Illinois The Silent Storytellers by Robert E. Warren, Associate Curator of Anthropology

The Water Nymph or nymph); and a superfamily of freshwater dant in lakes. They also have preferences for A nymph lives under water mussels (Unionoidea; formerly Naiadacea). certain water depths (shallow or deep), cur- in our rivers, in our lakes. Biological terminology has changed rent velocities (swiftly moving or standing It is mute but tells us stories through the years, and today the term na- water), and substrate compositions (coarse of our past, of our mistakes. iad is rarely used as a name for freshwater gravel or fine mud). Given the habitat pref- For it sees what’s in the water mussels. However, the metaphor relating erences of different , when an aquatic and responds accordingly. mussels to the water nymphs of Greek my- environment changes, the species composi- It will thrive or it will flounder, thology still seems appropriate. Mussels have tion of the local community changes adjusting its diversity. no supernatural control over the life and accordingly. When we pollute the water, health of aquatic environments, but they do Mussels play several key roles in the eco- when we let our topsoil go, respond to changes in their environments. system. As filter feeders they help clarify The nymph will keep a record. Old mussel shells provide a record of how water and concentrate impurities in their If we read it, we will know. our rivers and lakes have changed; they tell shells and soft tissues. They also serve as a It has lived here through the ages, the story of aquatic environments, past and food resource for , , the since before the dawn of man. present. Mussel communities have docu- freshwater drum fish, and other aquatic and Can it survive another decade? mented changes in the Illinois River from semi-aquatic . In prehistory, mus- With your help, perhaps it can. prehistoric to modern times. sels were used by Native Americans as both When you look into the water Mussels are invertebrate animals in one a source of food and as a raw material for of the stream flowing to sea, of the most diverse phyla in the king- the manufacture of shell tools, utensils, and Ask yourself: Is this a healthy place dom, the phylum . Other mollusks ornaments. Mussels were also important his- for a water nymph to be? include solenogasters, tuskshells, chitons, torically—as sources of pearls during the late Who is this nymph I speak of? snails, slugs, clams, scallops, squids, and oc- 1800s and in the lucrative shell-button in- It is the naiad Unio. topuses. dustry from 1890 to 1950. A new market A bivalve with a pearly shell, Mussels have soft inner bodies and hard for mussel shell came into being in about has one foot, but no toes. outer shells consisting of two valves, one on 1960. Shells are now being exported to Ja- the left side and one on the right. The shells pan, where they are made into small spheres n Greek mythology, the world was are joined by an elastic ligament that and then implanted into living oysters to inhabited by nymphs of various kinds. stretches across a hinge at the top. The shells create cultured pearls. IThey were feminine divinities of of different species vary in size, shape, thick- Historically, mussels were diverse and nature, often portrayed as beautiful ness, color, and in the presence or absence abundant in the Illinois River. Forty-eight maidens, which dwelled in the mountains, of sculpturing (ridges or bumps) on the species have been documented in it. By forests, meadows, and waters. Each was outer surface of the shell. The morphology 1910 it had become the most productive responsible for giving life and perpetuity of the hinge is also diagnostic; some species stream (per river mile) in the early history to its own domain. The nymphs presiding have interlocking “teeth” that ensure proper of the shelling industry. However, when over lakes, rivers, springs, and fountains alignment of the valves, while in other spe- William C. Starrett of the Illinois Natural were called Naiades (Greek: ;"YU*,H). cies the hinge teeth are reduced or absent. History Survey conducted an extensive sur- Biologists have applied the name “na- Mussels live in a variety of aquatic envi- vey of mussels in the river in 1966, only 23 iad” to several types of plants and animals, ronments, including rivers, creeks, lakes, and species remained. These numbers represent all of which inhabit aquatic environments. ponds. Of interest is the fact that many spe- an alarming 52% decline in species diver- These include a family of aquatic plants cies have specific habitat preferences. Some sity in a span of little more than 50 years. (Naiadaceae); an aquatic larval stage of drag- prefer large rivers, others are found only in In some segments of the river the devasta- onflies, mayflies, and other insects (naïad small streams, and still others are most abun- tion has been especially severe. The upper

