North Carolina Wildlife Resources Commission

Green Floater (Conrad, 1835)

Scientific Name: Lasmigona subviridis

Classification:  State Endangered

Photo Credit: NCWRC
   

Interior

 

Exterior 

NOTE: Hover over the bold words for definitions or see the Glossary.

This species was described by Conrad in 1835 from the Schuylkill River and other streams in Pennsylvania. The green floater is a small species; adults usually are less than 55 mm in length. Shells are thin and subovate or trapezoidal in shape. Beaks are depressed, projecting only a little above the hinge line, and may have double-looped sculpturing. The periostracum varies from dull yellow to brownish green. Numerous, variable width, dark green rays may be visible on the shell, especially in young specimens. The nacre is white with a bluish iridescent tinge posterior. In many specimens, yellow or salmon blotches occur in the nacre, both centrally and near the beak cavity. The shell is so thin that, when held up to a light source, the colors and patterns of the periostracum often show through the nacre. Hinge teeth are moderately developed but very delicate, and the lateral teeth may be incomplete or indistinct. The left valve has two lamellate pseudocardinal and two long, straight, thin, lateral teeth. The right valve has one pseudocardinal and one lateral tooth. The left valve often has an interdental projection.

 

Shell Anatomy

 

This species has a widespread distribution from the Cape Fear River Basin in North Carolina north to the Hudson River Basin, and westward through the Mohawk River and the Erie Canal to the Genesee River of New York. It also occurs in the New and Greenbrier rivers in North Carolina, Virginia, and West Virginia.

Distribution by County: Watauga River Basin: Watauga Co. (Watauga River Basin); New River Basin: Ashe Co. (New River Basin); Alleghany Co. (New River Basin). Neuse River Basin: Orange Co. (Eno River Subbasin), Person Co. (Flat R. Subbasin), Durham Co. (Flat R. Subbasin), Wake Co. (Swift Cr. and Little River subbasins). Roanoke River Basin: Person Co. (Mayo Cr. Subbasin), Halifax Co. (Roanoke River); Northampton Co. (Roanoke River); Rockingham Co. (Dan River Subbasin); Stokes Co. (Dan River Subbasin). Tar River Basin: Granville Co. (Tar River Subbasin), Nash Co. (Tar River Subbasin). NOTE: All headwater areas that flow into these occupied habitats should receive special management.

 


The green floater inhabits small to medium size streams. It is intolerant of very strong currents and often is found in quiet pools and eddies with gravel and sand substrate (Ortmann 1919). The green floater also has been found in canals. Walter (1954) found this species living in water depths of one to four feet. In North Carolina, the best populations are associated with good to excellent water quality.

The green floater is one of a few species of freshwater mussels that is hermaphroditic (individuals contain both male and female gonadal tissues). This species also is a bradytictic breeder, with the reproductive season extending from August to May. Host fish have not been determined for the green floater. However, there is documentation for direct transformation of glochidia into juvenile mussels (Barfield and Watters 1998, Lellis and King 1998).

General Life History For Mussels