Unionid Mussels
in Kansas

 Fall River mussels Verdigris River mussels
L-R: Bleufer, Pistolgrip and a young Pocketbook
from the Fall River near New Albany, Kansas
Photo by Jim Mason

Clockwise from top: Neosho Mucket, Butterfly, Western Fanshell and Ouachita Kidneyshell.  All these species are on the threatened and endangered species list in Kansas.  They were found in the Verdigris River in Montgomery County, Kansas.
Photo by Ed Miller

bulletCharacteristics of Unionid Mussels
bulletOther types of freshwater bivalves
bulletMussel links
bulletMussel research
bulletList of Kansas' Unionid Mussels

Unionid Mussels:

bulletMussels are in the Family Unionidae, Class Bivalvia within the Phylum Mollusca.  Mollusks are a very diverse group that might not seem to be related.    Mussels are cousins to the squid, octopus, nautilus, snail and slug!
bulletUnionid Mussels (also known as naiades or freshwater mussels) have bilateral symmetry.  The two shell halves or valves are identical in size and proportions.  The only difference between the valves is in the structure of the area where the shells fit together.  The valves typically have two kinds of interlocking structures that serve to hold the shell together and protect its resident.  These are called lateral teeth and pseudocardinal teeth, and can be seen in the following images of a Mapleleaf.  The exact shape and size of these structures are important in keying out species.  The area between the lateral and pseudocardinal teeth is called the interdentum.   Collectively, these three features are called the hinge.
Pseudocardinal teeth
Pseudocardinal teeth of a Mapleleaf
Lateral Teeth
Lateral teeth of a Mapleleaf
bulletMussels can move, but verrrry slowly!  They have a muscular "foot" that they can protrude out between the valves, wedge into the substrate on the stream bottom and then contract to pull the animal a short distance.  This process is then repeated if the mussel wishes to move some more.  Mussels can use this method to either move sideways or vertically.  Some mussels can be fairly active.  Other species may spend their whole lives in one spot.  One fun thing to do is look for the mussel trails of the "frisky" types in shallow water.  The trails resemble what you would see if you took a stick and drew a squiggle with it.  If you follow the trail, you will find the animal at one end or the other, usually in a small depression. 
bulletMost species of mussels have a parasitic stage of life that requires a suitable host fish.  The eggs develop within the female mussel in a specially modified gill pouch called the marsupium. They are released as a larval form called glochidia, which must attach themselves almost immediately to either the gills or fins of the proper species of fish.  This apparently does no harm to the host fish.  Some unionids may use more than one species of fish as a host and others only a single species.   (One notable exception is the Salamander Mussel [Simpsonaias ambigua], which uses a type of salamander called the Mud Puppy for the host instead of fish.   Also, at least one species of unionid does not have a parasitic stage.)  The glochidia mature into juvenile mussels, burst out of their cyst and drop to the bottom to begin their adult life.  This is the principal means that unionid mussels use to disperse into new territory.  They have no other way to move upstream in a watershed, other than by the slow creeping action referred to above.

Several species of mussels have very interesting methods for getting a fish close enough to ensure they will be infected with glochidia.  Some wave a lure called a mantle flap, which usually looks like a small minnow, but in one species it resembles a crawdad!  When a predator fish tries to nab what it thinks is a meal, the mussel squirts a bunch of glochidia into its mouth!

Others carry deception a step further.  They form their glochidia into gummy little packets that look like tiny fish or aquatic insect larvae and release them into the water.  These packets are called conglutinates.   When a predator fish tries to eat this decoy, the conglutinate ruptures in its mouth, releasing the glochidia.

Super Conglutinate!
Super Conglutinate!

The ultimate in mussel trickery is called a super conglutinate!   This is made up of dozens of conglutinates formed into a larger shape that are attached to the mother mussel by a long mucous ribbon, which allows it to wave back and forth in the water - just like a fishing lure on the end of a line!  The tightly packed rows of conglutinates bear an incredible resemblance to the segmented appearance of some kinds of minnows.  Any fish that chomps down on one of these will REALLY get a dose of glochidia!

