Pistolgrip (Mussels of the Upper Green River, KY)

Pistolgrip

Tritogonia verrucosa

Diagnostic description ³

Several characters distinguish the pistolgrip from most other North American mussel species. The shell is generally thick, large (up to 180 mm), rectangular to elongate, nearly covered in pustules, possesses an elevated posterior ridge, and is dark green, brown or black in color (Cummings and Mayer 1992, Parmalee and Bogan 1998, Watters et al., 2009).

Distribution ⁴

Tritogonia verrucosa, the buckhorn (also called pistol grip), is found in the Neartic region. Buckhorns have been documented in the mid and eastern parts of the United States, including: Texas, Pennsylvania, Tennessee, Mississippi, Kentucky, Georgia, Alabama, Minnesota, Missouri, Iowa, Arkansas, Louisiana, Maryland, Oklahoma, Delaware, North Carolina, Ohio, Indiana, Wisconsin, Illinois, West Virginia, and Virginia.

Biogeographic Regions: nearctic (Native )

Habitat ⁵

The pistolgrip usually inhabits the mud, sand, or gravel substrate of small to large rivers in areas with moderate current and good water quality (Cummings and Mayer 1992, INHS 1997, Williams et al., 2008, Watters et al., 2009, MDNR 2011).

Morphology ⁶

Adults: This species has several distinctive characteristics that separate it from similar North American mussels. Pistolgrip can reach a length of 20.3 cm (8 in). The most distinctive features of the shell are its elongate outline, thick valves, numerous irregular pustules, and prominent posterior ridge. The dorsal margin of the shell is straight or slightly curved, and the ventral margin is usually arched. The outside of the shell is green to light brown in young individuals and becomes dark brown to black with age. Inside of shell is white and iridescent posteriorly. Pseudocardinal teeth are large, serrated, and well-developed; lateral teeth are long, straight, and striated. The left valve has both two psuedocardinal teeth and two lateral teeth while the right valve has one of each. Posteriorly, females are more rounded and compressed while males are more truncated (Cummings and Mayer 1992, INHS 1997, Parmalee and Bogan 1998, Sietman 2003, Williams et al., 2008, Watters et al., 2009, MDNR 2011).

Glochidia: The glochidial, or larval, form of pistolgrip is very tiny, with a height ranging from 113 to 125 μm. They have subelliptical valves, a rough surface, and a slightly concave dorsal margin (Hove et al., 2011).