FEEDING AND BURROWING BEHAVIORS OF JUVENILE RAINBOW MUSSELS, VILLOSA-IRIS (BIVALVIA, UNIONIDAE)

This study characterized the relationship between juvenile rainbow mussels (Villosa iris) and the sediment they inhabit. Dye studies in a feeding chamber, video recordings of feeding, and gut content analysis were used to determine mechanisms of feeding, the primary food source, and the origin of substances taken up by 1- 14-d-old juveniles. Within 20 min of placement, 98.5% of the juveniles were able to burrow in the sediment. Although juveniles burrowed < 1 cm into the sediment, they were not exposed to the overlying water. Exposure to sediment comes not only through direct contact, but also through filtration of interstitial water and sediment-associated fine particulate organic matter. juveniles fed on bacteria and bacterial-sized particles as well as algae. Their predominant food source appears to vary with age. Pedal-locomotory and pedal-sweep feeding behaviors are used to facilitate movement of particles into the pedal gape. Pedal-locomotory behaviors were used more frequently in the presence of detrital particles while pedal-sweep feeding was most frequently observed in a tri-algal suspension.