THE LIVING MUSEUM • VOLUME 57 • NO. 2 • 1995 19 marked by an extensive bed of shells that Table 1. Freshwater Mussels from the Illinois River runs along the beach and covers a nearby Prehistoric Modern Modern natural levee. Prehistoric artifacts have been mussels mussels status1 found in association with the shells and (Nancy’s (La Grange many of the latter have been discolored by Scientific name Common name Point Site) Pool, 1966) fire. The high incidence of charred shell Subfamily Anodontinae Anodonta suborbiculata Flat floater — 1 l (14%) and the absence of any shell arti- Arcidens confragosus Rock-pocketbook 2 16 l facts suggest that the mussels were collected complanata White heelsplitter — 5 l as a food resource and then discarded as Lasmigona costata Fluted-shell 5 — ¡ garbage. Artifacts dating to the Early Pyganodon grandis Giant floater — 29 l Strophitus undulatus Squawfoot 21 — ¡ Woodland cultural period (2100–2550 Utterbackia imbecillis Paper pondshell — 2 l years ago) occur on the site, although they Subfamily Ambleminae are not necessarily associated with the Amblema plicata Threeridge 147 363 l shells. We do not yet know the shell bed’s crassidens Elephant-ear 24 — ¡ Elliptio dilatata Spike 981 — ¡ antiquity, although we can be certain that Fusconaia ebena Ebonyshell 20 — ¡ it predates the modern era. Fusconaia flava Wabash pigtoe 51 1 l Thirty-three species of mussels are rep- Megalonaias nervosa Washboard 5 23 l resented in the prehistoric and modern col- Pleurobema coccineum Round pigtoe 10 — ¡ Pleurobema rubrum Pyramid pigtoe 17 — ¡ lections (Table 1). The prehistoric collec- Quadrula nodulata Wartyback 2 5 l tion (28 species) is considerably more di- Quadrula pustulosa Pimpleback 20 13 l verse than the modern sample (18 species). Quadrula quadrula Mapleleaf 4 86 l This drop-off in diversity is probably re- Tritogonia verrucosa Pistolgrip 4 — ¡ Subfamily Lampsilinae lated to the recent decline of mussel popu- Actinonaias ligamentina Mucket 63 — ¡ lations during the 20th century. Although Ellipsaria lineolata Butterfly 2 — ¡ 13 species found in the prehistoric collec- Epioblasma triquetra Snuffbox 3 — ¡ tion are still common in the Illinois River, Lampsilis siliquoidea Fatmucket 2 2 l Lampsilis teres Yellow sandshell 1 8 l four species are rare and 11 others have Leptodea fragilis Fragile papershell 2 21 l been eliminated (extirpated) from the river. Ligumia recta Black sandshell 1 — ¡ But which species have been extirpated? Obliquaria reflexa Threehorn wartyback 17 1 l Obovaria olivaria Hickorynut 3 — ¡ Potamilus alatus Pink heelsplitter 10 1 l Potamilus ohiensis Pink papershell — 12 l Toxolasma parvus Lilliput 10 — ¡ Truncilla donaciformis Fawnsfoot 34 — ¡ Truncilla truncata Deertoe 89 2 l

