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Archive of Featured Species

Featured Species: Mountain creekshell (Villosa vanuxemensis)

The mountain creekshell is a small freshwater mussel, with adults measuring between 40-65 mm (1.5-2.5 inches). The exterior of the shell, called the periostracum, can range from olive, to light brown or black. Younger animals may have fine rays marking their shell, but the lines are less visible as the animal reaches adulthood. This species is sexually dimorphic, meaning males and females can be differentiated by looking at their shell. Females have a prominent swelling on the lower posterior margin, and a point near the top of the posterior margin creating a triangular shape. Male shells are usually more oval shaped and lack the swelling the females need to accommodate brooding gills full of larvae. The interior of the animal's shell, called the nacre, is usually purple but can also be coppery in color.

The mountain creekshell is a long-term brooder, also called bradytictic, meaning animals spawn in the late summer to early fall. Gravid females hold their larvae over winter (September - July). In the wild its host fish species include sculpin, a small bottom-dwelling fish, and rock bass.

The mountain creekshell can be found in parts of Virginia, Tennessee, Kentucky, North Carolina and Georgia, primarily in tributaries of the Tennessee River (Clinch, Powell, and Holston Rivers in Virginia). Animals are often found along river banks in slow moving water with substrate high in organic matter, but can also be found in sandy substrates in riffles. This species is also found in small headwater creeks.

At the Aquatic Wildlife Conservation Center, the mountain creekshell is propagated using sculpin. In 2009, over 8,100 juveniles were produced. Currently, over 1,900 are being held at AWCC to be tagged and released this year in the Clinch River. Although is not listed as endangered, the mountain creekshell is typically uncommon where it occurs. Our efforts will boost wild numbers to ensure that this species persists well into the future.

Featured Species: Fluted kidneyshell (Ptychobranchus subtentum)

The fluted kidneyshell is a large freshwater mussel with adults measuring between 80-130 mm (3-5 inches). Shell color ranges from yellow-green to brown and is marked with wide green rays. This species is not sexually dimorphic, meaning males and females cannot be differentiated by looking at the shell. The interior of the shell, called nacre, can range from white to pink or salmon in color.

The fluted kidneyshell is a longterm brooder, meaning animals spawn in the summer and larvae are held over winter (October - July). Females package larvae (also called glochidia) in conglutinates that look like blackfly pupae. Once conglutinates are released (believed to be triggered by water temperature), they snag on rocks on the stream bottom. Each packet contains several hundred larvae. When fish feed on the packets, they burst open, releasing larvae in the fish's mouth. Host fish include redline darters and fantail darters.

The fluted kidneyshell is currently a candidate for federal listing. On a state level, the species is listed as imperiled in Virginia and Tennessee, and critically imperiled in Kentucky.

At AWCC the fluted kidneyshell is propagated using redline darters. In 2009, over 41,000 juveniles were produced. Several thousand are currently being held at AWCC for grow-out before being released in the Clinch and North Fork Holston rivers.

Featured Species: Spiny riversnail (Io fluvialis)

The spiny riversnail, a state threatened species, is a gill-breathing freshwater snail found in the Clinch, Powell and Holston river systems of southwest Virginia and northeast Tennessee. An adult spiny riversnail can live 15 years and grow to lengths of about 50 cm, making it one of the largest species of aquatic snails in North America. Limiting factors for this threatened species include impoundments, dams and declining water quality.

Spiny riversnails range in color from brown to olive green. The inside of their shell is sometimes marked by purple bands. The snails get their name from large, armored spines that grow on their shell. However, some populations lack spines. Spiny riversnails feed on algae and organic debris found on river rocks, making them an important factor in maintaining good water quality.

Females lay eggs in the spring when water temperatures begin to reach 60° F. Eggs are laid in whorls or lines on smooth surfaces and can be found on rocks and in empty mussel shells. Eggs are very small (0.35 mm or 0.01 inches) and are slate gray to deep purple in color, hatching in 15-20 days.

Between 2005 and 2008, nearly 11,000 spiny riversnails have been produced at AWCC and released into the Clinch and Powell rivers. These have ranged in age from 6 months to 2 years old. The spiny riversnail reached maturity at AWCC after 2 years.

Featured Species: oyster mussel (Epioblasma capsaeformis)

The oyster mussel is a federally endangered species that historically occurred throughout the Clinch and Powell river drainages of southwestern Virginia and northeast Tennessee. This species is approximately 5 cm (~1.97 inches) in length and yellow-green in color. The oyster mussel is sexually dimorphic, meaning that males and females are markedly different in appearance. Compared to males, females are more inflated and rounded at the posterior end of their shell, characteristics believed to aid in reproduction.

The oyster mussel is a long-term brooder, where spawning occurs in the summer and larvae are held by the female over winter until being released in the spring. Host fish include fantail darters, logperch and banded sculpin. Female oyster mussels have a fleshy flap inside their shell that ranges in color from white to pale blue. Tiny appendages at the top of the flap move, simulating aquatic insect movement, and attract host fish to the mussel. When a female senses a fish near, she closes her shell quickly, trapping the fish. The flaps close around the fish head, acting as a gasket, and the female begins pumping larvae from her gills. After a few minutes the mussel releases her grip, and the fish swims away carrying tiny mussel larvae.

To date, the AWCC has propagated 151,770 juvenile oyster mussels and released 24,961. This species is one of many becoming increasingly rare in the rivers of southwestern Virginia. The oyster mussel was also affected by the coal slurry spill that occurred in Lee County, Virginia in 1996. For propagation purposes, broodstock are collected from the Clinch River in Tennessee where populations are abundant, with the majority of juveniles released in streams in southwestern Virginia.