Triangle Floater

Distribution

The Triangle Floater is widely distributed throughout Virginia, with populations occurring in the Chowan, James, Potomac, Rappahannock, Roanoke, and York River basins.

Identifying Characteristics

• Thick, inflated shell; triangular in shape
• The anterior end is round, and the posterior end is pointed
• The ventral margin is round
• The outer covering of the shell (periostracum) is yellowish-green, darkening to black with age
• Rays are variable in width, and green to black in color
• The inner portion of the shell (nacre) may be white, pink, or red with iridescence

Habitat

The Triangle Floater inhabits small streams to large rivers and lakes. It is typically found in areas with slower moving current, and a stable substrate composition of coarse gravel and sand.

Life History

Freshwater mussels have a very unique life cycle. Parasitic larvae, called glochidia, develop in the gills of the female mussel. Once mature, the glochidia are expelled from the gills of the mussel and must attach to the gills of a suitable host fish, where they complete their transformation into a juvenile mussel. They then detach from the fish and begin their free-living existence on the river bottom.

Some freshwater mussels are host-specialists, meaning that metamorphosis can only occur on a limited number of closely related fish species, while others are host-generalists, with the ability to complete their life cycle using many different species. Female mussels employ a variety of strategies that “trick” their host fish into becoming “infested” with their glochidia. Some have elaborate mantle displays that protrude out of the shell that a fish attacks, while others release their glochidia in packets called “conglutinates” that resemble prey items that fish will ingest.

The Triangle Floater uses a wide variety of fish hosts including Common Shiner (Luxilus cornutus), Blacknose Dace (Rhinichthys cataractae), Largemouth Bass (Micropterus nigricans), Pumpkinseed (Lepomis gibbosus), Slimy Sculpin (Cottus cognatus), and White Sucker (Catostomus commersoni). Female Triangle Floater likely use a more passive approach to infest their host fish by broadcasting their glochidia into the water column, which then attach to the fins and gills of fish as they swim by.

Conservation

Both the Virginia Fisheries and Aquatic Wildlife Conservation Center (VFAWC) and Virginia Tech’s Freshwater Mollusk Conservation Center (FMCC) have propagated this species to augment populations throughout the Potomac River basin. Additionally, routine monitoring of Triangle Floater at release sites helps determine the success of these efforts and guide future management decisions.

Special Considerations

Freshwater mussels are extremely imperiled organisms. DWR regulates the take and possession of freshwater mussels occurring within the state. It is unlawful to take mussels from any inland waters in the Commonwealth except as provided for in §§ 29.1-418 and 29.1-568 of the Code of Virginia.