MIlUliSnSoEiLs S orth America’s tremendous richness of pearly freshwater mussels is unique. Numbered profile drawings, grouped as COMMERCIAL SPECIES THREATENED/ENDANGERED SPECIES This poster was made possible by: Kspeeciymens are shown above, correspond to 1. Amblema plicata , threeridge 16. Cyclonaias tuberculata , purple wartyback NBiologists have identified nearly 300 species of mussels living in our streams numbered species names. Mussels are not shown 2. Fusconaia flava , Wabash pigtoe 17. Cyprogenia stegaria , fanshell 18. Ellipsaria lineolata , butterfly in equal proportion to actual size. Photographs 3. Megalonaias nervosa , washboard Illinois Department of and lakes. Freshwater mussels are bivalved mollusks with two hard outer shells 19. Elliptio dilatata , spike by Kevin S. Cummings; except Ptychobranchus 4. Quadrula quadrula , mapleleaf 20. Epioblasma triquetra , snuffbox Natural Resources and soft tissues inside. Prehistoric American Indians ate the soft tissues and used fasciolaris by Robert E. Warren. 21. Lampsilis fasciola , wavy-rayed lampmussel Division of Education COMMON SPECIES 22. Plethobasus cyphyus , sheepnose the lustrous shells for making tools and ornaments. Historically, the shells have 1 Illinois State Museum 2 3 5. Lampsilis cardium , plain pocketbook 23. Pleurobema clava , clubshell been prized as raw material for manufacturing buttons and are currently used in 6. Obliquaria reflexa , threehorn wartyback 24. Ptychobranchus fasciolaris , kidneyshell 4 8 25. Quadrula cylindrica , rabbitsfoot 5 6 7 7. Quadrula pustulosa , pimpleback the production of cultured pearls. 26. Villosa iris, rainbow 8. Truncilla donaciformis, fawnsfoot 9 10 11 12 13 9. Truncilla truncata , deertoe EXTINCT SPECIES 27. Epioblasma flexuosa , leafshell Many mussels are sensitive to changes in their environment. Populations of mus - 10. Utterbackia imbecillis , paper pondshell 14 28. Epioblasma personata , round combshell Illinois Department 15 16 sels have declined alarmingly in recent decades because of siltation , pollution, and 17 18 29. Epioblasma propinqua , Tennessee riffleshell of Transportation UNCOMMON/RARE SPECIES competition from exotic mollusks like the zebra mussel. Of the 80 mussel species 20 30. Epioblasma torulosa, tubercled blossom 19 21 22 11. Alasmidonta marginata , elktoe 23 INTRODUCED * SPECIES native to Illinois, more than half are currently threatened , endangered , extirpat - 12. Lampsilis teres , yellow sandshell 25 31. Dreissena polymorpha , zebra mussels (attached Text: Robert E. Warren, Illinois State Museum 24 ed , or extinct . We can protect mussels and other aquatic wildlife by cleaning up 26 27 13. Quadrula metanevra , monkeyface to Potamilus alatus , pink heelsplitter) Kevin S. Cummings, Illinois Natural History Survey 29 14. Tritogonia verrucosa , pistolgrip 32. Corbicula fluminea , Asian clam our streams and lakes to create healthy habitats where these animals can thrive. 28 31 30 32 15. Venustaconcha ellipsiformis , ellipse *See glossar y. Design: Illinois State Museum Freshwater mussels are mem - Freshwater mussels have an Freshwater mussels are commercial - bers of the Phylum Mollusca, elaborate reproductive sys - ly important. Beginning in 1891, Class Bivalvia, and Order tem. This system not only mussels were harvested to manufac - Unionoida. They have a soft provides a way for mussels to ture shell buttons for clothing. inner body and hard outer generate offspring; it also Many towns along the Mississippi shells consisting of two valves, helps each species increase its and Illinois rivers had button facto - one on the left side and one range. Mussels generally have ries or buying stations where mus - on the right side. The shells separate sexes (male and selors sold their shells. The shell- are joined by an elastic liga - female). However, some mus - button industry thrived until the ment that stretches across a sels are hermaphrodites , in 1940s, when plastic replaced shell hinge at the top (dorsal mar - which each individual has as the preferred raw material for buttons. In the early days, no one attempted to gin). The shells of different both male and female repro - manage or control the mussel harvest, and many of the mussel “beds” were severely species vary in size, shape, ductive organs in its body. depleted or destroyed. thickness, color, and in the During spawning , males presence or absence of sculp - release sperm into the water. Mussel harvesting resumed in the 1960s to provide the shell implant or “nucleus” for turing (ridges or bumps) on The sperm are drawn inside a producing cultured pearls. Harvesting continues in the Mississippi River and some of the outer surface. The struc - female’s shell, where they fertilize eggs in her body. The fertilized eggs develop