FWS Focus

Overview

Characteristics
Overview

The green floater is a small freshwater mussel found in small streams and large rivers in the eastern United States. It is historically native to the District of Columbia and 10 states: Alabama, Georgia, Maryland, New Jersey, New York, North Carolina, Pennsylvania, Tennessee, Virginia, and West Virginia. Today, however, green floaters are considered extirpated in Alabama and Georgia, and there are no recent records from?New Jersey or the District of Columbia. 

Scientific Name

Lasmigona subviridis
Common Name
green floater
FWS Category
Clams
Kingdom

Location in Taxonomic Tree

Identification Numbers

TSN:

Characteristics

Characteristic category

Habitat

Characteristics
Habitat

Green floaters prefer streams with slow to medium flows and good water quality. They are often found in sand or small gravel substrates where they establish a foothold and bury themselves as deep as 15 inches. They have limited mobility, and fast-flowing currents or high-water events can cause them to be washed downstream. When they occur in larger streams and rivers, they are found in quieter pools and eddies, away from strong currents.

River or Stream

A natural body of running water.

Characteristic category

Physical Characteristics

Characteristics
Size & Shape

Green floaters are small freshwater mussels with ovate trapezoidal shaped shells. Adults rarely exceed 2.2 inches. 

Color & Pattern

Green floater shells are yellowish brown to olive green with green rays.

Characteristic category

Food

Characteristics
Food

Like all freshwater mussels, the green floater is an omnivore that feeds on a wide variety of microscopic particulate matter, namely bacteria and algae.

Characteristic category

Life Cycle

Characteristics
Reproduction

Green floaters are hermaphroditic and have the ability to self-fertilize, which increases the probability of fertilization. Spawning and reproduction occur during the late summer or early fall. In the winter, green floaters can directly metamorphose larvae, called glochidia, meaning that adults keep the glochidia in their gills until they mature into juveniles and then release them into the water column in the spring. For most freshwater mussels, glochidia are released into the water column and must attach to the gills of a host fish in order to undergo metamorphosis and transform into juveniles. Several weeks or months later, the juveniles detach from the fish and burrow into the substrate. Green floater adults have the ability to expel glochidia that use fish hosts, too, but it is not known what proportion of green floaters use this method of reproduction. The added ability to directly metamorphose glochidia without requiring an intermediate fish host is unique to the green floater. This life strategy may allow the green floater to occur in small streams with small populations and few fish, although the use of fish hosts is necessary for periodic upstream dispersal. 

Life Span

The green floater is a short-lived, fast-growing species compared to similar mussels. Green floaters typically live just three to four years. 

Geography

Characteristics
Range

The green floater is still found in seven of the 10 states within is native range: Maryland, New York, North Carolina, Pennsylvania, Tennessee, Virginia, and West Virginia. There are no recent records of green floater from New Jersey or Washington D.C., and it is considered extirpated from Alabama and Georgia and from some rivers in other parts of its range.

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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.

7 Items

Listing

Listing

Listing

4d

Critical Habitat

Listing

Listing

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Listing

Nov 21, 1991

Nov 21, 1991 Listing
ETWP; Animal Candidate Review for Listing as Endangered or Threatened Species; 56 FR 58804 58836
  • Publication type: CNOR
Item 1

Listing

Nov 15, 1994

Nov 15, 1994 Listing
ETWP; Animal Candidate Review for Listing as Endangered or Threatened Species.
  • Publication type: CNOR
Item 2

Listing

Sep 27, 2011

Sep 27, 2011 Listing (Substantial)
Partial 90-Day Finding on a Petition To List 404 Species in the Southeastern United States as Endang…
  • Publication type: 90 day petition finding
Item 3

4d

Jul 26, 2023

Jul 26, 2023 4d
Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for…
  • Publication type: Proposed
Item 4

Critical Habitat

Jul 26, 2023

Jul 26, 2023 Critical Habitat
Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for…
  • Publication type: Proposed
Item 5

Listing

Jul 26, 2023

Jul 26, 2023 Listing (Warranted)
Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for…
  • Publication type: 12m petition finding
Item 6

Listing

Jul 26, 2023

Jul 26, 2023 Listing (Threatened)
Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for…
  • Publication type: Proposed
Item 7