New York Natural Heritage Program
Eastern Pearlshell
Margaritifera margaritifera (Linnaeus, 1758)
Bivalves

General Description [-]
The Eastern Pearlshell has a thick subelliptical, elongate shell which is arched and is up to 150 mm long. The beak sculpture is coarse and concentric. The periostracum is dark brown to black, without rays. The pseudocardinals are strong, but laterals nearly to entirely absent. The nacre is pearly white, sometimes with pink to purplish coloration (Strayer and Jirka 1997).

Identifying Characteristics [-]
The Eastern Pearlshell is the only member of the family Margaritiferidae in the state, and its biology and distribution are unique among Unionoids in New York.

Characters Most Useful for Identification [-]
The shell has a blackish, rayless periostracum and conspicuous pores on the shell interior (Strayer and Jirka 1997).

Best Life Stage for Proper Identification [-]
Adult.

Behavior [-]
Adults of this species are sessile, with only limited movement in the substrate. Passive downstream movement may occur when they are displaced from the substrate during floods. More major dispersal occurs while glochidia are encysted on their Salmonid hosts. Being ectothermic, mussels presumably have reduced activity levels during colder months of the year. The Eastern pearlshell is thought to be the longest-lived invertebrate animal; the maximum lifespan was observed to be 132 years and the mean age of sexual maturity is 20 years (Bauer 1992). This species has a very high fecundity (upward of 17 million glochidia produced annually) and the smallest glochidia (Bauer 1987).

Diet [-]
Adult mussels are filter feeders. Algae, detritus, and bacteria are all important food sources. Mussels in turn are eaten by muskrats, raccoons, fish, and birds. Several different Salmonid fishes including Brook and Brown Trout serve as glochidial (larval) hosts (Strayer and Jirka 1997).
Eastern Pearlshell Images
click to enlarge
The Best Time to See
Little is known about the activity periods of Unionoid mussels but they are presumed to be greatly reduced during cold times of the year. Freshwater mussels are most often easiest to locate during late summer when water levels are lowest.
J F M A M J J A S O N D
Present Reproducing
The time of year you would expect to find Eastern Pearlshell present (blue shading) and reproducing (orange shading) in New York.
Similar Species
  • Eastern Elliptio (Elliptio complanata)
    The shell of E. complanata is not arched, has a mostly brownish periostracum, with well developed lateral teeth and fine color rays.