into its tributaries. Over seven-million pounds of mussels, valued at more than six-million ture of the hinge also differs. larvae (glochidia ) and are stored for a time in the female’s gills. When the glochidia dollars, were harvested in 1990. No one knows if mussels can survive at current harvest - Some species have interlock - mature, the female generally expels them into the water where they must attach them - ing rates. Several states in the Midwest are developing new, uniform harvest regulations ing “teeth” ( pseudocardinal selves as parasites to the gills or fins of fishes. In some species, part of the female’s man - to better manage this important natural resource. and lateral teeth) that ensure tle resembles a swimming minnow that lures potential host fish and increases the proper alignment of the chance that her larvae will attach to a suitable fish and survive. Larvae remain on the valves. In other species the hinge teeth are reduced or absent. host fish for a period of weeks or months. During this time the larvae metamorphose ILLUSTRATIONS and develop adult organs and structures. Young mussels then detach from their hosts Above: “Mussel fishing on the Illinois River, Pearl, ILL.” (photo courtesy of Marshall Mussels’ soft tissues include an enveloping mantle that secretes the shell, a single and drop to the bottom of the body of water. Thanks to the swimming fish, they may County Historical Society). large foot for moving short distances, and adductor muscles for keeping the valves now be far away from their parents. Below left: Drilled yellow sandshell mussel ( Lampsilis teres ) and button blanks, and tightly closed. Mussels also have two pairs of multipurpose gills. The gills are used buttons (photo by R. E. Warren, Illinois State Museum). for respiration, for moving microscopic food particles to the animal’s mouth, and Mature mussels spend most of their lives, which range from 10 to 100 years, partially Below right: Cultured pearl necklace (photo by R. E. Warren, Illinois State also for housing and nourishing mussel larvae (glochidia ) in females. or wholly buried in the bottoms of streams and lakes. Mussels often have specialized Museum). habitat preferences. Many species cannot live in muddy streams with excess amounts ILLUSTRATIONS of silt. Above: Medial and lateral views of a mapleleaf mussel ILLUSTRATIONS (Quadrula quadrula ) Above: Generalized life cycle of showing the anatomical freshwater mussels (from features of the shell (from Cummings and Mayer 1992: 2). Cummings and Mayer Right: Mantle-flap lure of pocket - 1992: 7). book mussel ( Lampsilis ovata ; from Right: Soft-tissue anatomy Stolzenburg 1992:21; photo by (from Burch 1973: 7). Richard J. Neves). Historically, Illinois had as many as 80 mussel species in its rich network of streams and bivalve mollusk with a shell made of two hinged valves lakes. However, recent stream surveys in Illinois and throughout the United States have documented drastic declines in channelization the straightening and/or deepening of a river channel mussel populations. Today mussels endangered a species faced with the danger of extinction may be the most endangered group of animals in North America. Of extinct a species that no longer exists the 80 species that once lived in Illinois waters, only 59 have been extirpated a species that has been eliminated from a particular area found in the state since 1970. but still exists somewhere else Eleven of the remaining 59 species are now known from only a single exotic from another part of the world; foreign river system or population, and glochidium the larva of a freshwater mussel (Superfamily Unionoidea) they may disappear by the end of that generally lives as a temporary parasite on a host fish the next decade. Illinois hermaphrodite an animal or plant normally having both male and Many factors are responsible for the female reproductive organs decline of freshwater mussels, including siltation , pollution, loss introduced brought in and established in a new place or surroundings of habitat, channelization of streams, and competition from larva the newly hatched, immature form of an animal that exotic species like the zebra mussel undergoes metamorphosis , differing markedly in form (Dreissena polymorpha ). or appearance from the adult ILLUSTRATIONS metamorphosis a marked change in the form or structure of an animal Above: Bar chart of percent occurring after birth or hatching (vt. metamorphose ) decline of species diversity in mollusk soft-bodied animal with a muscular head and foot and a selected Illinois streams (data from Illinois Natural History Survey). mantle, which usually secretes a protective shell Right: Base map of streams in parasite an organism that grows, feeds, and is sheltered on or in Illinois