An International Journal of Ecology, Evolution and Environment

2010 JONES ET AL.: BIRDWING PEARLYMUSSEL LIFE HISTORY AND DEMOGRAPHY 337controlled, water-recirculating artificial streams with gravel-filled bottoms at the FreshwaterMollusk Conservation Center at Virginia Polytechnic Institute and State University,Blacksburg, to study life history. Depending on when mussels were collected, watertemperatures in the artificial streams were set at 15 to 20 C to mimic ambient rivertemperatures.The number of glochidia (fecundity) from 2 females collected in the Clinch River and 6females collected in the Duck River was estimated by flushing glochidia from the outer gillsof each female with a hypodermic needle filled with water. All glochidia were counted forsmaller females using a dissecting microscope to determine the number of glochidia/female to estimate fecundity. However, for the larger females, sub-samples of glochidia werecounted from 1 ml aliquots (n 5 3), and fecundity assessed volumetrically. Maturity of theglochidia was tested by exposing a small subset (,100) to a dilute salt solution (Zale andNeves, 1982). Glochidia were deemed mature when .20% exhibited rapid, sometimesmultiple, snapping responses when exposed to the NaCl solution. Dimensions (length 5anterior to posterior, height 5 dorsal to ventral) of 20 glochidia from each female musselwere measured using an ocular micrometer.Live female mussels were held in temperature-controlled (21–22 C) artificial streams forphoto-documentation. This laboratory set-up allowed females to display their mantle-lureand for behavioral observations of lure movements that were recorded under controlledconditions. All behavioral observations were made during daytime hours. Photographs ofthe mantle-lure were taken using a Nikonos V underwater camera with a 35 mm lens andKodak 200 Ektachrome film.Fish hosts.—Based on preliminary studies conducted by Hill (1986) and Watson (1999), wefocused primarily on testing various darter species and one species of sculpin as potentialhosts. Most of the fish were collected from the upper North Fork Holston River, ,1 kmabove Saltville, Smyth County, VA. Black sculpins (Cottus baileyi) were collected from theMiddle Fork Holston River at Atkins, Smyth County, VA. Gilt darters (Percina evides) werecollected from the Powell River, Lee County, VA, at the State Route 833 bridge where Lemioxrimosus was rare. All other fish collection sites had few mussels and no birdwingpearlymussels. Fishes were collected using low voltage (200–250 V) electroshocking toensure survival. Common and scientific names follow Robins et al. (1991) for fishes andTurgeon et al. (1998) for mussels.Methods for infesting fish with mussel glochidia generally followed Zale and Neves(1982). A plastic container 29 3 19 3 12 cm deep was used to hold fish during infestation.Fish of various species were held simultaneously in ,0.5 L of water, and glochidia from 1–3females were added to the container. The water in the container was constantly agitated byusing 2 air stones positioned on opposite sides for ,1 h. After infestation, fish wereseparated by species and placed in 38-L aquaria without substrate. Fish species were heldseparately at low densities (6–8/aquaria) in a water-recirculating fish-holding system. Thebottoms of the aquaria were siphoned every 2 to 3 d until juvenile mussels were firstcollected, and every 1 to 2 d thereafter. Juveniles were counted and placed in a culture dishwith sediment and algae for rearing. Collection of mobile juveniles confirmed that theglochidia had transformed on the fish species, and that species was a potential natural hostof Lemiox rimosus.Age and growth.—Fresh-dead shells of Lemiox rimosus were collected from various locationsin the Clinch and Duck rivers, TN between 1998 and 2007. Shells of various lengths werecollected to best represent the size-class structure of the population of each river. Thinsectionsof shells were prepared following procedures described by Clark (1980) and Neves