Missouri Department of Conservation
Missouri Department of Conservation

Taxonomy

Common Name: ELEPHANTEAR

Phylum: MOLLUSCA

Class: BIVALVIA

Order: UNIONOIDA

Family: UNIONIDAE

Genus: ELLIPTIO

Species: CRASSIDENS

Taxonomic Authority: (LAMARCK)

Taxonomy References: 015 , 001

Status

STATE ENDANGERED
STATE RANK S1
GLOBAL RANK G5

Status References: 002 , 004

Habitat Summary

"Found in creeks to large rivers in substrates of fine gravel to cobble/boulder."

Primary Habitat: "Aquatic - river/stream"

References: 013 , 003 , 008 , 009 , 010

Distribution

General Occurrence in State:

"Has been found in the Mississippi River and Meramec, Osage, Little Black and Castor River drainages *003,004*"

County Occurance

County Occurence
Known Likely Unknown Not Likely Historic Extirpated
BOLLINGER ADAIR CEDAR
BUTLER ANDREW CLARK
COLE ATCHISON JEFFERSON
CRAWFORD AUDRAIN MARION
FRANKLIN BARRY
GASCONADE BARTON
MARIES BATES
MILLER BENTON
OSAGE BOONE
POLK BUCHANAN
PULASKI CALDWELL
RIPLEY CALLAWAY
ST. CHARLES CAMDEN
ST. LOUIS CAPE GIRARDEAU
WAYNE CARROLL
WRIGHT CARTER
CASS
CHARITON
CHRISTIAN
CLAY
CLINTON
COOPER
DADE
DALLAS
DAVIESS
DEKALB
DENT
DOUGLAS
DUNKLIN
GENTRY
GREENE
GRUNDY
HARRISON
HENRY
HICKORY
HOLT
HOWARD
HOWELL
IRON
JACKSON
JASPER
JOHNSON
KNOX
LACLEDE
LAFAYETTE
LAWRENCE
LEWIS
LINCOLN
LINN
LIVINGSTON
MACON
MADISON
MCDONALD
MERCER
MISSISSIPPI
MONITEAU
MONROE
MONTGOMERY
MORGAN
NEW MADRID
NEWTON
NODAWAY
OREGON
OZARK
PEMISCOT
PERRY
PETTIS
PHELPS
PIKE
PLATTE
PUTNAM
RALLS
RANDOLPH
RAY
REYNOLDS
SALINE
SCHUYLER
SCOTLAND
SCOTT
SHANNON
SHELBY
ST. CLAIR
ST. FRANCOIS
STE. GENEVIEVE
STODDARD
STONE
SULLIVAN
TANEY
TEXAS
VERNON
WARREN
WASHINGTON
WEBSTER
WORTH

References for distribution: 013 , 003 , 004 , 008 , 009 , 010

Distribution by Watersheds

Meramec R.
Castor R. and Castor R. Diversion Channel
Osage R. from Bagnell Dam to Mo. R.
Gasconade R. from Headwaters to Big Piney R.
Gasconade R. from Big Piney R. to Mo. R.
Black R.
Current R.

Comments: "Dead shells have been found in unit 07110009 (St. Charles county, 1998) but no living specimens have been found there *004*."

Distribution by Ecoregions

Mississippi River Alluvial Plains, Ozark Highlands

Comments: ""

Distribution by Potential Natural Vegetation

Oak-Hickory Forest
Oak-Hickory-Pine Forest

Distribution by Natural Divisions of Missouri

Ozark Border: Missouri River
Ozark Border: Mississippi River
Ozark: Upper Ozark
Ozark: Lower Ozark
Mississippi Lowlands: Lowlands

Habitat Associations

Species is associated with "Aquatic" habitats.

National Wetlands Inventory Association:

Riverine

Aquatic Associations:

"Riverine, lower perennial", "Unconsolidated bottom, cobble/gravel",
"Riverine, lower perennial", "Unconsolidated bottom, sand",

References for Aquatic Associations: 013 , 003 , 008 , 009 , 010

Habitat Types:

Permanent Stream

References for Habitat Types: 013 , 003 , 008 , 009 , 010

Terrestrial Natural Communities:

References for Terrestrial Natural Communities:

Food Habits

Trophic Level:

"Omnivore"

Larval Food Habits

Comments for larval food habits:
""

References for larval food habits:

Juvenile Food Habits

Comments for Juvenile Food Habits:
""

References Juvenile Food Habits

Adult Food Habits

Algae; Not Specified
Protozoans; Not Specified
Other Microorganisms; Not Specified
Bacillariophyceae (diatoms); Not Specified

Comments for Adult Food Habits:
""

References Adult Food Habits 011

Niche Requirements

Egg Niche Requirements

References for egg niches requirements:

Feeding Larvae Niche Requirements

References for feeding larvae niche requirements:

Resting Larvae Niche Requirements

References for resting Larvae niche requirements:

Feeding Juvenile Niche Requirements

References for feeding juvenile niche requirements:

Resting Juvenile Niche Requirements

References for resting juvenile niche requirements:

Breeding Adult Niche Requirements

References for feeding Adult niche requirements:

Feeding Adult Niche Requirements

References for feeding adult niche requirements:

Resting Adult Niche Requirements

References for resting adult niche requirements:

Niche Requirement Summary

Current velocity specified in comments(00150)
Elevation specified in comments(00240)
Gradient specified in comments(00140)
Host specified in comments(00680)
Substrate specified in comments(00080)
Water depth specified in comments(00230)

Comments about Life History:

Code Comment
007 Reproductive period is June to July *05*.
003 Fish host for glochidia is the skipjack herring *06*.
020 Eggs are fertilized and develop into glochidia in gills of female *03*.
034 Limited by availability of suitable habitat and presence of host species *03*.
035 Regulatory factors include predation *03*.
037 Depend on host for dispersal *03*.

