What are Mussels?
Freshwater mussels (Mollusca: Unionacea) are a fascinating group of animals that reside in our streams and lakes. They are frontline indicators of environmental quality and have ecological ties with fish to complete their life cycle and colonize new habitats. As filter-feeders, they can help improve both water quality and clarity, and they are an important part of the aquatic food web. Please do not confuse our native mussels with two exotic nuisance or “weed” species that have spread into Kansas, the Asiatic clam and zebra mussel.
Kansas is the home of 40 living species of native freshwater mussels. Another 8 species were here in the past but are no longer found in our rivers, streams and lakes (see extirpated species). Over half of the extant species are listed as threatened (T), endangered (E) or species-in-need-ofconservation (SINC). This is not surprising, because freshwater mussels have been identified as one of the most imperiled groups of animals in North America. The major threats to mussels are pollution, dewatering of streams, stream channelization and dams. Improvements in water quality through the diligent prevention of point and nonpoint source pollution, combined with adequate flow, are essential to help these unique invertebrates continue to make our rivers, streams and lakes their home in the future.
The purpose of the Mussel Bed is to show the diversity, range and beauty of freshwater mussels in Kansas. It is hoped once your interest is piqued, other sources of information will be sought to learn more about these mollusks. Some useful references are listed below. The range maps are based on museum collection vouchers, Kansas Department of Health and Environment sampling data and Kansas Department of Wildlife, Parks & Tourism stream surveys. See the glossary for help with the unique terminology used to describe the anatomy and life history of these animals..
The Mussel Bed has information on all 48 species of Unionid mussels recorded in Kansas, as well as two invasive species of non-unionid bivalve mollusks. Click on the links to learn more about each of them.
T = Threatened E = Endangered SINC = Species in need of Conservation
* = Non-native X = Extirpated from Kansas
(Otherwise a species is common within it's range)
The mussels of this group have very minimal hinge teeth as adults or none at all. The glochidia possess a pair of hooks that enable them to clamp onto external features of host fish such as fins and scales.
Elktoe - E
Flat Floater - E
Cylindrical Papershell - SINC
Rock Pocketbook - T
Flutedshell - T
Creeper - SINC
All members of this group have very thick shells with well-developed hinge teeth. The glochidia all lack hooks and therefore encyst on the gills of the host fish. Several species produce conglutinates (worm-like lures) that are released into the water column. These often mimic food items fish prefer. For this reason most have a large array of suitable fish hosts.
Purple Wartyback - rarely found in the lower Marais des Cygnes River
Spike - SINC
Wabash Pigtoe - SINC
Washboard - SINC
Round Pigtoe - SINC
Rabbitsfoot - E
Wartyback - SINC
The mussels within this subfamily often have shells that are sexually dimorphic (males and females are visibly different). Female shells are typically inflated. This provides more room for the females to brood her many young within her gill pouches. The glochidia from this group are all gill parasites. The females often have a developed visual lure as part of their mantle tissue that is inflated, extended and moved independently. This mantle tissue often realistically mimics a small baitfish or crayfish. Water clarity is essential for the host fishes to see the lures being displayed by these gravid females.
Mucket - E
Western Fanshell - E
Butterfly - T
Neosho Mucket - E
Fatmucket - SINC
Yellow Sandshell - SINC
Fawnsfoot - SINC
Deertoe - SINC
Ellipse - E
Byssal thread – a fibrous string that anchors a small mussel to a larger object
Extant – population exists in specified area
Extirpated – population is gone from specified area (locally extinct)
Fluting – repeated ridges and valleys alternately arranged
Glochidia – larvae of unionid mussels that have not transformed to juveniles
Hinge – the edge of the shell where the two valves are physically connected
Iridescent – displaying rainbow-like colors that shift with lighting angle
Lateral teeth – the elongate, interlocking ridges on the hinge line of each valve
Mantle – the fleshy tissue that is attached to the nacre and envelops a mussel’s soft parts
Mollusk – an animal group that includes mussels, clams, oysters, snails, squid and octopuses
Nacre – the pearly interior of a mussel shell that may vary in color
Pallial line – the indented groove on the inner shell surface, roughly parallel to the ventral edge, that marks where the mantle was formerly attached
Periostracum – the outermost external layer of a shell
Pseudocardinal teeth – the interlocking tooth-like structures located near the umbo
Pustule – a small bump or knob
Rays – a solid or broken stripe on the periostracum that usually radiates from the umbo
Relic – a dead shell that has weathered
Sculpture – raised portions on the shell exterior that form lines, ridges or pustules
Sulcus – a narrow shallow shell depression extending from umbo to ventral margin
Umbo – the area of the shell first to form (sometimes called the beak)
Valve – one of the halves of a shell
Veliger – free-swimming larva that does not require fish host attachment to mature to juvenile stage
Wing – a thin posterior extension of the shell most notable on heelsplitters
Couch, K. J, 1997
"Unionid Mussels of Kansas", 123 pp.
Available from the author at www.kansasmussels.com
Cross, F. B. and J. T. Collins, 1995.
"Fishes in Kansas. Second Edition, revised", 315 pp.
Available from University Press of Kansas
Cummings, K.S. and C.A. Mayer. 1992.
"Field Guide to Freshwater Mussels of the Midwest"
Illinois Natural History Survey Manual 5. 194 pp.
Print copies available from the Illinois Natural History Survey
Or read it online using the links on the same page.
Murray, Harold and A. Byron Leonard, 1962
"Handbook of Unionid Mussels in Kansas"
Kansas University Museum of Natural History Miscellaneous Publication # 28, 184 pp.
Available for $8.95 from the Owl's Nest Gift Shop at the Great Plains Nature Center.
Oesch, R.D., 1984.
"Missouri naiads: a guide to the mussels of Missouri", 271 pp.
Missouri Department of Conservation
OUT OF PRINT