Listing
Oct 25, 1999
Oct 25, 1999 Listing
Review of Plant and Animal Taxa That Are Candidates or Proposed for Listing as Endangered or Threate…
- Publication type: CNOR
Item 1
FWS Focus
Overview
Characteristics
Overview
The Alabama pearlshell (Margaritifera marrianae) is a medium-sized freshwater mussel known from a few tributaries of the Alabama River and Conecuh/Escambia River drainages in south central Alabama, as documented by R.I. Johnson in 1983 and later by J.D. Williams and others in 2008. The Alabama pearlshell is one of five North American species in the family Margaritiferidae. Prior to 1983, the Alabama pearlshell was thought to be the same species as the Louisiana pearlshell (Margaritifera hembeli), as documented by Conrad in 1838 and later by Simpson in 1914, as well as Clench and Turner in 1956, a species now considered endemic to central Louisiana.
Scientific Name
Margaritifera marrianae
Common Name
Alabama pearlshell
FWS Category
Clams
Identification Numbers
Characteristics
Characteristic category
Physical Characteristics
Characteristics
Color & Pattern
It ranges in coloration from olivaceus or blackish brown to yellowish brown. The inside nacre is white to purplish and moderately iridescent.
Size & Shape
The Alabama pearlshell is medium in size the outside of the shell, called the periostracum, is smooth, shiny and somewhat roughened along the posterior slope.
Measurements:
Length: 3.7 in (95 mm)
Characteristic category
Habitat
Characteristics
Habitat
The Alabama pearlshell has been found in small headwater streams with slow to moderate current and substrates that consist of mixed sand, gravel or sandy mud. Most stream locations where Alabama pearlshell are found either have no aquatic vegetation or have limited quantities of Ludwigia spp., Justicia spp., and or filamentous algae, as documented by D.N. Shelton in 1996, and as T.B. Fobian described in 2013, can be characterized by braided channeling or by stable pools and riffles. These streams are generally between 3 and 6 meters wide with a typical water depth of less than 1 meter, as documented by D.N. Shelton in 1996.
Characteristic category
Food
Characteristics
Food
Freshwater mussels use a siphon to filter algae, bacteria, phytoplankton and other particles from the water column.
Characteristic category
Similar Species
Characteristics
Similar Species
Characteristic category
Life Cycle
Characteristics
Life Cycle
The Alabama pearlshell has a unique life cycle that is similar to other species of freshwater mussels. Males release sperm into the water column to fertilize females. Females filter sperm from the water and brood fertilized eggs, which develop into microscopic larvae called glochidia, in their gills. Females release glochidia when they detect the presence of fish. The glochidia attach themselves to the fish’s gills and become parasites for some time, which can range from several days to weeks. Once they have transformed into microscopic juveniles, they fall off of the fish’s gills and settle into substrate at the bottom of a stream or river.
Reproduction
Field observations noted by Alabama Department of Conservation and Natural Resources biologists and laboratory studies conducted at the Alabama Aquatic Biodiversity Center have concluded that female Alabama pearlshell brood their eggs in early to mid-March. Biologists have also identified redfin pickerel (Esox americanus) and chain pickerel (Esox niger) as good laboratory host fishes for this species.
Geography
Characteristics
Range
Since the Alabama pearlshell was first collected in the early 1900s, it has only been found in the Alabama and Conecuh/Escambia River basins in south central Alabama.
Timeline
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