Total 1550 591

1Conservation status in 1966: l = Present in Illinois River; ¡ = Rare or Absent in Illinois River (data from Starrett 1971). portion (above Starved Rock) had a rich difficult to say which causes are most im- mussel fauna in the 1870s, but until very portant, as many interacting factors may be recently, no living mussels had been found involved. there since 1912.1 Unfortunately, the dis- One kind of evidence that deserves at- appearance of mussels in the Illinois River tention is the testimony of the mussels parallels national trends; more than 70% of themselves. In what ways have mussel com- North American mussel species are now munities changed? Also, can we learn any- considered endangered, threatened, or of thing by comparing the habitat preferences special concern. of modern communities with communities Why are they dying? We have altered our that lived in the past? rivers and lakes so extensively—through pol- William Starrett’s survey provides good lution, siltation, and commercial develop- information on the modern composition of ment—that many species can no longer sur- mussel communities in the central Illinois vive in places where they once thrived. It is River (the La Grange Pool). Collections of old shells from archaeological and geologi- 1. The long absence of mussels in the upper section of the river may have been part of a massive, cal sites provide useful data on earlier com- progressive mussel die-off caused by the diversion munities. One such collection is that recov- Prehistoric freshwater mussels from the Nancy’s Point site, of untreated Chicago sewage and industrial wastes ered from the Nancy’s Point site, a prehis- length = 94 mm); Lower, threeridge mussel (Amblema into the Des Plaines and Illinois rivers after the toric occupation located on the west bank opening of the Chicago Sanitary and Ship Canal the most abundant species at Nancy’s Point, but they no in 1900. of the river in Fulton County. The site is tolerant of pollution and silt, and are the most abundant

20 THE LIVING MUSEUM • VOLUME 57 • NO. 2 • 1995 body types, water depths, current velocities, and substrate types and it produces general “habitat scores” for the collections analyzed. The habitat scores derived during this analysis reveal major differences between the prehistoric and modern mussel faunas. The prehistoric mussels signify a large river with relatively shallow water, a swift current, and a coarse gravelly substrate. This is the clas- sic signature of a big-river shoal or riffle, in which many mussel species adapted to smaller streams live in the shallow water alongside mussels that live primarily in big rivers. In contrast, the habitat scores of the modern fauna indicate a more specialized big-river mussel community adapted to deeper water, a slower current, and a finer muddy substrate (Table 2). Clearly, significant changes in mussel habitat have occurred along the central Illi- First row (left to right): slippershell mussel (Alasmidonta viridis); rainbow (Villosa iris); nois River. The mussels seem to be telling hickorynut (Obovaria olivaria). Second row (left to right): plain pocketbook (Lampsilis us that they have lost an important habitat cardium); mucket (Actinonaias ligamentina). Shown here 0.60 actual size. Photo by Marlin Roos. type, the big-river shoal, which may have been crucial for the survival of many spe- Just the rare ones that may have disappeared prehistoric abundance spectrum have been cies. What were the main causes of this loss? due to chance or because of minor changes eliminated—the abundant, the common, Two factors are implicated. First, the con- in the river environment? The numbers of and the rare. Two of the four most com- struction of locks and dams along the Illi- identified shells from the Nancy’s Point site mon species in the Nancy’s Point collection nois River has increased water depths and indicate that species from throughout the have disappeared: the spike (Elliptio slowed current velocities. Second, erosion dilatata), which ranks first in abundance from agricultural runoff has deposited mil- (63% of the total), and the mucket lions of tons of silt in our streams. The (Actinonaias ligamentina), which ranks mussels’ message seems to be that by tam- fourth (4% of the total).2 Overall, more than ing our shoals and muddying our waters, three-fourths of the prehistoric shells (77%) we have eliminated an environment where are species rare or absent in the Illinois River many of them once thrived. today. And what of the future? Illinois mussels In comparison, the modern collection are still threatened by pollution, siltation, from the Illinois River is dominated by the impoundments, and other old enemies. But threeridge (Amblema plicata). This species they also face a new threat from their dis- accounts for 61% of the live mussels docu- tant east-European cousins, the zebra mus- mented by Starrett in the La Grange Pool, sels (Dreissena polymorpha). These foreign and it was the most common species in invaders crossed the Atlantic Ocean in ships many of the areas he sampled. Other com- and gained a foothold in the eastern Great mon species include the mapleleaf Lakes about 1987. Since then, the aliens (Quadrula quadrula) and the giant floater have expanded throughout the Great Lakes (Pyganodon grandis). To compare the environmental adapta- tions of the prehistoric and modern mussel Table 2. Changes in Mussel faunas, I analyzed the shells using a com- Faunas Reflect Changes in the puter program that I had previously devel- Central Illinois River Environment oped called UNIO. (Unio is a Latin word meaning “pearl.” It has been used as a ge- Prehistoric Modern nus name for many species of freshwater Habitat mussels1 mussels2 mussels in Europe and North America.) Water-body type Large River Large River UNIO accounts for habitat preferences of Water depth Shallow Deep Illinois. Upper, spike mussel (Elliptio dilatata; right valve; different mussel species in various water- Current velocity Swift Moderate plicata; right valve; length = 91 mm). Spike mussels were Substrate composition Gravelly Muddy 2. Recent collections by the Illinois Natural History longer live in the Illinois River. Threeridge mussels are more Survey indicate the mucket may be making a 1Nancy’s Point site fauna species in the Illinois River today. Photo by Robert Warren. comeback in some sections of the Illinois River. 2La Grange Pool fauna, 1966