This photo shows the super conglutinate lure of Lampsilis perovalis, the Orange-Nacre Mucket.  It even has a lateral stripe and a "head"!  You can see more pictures of it on Dr. Chris Barnhart's web site listed in the links below, including a video of it waving in the current!

bulletMussels are filter feeders.  They pump water through themselves using two tubes called siphonsAs the water passes through the mussel, it gets oxygen and food.  As the water leaves, it carries away waste products and (in season) sperm and glochidia.  The siphons are located at the posterior end of the shell, which is at the end opposite the pseudocardinal teeth.  (The anterior end is the one closest to the pseudocardinal teeth.)  Mussels will always seek to orient themselves with the posterior end sticking out of the substrate so they can use their siphons properly.
bulletMussels may live over 100 years, although most live 20 to 30 years.  Generally, the thinner-shelled species live shorter lives, although they grow quicker.
bulletMussels are declining in North America.  Of the ~300 different species of mussels in North America, over 44%  are either extinct or in serious decline.  In Kansas, the figure is 60%.  No other class of animal or plant is in as much trouble.
bulletAs with most types of wildlife, habitat loss is the main problem.   Channelization and gravel dredging disrupts or eliminates the bottom substrate where the mussels live.  Excessive siltation from soil erosion smothers them.   Altered flow regimes below dams de-stabilize the natural continuity of bottom substrates.  Withdrawl of water from rivers for irrigation and other purposes can cause the rivers to go dry.  Damming a river into a lake or reservoir limits the number of mussel species that can survive there.
bulletWater pollution harms mussels, although the impact is hard to quantify.  They can be poisoned outright - just as fish can - by large doses of pollution.  But there are probably more subtle impacts through disrupting the reproductive cycle and killing off the fish hosts of their glochidia.
bulletOverharvest for human use has contributed to their decline in some cases. Many species of mussels were harvested heavily in the early 1900's.  Their shells were used to make buttons for clothing.  This harvest was unregulated and many species of mussels were severely impacted by it.  This business ended after the 1940's due to the invention of plastic buttons.
             Commercial harvesting began again around 1960.  This time the thicker-shelled species were the target.  Their shells were cut up and used as nuclei for cultured pearls.  This market lasted through the mid-1990's.  Most states attempt to regulate this harvest through size and catch limits, but enforcement of the regulations is often difficult.   The market has fallen off in recent years in part due to the use of synthetic nuclei.
             In certain areas mussels are overharvested by people hoping to find freshwater pearls.  Few species of mussel produce pearls and most of the pearls produced are of poor quality.  In addition, the incidence of freshwater pearls is very small even in those species that are known to produce them (less than 4% at best).  Consequently, vast numbers of mussels are slaughtered for a very few pearls.  Some attempts have been made to culture freshwater pearls - with modest success - so hopefully this sustainable method will replace the extremely wasteful and illegal wild harvest.




Zebra mussels
Zebra mussel shells

Zebra stripes!
Close-up view showing the stripes
- Photos by Jim Mason

The zebra mussel (Dreissenia polymorpha)
is NOT a unionid mussel.  It is a dangerous new invasive species in North America.  While less than an inch in length, it has a tremendous reproductive rate and apparently no significant natural enemies in North America.  It's larvae are free-swimming and do not require an intermediate host.  They will attach to any hard surface, even each other.  Note the baby zebras that were growing on the adults in the picture to the left.  They are capable of completely obstructing water intakes at power plants and can smother native mussels by growing all over them.

Unfortunately, zebra mussels were discovered in Kansas in El Dorado Lake in August 2003 and in Winfield City Lake in December 2006.  It is essential that anglers, boaters and anyone else who engages in water sports in these lakes - or any other body of water that is infested with zebra mussels - exercise the utmost care to keep them out of other watersheds.

