The Mussel–Fish Relationship: A Potential New Twist in North America?

Abstract

North American freshwater mussels are critically imperiled organisms that generally require fish hosts in order to complete their life cycle. Although numerous studies have focused on the parasitic relationship between mussels and fishes, few have examined the benefits that mussels provide to other organisms. During sampling of Altamaha River, Georgia, we observed foreign eggs occurring within body cavities of native mussels across a 253-km reach of the river basin. Eggs were recovered from 6% of the 757 mussels examined among seven sites. Foreign eggs were present in 17% and 18% of examined mussels at two sites. Using molecular techniques, eggs were identified as American Shad Alosa sapidissima. This discovery appears to be the first documented occurrence of native fish eggs in live North American mussels. Further research into the nature and mechanism of this symbiosis is warranted to assess whether this relationship is amensalistic, mutualistic, or commensalistic as American Shad and many freshwater mussels are species of conservation concern. A commensalistic or mutualistic relationship between these taxa may result in restoration activities affecting one species facilitating restoration of others.

Received August 3, 2012; accepted December 30, 2012

ACKNOWLEDGMENTS

We thank Deb Weiler for her field assistance and data processing during this study. We thank Robert Bringolf for laboratory assistance and reviewing this manuscript. The manuscript was improved with suggestions from anonymous reviewers. We also thank The Environmental Resources Network for the purchase of essential field equipment used in completing this study. This project was funded through the State Wildlife Grant Program in cooperation with the U.S. Fish and Wildlife Service, Georgia Department of Natural Resources, Department of Genetics at the University of Georgia, and the D. B. Warnell School of Forestry and Natural Resources.