Life History Information

Limiting factors specified in comments(034)
Regulatory factors specified in comments(035)
Dispersal specified in comments(037)
Origin in state: native
Seasonal distribution in state: all seasons
Closely associated plant or animal species specified in comments(003)
Foraging strategy: filtering
Foraging sites: water
Breeding season specified in comments(007)
Duration of pair bond: no pair bond formed
Development of young at birth/hatching specified in comments(020)

Comments about Life History:

Code Comment
007 Reproductive period is June to July *05*.
003 Fish host for glochidia is the skipjack herring *06*.
020 Eggs are fertilized and develop into glochidia in gills of female *03*.
034 Limited by availability of suitable habitat and presence of host species *03*.
035 Regulatory factors include predation *03*.
037 Depend on host for dispersal *03*.

References for life history: 013 , 003 , 005 , 006 , 007

Management

Beneficial Management Practices:

Water - control sedimentation
Water - control pollution (thermal, physical, chemical)
Water - control pollution (thermal, physical, chemical)
Water - stabilize streambanks
Water - other (specify in comments)
Forest - maintain streambanks
Forest - maintain streamside vegetation

Beneficial Management References: 013 , 014

Adverse Managment Practices:

Water - application of herbicides
Water - application of pesticides
Water - application of insecticides
Water - dredging and filling
Water - navigational improvements (channelization, dams, locks)
Water - gravel dredging in streams

Adverse Management References: 013 , 014

Comments on Management:
No work should be allowed below the high bank of the stream between May 1 and July 31, to allow for successful reproduction and recruitment. Take precautions to prevent spread of zebra mussels *013*. The construction of Lock and Dam 19 in the upper Mississppi River inhibits E. crassidens from recolonizing the Mississippi above the dam by preventing its migratory host fish from moving upstream. Conservation efforts should focus on artificial propagation and dam modifications that allow the passage of migratory fishes *014*.

References for Management Comments: 013 , 014

References

Reference Code Citation
001 Williams, J.D., A.E. Bogan, R.S. Butler, K.S. Cummings, J.T. Garner, J.L. Harris, N.A. Johnson and G.T. Watters. 2017. A revised list of the freshwater mussels (Mollusca: Bivalvia: Unionida) of the United States and Canada. Freshwater Mollusk Biology and Conservation 20:33-58.
002 Missouri Natural Heritage Program. 2004. Missouri Species and Communities of Conservation Concern Checklist. Missouri Department Of Conservation. Jefferson City, Missouri. 47 Pp.
003 Oesch, R.D. 1995. Missouri Naiades. A Guide To The Mussels Of Missouri. Second Edition. Missouri Dept. Of Conservation. Jefferson City, Missouri. 271 Pp.
004 Unpb Missouri Department of Conservation Heritage Database. P.O. Box 180, Jefferson City, Mo 65102.
005 Baker, F.C. 1928. The fresh-water mollusca of Wisconsin. Part II. Pelecypoda. Bull. Univ. Wisconsin, Bull. 70, II. WI Geol. and Nat. Hist. Surv. Gen. Ser. 1301, 495 pp. (cited in ref. 001)
006 Fuller, S.L.H. 1978. Fresh-water mussels (Mollusca: Bivalvia: Unionidae) of the Upper Mississippi River: Observations at selected sites within the 9-foot channel navigation project on behalf of the Unites States Army Corps of Engineers. Acad. Nat. Sciences. Philadelphia, PA. 401 pp. (cited in ref. 003).
007 Brynildson, I. 1985. Freshwater mussels of the Upper Mississippi River. Wisc. Dept. Nat. Resources. 63 pp.
008 Buchanan, A. C. 1980. Mussels (naiades) of the Meramec River Basin. Missouri Dept. of Conservation Aquatic Ser. No. 17. Jefferson City, MO. 76 pp.
009 Unpb Grace, T.B. and A.C. Buchanan. 1981. Naiades (Mussels) Of The Lower Osage River, Tavern Creek, And Maries River, Missouri. Mo Dept Of Conservation, 1110 S. College Ave., Columbia, Mo 65201 (573-882-9880). 147pp.
010 Unpb Bruenderman, S. Mussel Occurrence Database. Missouri Dept. Of Conservation, 1110 S. College Ave., Columbia, Mo 65201 (573-882-9880).
011 Allen, W.R. 1914. The Food And Feeding Habits Of Freshwater Mussels. Biol. Bull. 27(3):127-139.
013 Missouri Department of Conservation. Best Management Practices: Elephant-ear mussel. Missouri Dept. of Conservation. Jefferson City, MO.
014 Kelner, D.E. and B.E. Stietman. 2000. Relic populations of the Ebony Shell, Fusconaia ebena (Bivalva: Unionidae), in the Upper Mississippi River Drainage. Journal of Freshwater Ecology 15(3): 371-377.
015 Freshwater Mollusk Conservation Society (FMCS). 2021. The 2021 checklist of freshwater mussels. https://molluskconservation.org/Library/Committees/Names/Appendix_1_Bivalves_Revised_Names_List_20210825.pdf.