See the Mussel Bed for more information on the species in Kansas.

Click here to learn more about them and how you can help prevent the spread of this unwanted invader.

Click here for the Kansas Department of Wildlife, Parks & Tourism web page on zebra mussels.

Click here to download the brochure. Click the icon for the KDWP brochure on zebra mussels. (307K pdf file)

Fingernail Clams (Family Sphaeriidae) are also NOT unionid mussels.  
These are very small bivalves (<20 mm.) which are often found in streams.  
They are related to the Asiatic Clam, and have the same arrangement of the shell teeth. 
About 20 species are known from Kansas.  They are an important part of the aquatic food chain.
The Asiatic Clam (Corbicula fluminea) is also NOT a unionid mussel.  This small (< 1.5 inches) bivalve is found throughout much of North America.  While it does not pose the same economic threat as the Zebra mussel, it does compete for food with our native species.  It is easily recognized by its triangular shape and by having lateral teeth on both sides of its true cardinal teeth.

See the Mussel Bed for more information on the species in Kansas.



Full-grown Corbicula shells
photo by Jim Mason



IN KANSAS - An informal group made up of federal, state and local government employees, academic researchers, representatives from conservation organizations, teachers and private individuals meets once a year for a workshop on freshwater mussels.  The group publishes The Kansas Pearly Mussel Newsline.  You can download back issues by clicking on the icons below.  The files are in pdf format, which requires Acrobat Reader.
(On a Windows system, download the file by right clicking on the link and choose "Save Target As" to save it to your hard drive, then open it from there.   You will need Acrobat Reader to view this file.  If you don't have that software already, you can get it for free from Adobe.)

bullet1996 issue Click here to download the file (163K)
bullet1997 issue Click here to download the file (220K)
bullet1998 issue Click here to download the file (114K)
bullet1999 issue Click here to download the file (202K)
bullet2000 issue Click here to download the file (213K)
bullet2001 issue Click here to download the file (530K)
bullet2002 issue Click here to download the file (463K)
bullet2004 issue Click here to download the file (212K)
(there was no 2003 issue)



There are 48 species of mussels recorded from Kansas.  Click on the species name in the list below to see detailed range maps, habitat and life history information for each.  The list is based on "A Pocket Guide to Freshwater Mussels", 2008, Great Plains Nature Center, by Edwin Miller, Karen Couch & Jim Mason.  It may be picked up for free at the Great Plains Nature Center or ordered through the mail for a nominal fee.

bulletSpecies portrait web pages have been done for Washboard, Western Fanshell, White Heelsplitter, Pistolgrip and Floater.
bulletThe unionid species on the Kansas Threatened and Endangered Species list are also described in the Kansas Wildlife Refuge.

= Species that are extirpated from Kansas (8).
!! = Species that are endangered in Kansas (7).
= Species that are threatened in Kansas (4).
+ = Species that are in need of conservation in Kansas (11).
NR= Species that are recently recorded and have not been classified. (1)

Sub-Family Cumberlandinae
    Genus Cumberlandia
Spectaclecase - Cumberlandia monodonta
Sub-Family Ambleminae
    Genus Megalonaias
Washboard - Megalonais nervosa
    Genus Tritogonia
           Pistolgrip - Tritogonia verrucosa
    Genus Quadrula
          X Winged Mapleleaf - Quadrula fragosa
          Mapleleaf - Quadrula quadrula
          Pimpleback - Quadrula pustulosa
         + Wartyback - Quadrula nodulata
          Monkeyface - Quadrula metanevra
       !!  Rabbitsfoot - Quadrula cylindrica
    Genus Amblema
           Threeridge - Amblema plicata
    Genus Fusconaia
          + Wabash Pigtoe - Fusconaia flava
    Genus Cyclonaias
         NR Purple Wartyback - Cyclonaias tuberculata
    Genus Pleurobema
            X Pyramid Pigtoe - Pleurobema rubrum
          + Round Pigtoe - Pleurobema sintoxia
    Genus Elliptio
          + Spike - Elliptio dilatata
    Genus Uniomerus
           Pondhorn - Uniomerus tetralasmus

