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Genus Strophitus

Family Unionidae



Strophitus undulatus remains a common to abundant species in most of the metro area and throughout its range. However, in New Jersey it is designated a species of special concern. It occurs from Nova Scotia to Georgia on the Atlantic slope, and west to Saskatchewan and Texas, thriving in small, slow-moving water as well as larger rivers and lakes. S. undulatus is the only species of Strophitus occurring in the Atlantic region.

Species Summary

Species Summary

Strophitus undulatus (Say, 1817)



size: 100mm
beak: typically sharply defined, with coarse concentric sculpture slightly depressed
color patterns: fine green color rays may be apparent on posterior slope; periostracum yellowish or greenish, dark brown; nacre bicolored, white to bluish
shape: sub-ovate to sub-elliptical with posterior end blunt
shell features: shape variable; if beak sculpture is unclear, identification may be difficult
teeth: hinge teeth absent; pseudocardinals may be represented by a slight thickening of the nacre in each valve


abundance: common to abundant
status: US, NY, CT: not legally protected; NJ: special concern
conservation challenges: all freshwater mussels should be carefully monitored, and known locations surveyed on a regular basis to detect possible habitat degradation or  population declines; additional populations of Strophitus and other mussels should be actively sought


N.A. distribution: Nova Scotia (Canada) west to Saskatchewan, south to Pennsylvania and the Atlantic slope to Georgia; and from Ontario southwest through the Ohio and Mississippi River interior basin drainages to Texas
present metro distribution: NY: all watersheds; NJ: lower Hudson River watershed, upper Delaware River watershed; CT: Housatonic River watershed
other regional localities: NY: Lake Ontario watershed, upper Hudson River watershed; NJ: upper Hudson River watershed; CT: Connecticut, Housatonic and Thames River watersheds
historical localities: CT: lower Connecticut River watershed, South central coast watershed


Life History:

habitat: slow water of all sizes, and lakes; substrate: silt, sand, gravel and mixes Habitat Photo
hosts: Ambloplites rupestris (Rafinesque, 1817) rock bass; Ameiurus melas (Rafinesque, 1820) black bullhead; Ameiurus natalis (Lesueur, 1819) yellow bullhead; Campostoma anomalum (Rafinesque, 1820) stoneroller; Cottus cognatus (Richardson, 1836) slimy sculpin; Cubea inconstans (Kirtland, 1841) brook stickleback; Etheostoma caeruleum (Storer, 1845) rainbow darter; Etheostoma exile (Girard, 1859) Iowa darter; Etheostoma flabellare (Rafinesque, 1819) fantail darter; Etheostoma nigrum (Rafinesque, 1820) Johnny darter; Etheostoma olmstedi (Storer, 1842) tessellated darter; Fundulus zebrinus (Jordan and Gilbert, 1883) plains killifish; Ictaluns punctatus (Rafinesque, 1818) channel catfish; Lepomis cyanellus (Rafinesque, 1819) green sunfish; Lepomis gibbosus (Linnaeus, 1758) pumpkinseed; Lepomis macrochirus (Rafinesque, 1819) bluegill; Lota lota (Linnaeus, 1758) burbat; Luxilis cornutus (Mitchill, 1817) common shiner; Micropterus dolomica (Lacepede, 1802) smallmouth bass; Micropterus salmoides (Lacepede, 1802) largemouth bass; Nocomis micropogon (Cope, 1865) river chub; Notophthalmus vidridescens (Rafinesque, 1820) red-spotted newt; Notropis hudsonius (Clinton, 1824) spottail shiner; Notropis lundibundis (Girard, 1856) sand shiner; Oncorhynchus mykiss (Waldbaum, 1792) rainbow trout; Perca flavescens (Mitchill, 1814) yellow perch; Percina caprodes (Rafinesque, 1818) log perch; Percina maculata (Girard, 1859) blackside darter; Percina phoxocephala (Nelson, 1876) slenderhead darter; Pimephales notatus (Rafinesque, 1820) bluntnose minnow; Pimephales promelas (Rafinesque, 1820) fathead minnow; Pomoxis annularis (Rafinesque, 1818) white crappie; Pomoxis nigromaculatus (Lesueur, 1829) black crappie; Rhinichthys atratulus (Hermann, 1804) blacknose dace; Rhinichthys cartaractae (Valenciennes, 1842) longnose dace; Salvelinus fontinalis (Mitchill, 1814) brook charr; Semotilus atromaculatus (Mitchill, 1818) cheek chub; Stizostedion vitreum (Mitchill, 1818) walleye; Umbra limi (Kirtland, 1840) central mudminnow; also, no host required


S. undulatus

Left valve

left valve

Right valve

right valve

Dorsal view

dorsal view

Profile view

profile view


interior profile; bicolored nacre


teeth appear absent

Beak sculpture

beak sculpture coarse, concentric


pseudocardinals appear vestigial

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