has caused a lot of confusion in trying to study them. In trying to solve this problem the American fisheries Society has published a list of acceptable scientific names for freshwater mussels. This should help them keep mussels straight.

Habitat Requirements

  Most species of freshwater mussels live in runs and riffles of moderate size streams to large rivers. They live best where the bottom is a mixture of cobble, gravel, sand, and silt. They also like clean, fast moving water.

Adaptations

  Mussels have an interesting life cycle. There are male and female mussels. The male mussel releases sperm that enters the female during the spawning period. The eggs are fertilized inside the female and develop into parasitic larvae called glochidia. The glochidia are released into the water and attach to fish. They live on the fish for about three weeks. Then they drop off when they become juveniles and can live freely. Since mussels are immobile this is the only way they can spread. Some species of mussels may live fifty years or more.

Reasons for Endangerment

  According to my research little is known about freshwater clams. There are probably 38 species of freshwater clams in North America and about 17 species in Virginia. Scientists have not collected or studied them much. In Virginia, most species seem to live in sandy bottomed streams that flow over igneous rocks. There is so little known about them that it is uncertain if any of the species are endangered.

  There are 73 species of freshwater mussels in Virginia. Twenty-eight of those species are endangered and six species are threatened with extinction. There are some species of mussels that used to live in Virginia, but no longer can be found there. Those species include the acorn shell, narrow catspaw, round pigtoe, pink mucked, and the cumberland bean. These species can still be found in other states. Most mussels on the endangered or threatened species list come from the upper Tennessee river drainage in southwestern Virginia.

  About 30 species of freshwater mussels in Virginia are endangered. As with most endangered plants and animals, loss of habitat is what is threatening the mussels in Virginia. There are three main things that have affected their habitats. First, the stream habitat has changed. This is due mostly to channelization and dredging of streams. Second, there is a decrease in the water quality of Virginia's rivers and streams. This is caused by pollution, toxic spills, and sedimentation. Third, there is destruction of the riparian habitat. This is the habitat along the stream and river banks is destroyed. The mussels' habitats are changed by erosion and cutting of vegetation along the stream bank. The habitat of freshwater mussels in Virginia has been affected since the first settlers arrived. Then they began to clear the forest and started agriculture activities that adversely affect stream and river habitats.

  Since freshwater mussels are attached to the bottom of the streams, this makes them immobile. When there habitat changes, they are unable to move to a better habitat like other species. This makes mussels especially vulnerable to these changes in their environment.

  Another threat to freshwater mussels in Virginia is the Asian clam. Over the last 10 years, it has been introduced in every major river system in Virginia. They are competing with the native freshwater clams and mussels for habitat survival. The Asian clam is now the dominant mollusk in many rivers. It is not known if the native mollusks will be able to coexist with this species.

Restoration Actions

  No information provided for this section.

What Was Learned

  My research shows that too little is being done to help these animals. The most important thing that is going on is that mussels and clams are being collected and identified. This will help scientists figure out how big the problem of mollusk endangerment is. It will also help them in the future try to save this important inhabitant of our streams and rivers.

Conclusions From Research

  No information provided for this section.
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© copyright 1997 Christiansburg Elementary
Last updated on March 7, 1998