Sub-Family Anodontinae
    Genus Utterbackia
           Paper Pondshell - Utterbackia imbecillis
    Genus Anodonta
Flat Floater - Anodonta suborbiculata
    Genus Pyganodon
           Floater - Pyganodon grandis
      Genus Anodontoides
       + Cylindrical Papershell - Anodontoides ferussacianus
    Genus Strophitus
Creeper - Strophitus undulatus
    Genus Alasmidonta
Elktoe - Alasmidonta marginata
Slippershell - Alasmidonta viridis
    Genus Arcidens
          ! Rock Pocketbook - Arcidens confragosus
    Genus Lasmigona
          X Creek Heelsplitter - Lasmigona compressa
           ! Flutedshell - Lasmigona costata
           White Heelsplitter - Lasmigona complanata

Sub-Family Lampsilinae
    Genus Ptychobranchus
         ! Ouachita Kidneyshell - Ptychobranchus occidentalis
    Genus Obliquaria
          Threehorn Wartyback - Obliquaria reflexa
    Genus Cyprogenia
Western Fanshell - Cyprogenia aberti
    Genus Actinonaias
Mucket - Actinonaias ligamentina
    Genus Ellipsaria
         ! Butterfly - Ellipsaria lineolata
    Genus Obovaria
      X Hickorynut - Obovaria olivaria
    Genus Truncilla
          + Deertoe - Truncilla truncata
         + Fawnsfoot - Truncilla donaciformis
    Genus Leptodea
          Fragile Papershell - Leptodea fragilis
    Genus Potamilus
          Pink Papershell - Potamilus ohiensis
          Pink Heelsplitter - Potamilus alatus
          Bleufer - Potamilus purpuratus
    Genus Toxolasma
          Lilliput - Toxolasma parvus
    Genus Ligumia
Black Sandshell - Ligumia recta
           Pondmussel - Ligumia subrostrata
    Genus Venustaconcha
Ellipse- Venustaconcha ellipsiformis
    Genus Lampsilis
         + Yellow Sandshell - Lampsilis teres
         + Fatmucket - Lampsilis siliquoidea
       !! Neosho Mucket - Lampsilis rafinesqueana
           Plain Pocketbook - Lampsilis cardium
    Genus Epioblasma
Snuffbox - Epioblasma triquetra



Here are some good web sites for mussels in the central part of North America:

bulletDr. Chris Barnhart at Southwest Missouri State University at Springfield has done a tremendous amount of work on breeding mechanisms in unionids.  You can see photos and videos on his web site: http://unionid.missouristate.edu/
bulletKaren Couch has produced a beautiful, hand-illustrated book on the unionids of Kansas. 
Her web site is: http://www.kansasmussels.com/
bulletThe Aquatic Mollusks of North Dakota (photos and range maps) is available on the excellent
Northern Prairie Wildlife Research Center web site.
bulletThe outstanding book "Field Guide to Freshwater Mussels of the Midwest" may be found on the web at the Illinois Natural History Survey web site.
bulletChristine O'Brien and Buddy Tignor have created a fun mussel web site for teachers.

The Freshwater Mollusk Conservation Society is working to raise awareness of, support research on and advocate conservation of freshwater mussels.   Here is their website.

A classic reference for Kansas mussels is "Handbook of Unionid Mussels in Kansas", 1962, Kansas University Museum of Natural History Miscellaneous Publication # 28, by Harold Murray and A. Byron Leonard.   This book is out of print but it's well worth having if you can find a used copy.

In 2008, the Great Plains Nature Center published "A Pocket Guide to Kansas Freshwater Mussels", which covers all the species found in the state.  You can read it online in The Mussel Bed.  Find out how to get a copy here.

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