THE LIVING MUSEUM • VOLUME 57 • NO. 2 • 1995 21 Additional Reading

Cummings, Kevin S., and Christine A. Mayer. 1992. Field Guide to Freshwater Mussels of the Midwest. Manual 5. Illinois Natural History Survey, Champaign. Starrett, William C. 1971. “A Survey of the Mussels (Unionacea) of the Illinois River: A Polluted Stream.” Illinois Natural History Survey Bulletin 30(5):267–403. Stolzenburg, William. 1992. “The mussels’ message.” Nature Conservancy 42(6): 16–23. Warren, Robert E. 1991. “Freshwater mussels as paleoenvironmental indicators: a quantitative approach to assemblage analysis.” In Beamers, bobwhites, and blue-points: tributes to the career of Paul W. Parmalee, edited by J. R. Purdue, W. E. Klippel, and B. W. Dr. Warren examining some specimens in the ISM’s collections of fresh water mussels at Styles. Scientific Papers Vol. 23. Illinois the Research and Collections Center, Springfield. Photo by Marlin Roos. State Museum, Springfield. Warren, Robert E. 1992. UNIO: A and much of the Mississippi River system. dense colonies on the shells of native mus- Spreadsheet Program for Reconstructing They have become a costly headache for sels, limiting their mobility and robbing Aquatic Environments Based on the swimmers, boaters, municipal utilities, and them of oxygen and food. By the autumn Species Composition of Fresh-Water native aquatic wildlife. of 1994, up to 90% of some native mussel Mussel (Unionoidea) Assemblages. Zebra mussels were first detected in the species had been killed at some locations. Quaternary Studies Program Technical Illinois River in 1991, and by 1993 they Some zebra-mussel populations also crashed Report 92-000-3. Illinois State had attained peak densities of up to 94,000 in 1994, but are expected to rebound be- Museum, Springfield. individuals per square meter. They formed fore they crash again. If the native mussels Warren, Robert E. 1995. “Premodern can survive these dramatic fluctuations, per- Pleurobema rubrum (Rafinesque 1820) haps the zebra mussels will eventually sta- from the Illinois River.” Transactions of bilize at a tolerable level. We can only hope the Illinois State Academy of Science that the next chapter in the water-nymph’s 88(1–2): 5–12. saga is one of conflict and survival, rather than extinction. ❦

Map of the Illinois River, showing the loca- tions of the Nancy’s Point site and the La Invading colony of zebra mussels attached to a native mussel. Zebra mussels pose a new threat to Grange Pool. the survival of native mussel species. Photo by Scott D. Whitney, Illinois Natural History Survey.

22 THE LIVING MUSEUM • VOLUME 57 • NO. 2 • 1995