76
Threeridge, Amblema plicata
Description: The Threeridge has a
medium sized shell that is oval shaped
and very thick. The posterior end will
have three or more rows of large,
parallel, rounded ridges from the beak
to the shell edge. The epidermis is
dark, almost black, in adults but
lighter tan in juveniles. Nacre is
white.
Similar species: There are no other
Nebraska species that can be confused
with this one.
Conservation status: G5, N5, SNR.
The map shows that the Threeridge
was once common in southeast
Nebraska. Live specimens have
recently been found in the Missouri
River below Gavins Point Dam.
Hosts: Black crappie, bluegill,
channel catfish, emerald shiner,
flathead catfish, freshwater drum,
green sunfish, largemouth bass,
northern pike, pumpkinseed, rock
bass, sauger, shortnose gar, spotfin
shiner, white bass, white crappie,
yellow perch.
Habitats used: Small to large rivers
and impoundments in mud, sand or
gravel (Cummings and Mayer 1992).
Creeks to large rivers in soft or coarse
substrates (Seitman 2003). Primarily
found on gravel or gravel-mud
substrates (Oesch 1995). Small
streams to large rivers as well as
lakes, rivers and streams in areas
with minimal to strong currents. Can
be found on clay, mud, sand,
sand/gravel, and gravel. Most
common on sand and gravel in 0.3 to
1m depth. (Parmalee and Bogan
1998). Firm substrates in creeks,
rivers, or lakes in fast or slackwater
areas (Watters et.al. 2009),
Native range: The Mississippi River
basin from Texas into Manitoba to
NewYork. Also found in St. Lawrence
River, tributaries to Great Lakes, the
Red River of the North and the Gulf
Coast drainages in Mississippi,
Louisiana and Texas.
Nebraska collection notes: Relict
and dead shell of this species is fairly
common in the Nemaha River basin.
It has also been found in a few
locations in the Big Blue and Elkhorn
River basins as relict shell. The only
recently collected live or fresh dead
specimens have been from the upper
Missouri River below Gavins Point
Dam.
Comments: That this species is doing
so poorly is a mystery as it should be
doing ok based on its broad range of
host fishes and habitat preferences.
