Pleurobema hanleyianum

Georgia Pigtoe

FWS Focus

Overview

Characteristics
Overview

Freshwater mussels serve at the base of the food web and provide a variety of ecosystem services. They filter our water for us, help stabilize the bottom of our rivers and serve as water quality indictors. Unfortunately, due to many anthropogenic affects, freshwater mussels are one of the most imperiled groups of animals in the world. The Georgia pigtoe, Pleurobema hanleyianum, is a freshwater mussel in the family Unionidae and endemic to the Coosa River drainage of the Mobile River Basin in Alabama, Georgia, and Tennessee. The Georgia pigtoe was listed in 2010 as endangered due to population decline, and has disappeared from 90 percent or more of its historical range, primarily due to the impoundment of riverine habitats

Scientific Name

Pleurobema hanleyianum
Common Name
Georgia pigtoe
FWS Category
Clams
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Food

Characteristics
Food

Although the diets of freshwater mussels are poorly understood, it is believed to consist of algae, and or, bacteria. Some studies suggest that the diets of freshwater mussels may change throughout their life, with juveniles collecting organic materials from the substrate though pedal feeding and then developing the ability to filter feed during adulthood. Pedal feeding is a form of deposit feeding where the animal uses their muscular foot to bury into the sediment, collecting organic matter. Filter feeding is a process by which mussels feed off suspended organic material by pumping in water through their incurrent aperture and out through their excurrent apertures, capturing the particles and using them as food.

Characteristic category

Behavior

Characteristics
Behavior

Many freshwater mussels spend the majority of their life sedentary and filter feeding on the bottom of rivers and streams. Sometimes they will bury into the sediment, only revealing a small portion of their aperture, which is used for gas exchange and filter feeding. 

Characteristic category

Physical Characteristics

Characteristics
Size & Shape

The shell of the Georgia pigtoe is oval to elliptical and somewhat inflated. The shell of adults reach about 50 to 65 millimeters (mm) (2 to 2.5 inches (in)) in length. The posterior ridge of the shell is low and evenly rounded, when evident. The anterior end is rounded, while the posterior margin is bluntly pointed below. Dorsal and ventral margins are curved, and the beaks rise slightly above the hinge line.

Color & Pattern

The periostracum (membrane on the surface of the shell) is yellowish-tan to reddish-brown and may have concentric green rings. The beak cavity is shallow, and the shell interior is white to dull bluish-white.

Characteristic category

Life Cycle

Characteristics
Life Cycle

Freshwater mussels live an interesting multi-stage life cycle which depends upon a fish host to complete. Males release sperm into the water column, to be hopefully siphoned in by the incurrent aperture of the females, where the eggs held within her gills are then fertilized. Once the fertilized eggs start to develop, the female becomes inflated, or gravid. The fertilized eggs develop into glochidia, which is the mussels larval stage. This stage requires a fish host for transformation into the juvenile stage, which sometimes requires a little coaxing by females. Glochidia are housed in packets called conglutinates and often mimic a food source of the fishes within that ecosystem to lure the fish to bite. Once the fish bites, the glochidia clamp down onto the fish, becoming encysted, and feed from the fish for several weeks until dropping off as juveniles. The host fish for glochida of the Georgia pigtoe is currently unknown.

Characteristic category

Habitat

Characteristics
Habitat

Little is known about the habitat requirements or life history of the Georgia pigtoe; however, it is most often found in shallow runs and riffles with strong to moderate current and coarse sand-gravel-cobble bottoms.

River or Stream

A natural body of running water.

Characteristic category

Similar Species

Characteristics
Similar Species

The Georgia pigtoe most similarly resembles the southern pigtoe, Pleurobema georgianum, but is more enlongate.

Geography

Characteristics
Range

The Georgia pigtoe is endemic to the Coosa River drainage of the Mobile River basin in Alabama, Georgia, and Tennessee. It has disappeared from 90 percent or more of its historical range, primarily due to the impoundment of riverine habitats. It is currently known from a few isolated shoals in the Upper Conasauga River in Murray and Whitfield counties, Georgia; in Polk County, Tennessee; and in the Big Canoe and Little Canoe creeks in St. Clair and Etowah counties, Alabama. Single records have been documented from the Weiss Bypass of the Coosa River (2002) and from Hatchet Creek (2001), though more surveys are required before it can be confidently declared that Georgia pigtoe populations exist at these locations.

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Timeline

Explore the information available for this taxon's timeline. You can select an event on the timeline to view more information, or cycle through the content available in the carousel below.

20 Items

Listing

Listing

Listing

Listing

Listing

Listing

Listing

Listing

Listing

Listing

Listing

Critical Habitat

Notice

Notice

Listing

Critical Habitat

Recovery Plan

Recovery Plan

Five Year Review

Recovery Plan

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Listing

Oct 25, 1999

Oct 25, 1999 Listing
Review of Plant and Animal Taxa That Are Candidates or Proposed for Listing as Endangered or Threateโ€ฆ
  • Publication type: CNOR
Item 1

Listing

Oct 30, 2001

Oct 30, 2001 Listing
ETWP; Review of Plant and Animal Species That Are Candidates or Proposed for Listing as Endangered oโ€ฆ
  • Publication type: CNOR
Item 2

Listing

Jun 13, 2002

Jun 13, 2002 Listing
Endangered and Threatened Wildlife and Plants; Review of Species That Are Candidates or Proposed forโ€ฆ
  • Publication type: CNOR
Item 3

Listing

May 4, 2004

May 4, 2004 Listing
Review of Species That Are Candidates or Proposed for Listing as Endangered or Threatened; Annual Noโ€ฆ
  • Publication type: CNOR
Item 4

Listing

May 11, 2005

May 11, 2005 Listing
Endangered and Threatened Wildlife and Plants; Review of Native Species That Are Candidates or Proโ€ฆ
  • Publication type: CNOR
Item 5

Listing

Sep 12, 2006

Sep 12, 2006 Listing
Review of Native Species That Are Candidates or Proposed for Listing as Endangered or Threatened; Anโ€ฆ
  • Publication type: CNOR
Item 6

Listing

Sep 12, 2006

Sep 12, 2006 Listing (Warranted But Precluded: Resubmitted)
Review of Native Species That Are Candidates or Proposed for Listing as Endangered or Threatened; Anโ€ฆ
  • Publication type: 12m petition finding
Item 7

Listing

Dec 6, 2007

Dec 6, 2007 Listing
Review of Native Species That Are Candidates for Listing as Endangered or Threatened; Annual Noticโ€ฆ
  • Publication type: CNOR
Item 8

Listing

Dec 6, 2007

Dec 6, 2007 Listing (Warranted But Precluded: Resubmitted)
Review of Native Species That Are Candidates for Listing as Endangered or Threatened; Annual Noticโ€ฆ
  • Publication type: 12m petition finding
Item 9

Listing

Dec 10, 2008

Dec 10, 2008 Listing
Review of Native Species That Are Candidates for Listing as Endangered or Threatened; Annual Noticโ€ฆ
  • Publication type: CNOR
Item 10

Listing

Jun 29, 2009

Jun 29, 2009 Listing (Endangered)
Proposed Endangered Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, and Rough Hornsnaiโ€ฆ
  • Publication type: Proposed
Item 11

Critical Habitat

Jun 29, 2009

Jun 29, 2009 Critical Habitat
Proposed Endangered Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, and Rough Hornsnaiโ€ฆ
  • Publication type: Proposed
Item 12

Notice

Feb 10, 2010

Feb 10, 2010 Notice
Proposed Rule: Listing with Designation of Critical Habitat for the Georgia Pigtoe Mussel, Interruptโ€ฆ
  • Publication type: Public Hearing
Item 13

Notice

Feb 10, 2010

Feb 10, 2010 Notice
Proposed Rule: Listing with Designation of Critical Habitat for the Georgia Pigtoe Mussel, Interruptโ€ฆ
  • Publication type: Comment Period Reopening
Item 14

Listing

Nov 2, 2010

Nov 2, 2010 Listing (Endangered)
Determination of Endangered Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, and Rough Hโ€ฆ
  • Publication type: Final
Item 15

Critical Habitat

Nov 2, 2010

Nov 2, 2010 Critical Habitat
Determination of Endangered Status for the Georgia Pigtoe Mussel, Interrupted Rocksnail, and Rough Hโ€ฆ
  • Publication type: Final
Item 16

Recovery Plan

Jul 3, 2013

Jul 3, 2013 Recovery Plan (Document Availability (non-FR))
Notice of Availability of a Technical/Agency Draft Recovery Plan for Georgia Pigtoe Mussel, Interruโ€ฆ
  • Publication type: Draft
Item 17

Recovery Plan

Nov 6, 2014

Nov 6, 2014 Recovery Plan (Document Availability (non-FR))
Endangered and Threatened Wildlife and Plants; Final Recovery Plan for Georgia Pigtoe Mussel, Interrโ€ฆ
  • Publication type: Final
Item 18

Five Year Review

Aug 30, 2016

Aug 30, 2016 Five Year Review (Information Solicitation)
5-Year Status Reviews of 22 Southeastern Species; Notice of initiation of reviews; request for inforโ€ฆ
  • Publication type: Notice
Item 19

Recovery Plan

Jun 27, 2019

Jun 27, 2019 Recovery Plan (Document Availability (non-FR))
Endangered and Threatened Wildlife and Plants; 29 Draft Recovery Plan Revisions for 43 Species in thโ€ฆ
  • Publication type: Draft
Item 20