My interest is understanding the structure and function of gills in freshwater mussels. Gills of most freshwater bivalves are involved in respiration, feeding, reproduction and osmoregulation. In the unionid mussels, I have identified and characterized extracellular calcium concretions in the gills, offering a model for calcium phosphate mineralization. My students and I study the structure and chemical properties of the concretions and their role in physiology. Mechanisms under investigation include cellular secretion of concretions, mobilization of concretions during reproduction, calcium binding properties of concretion protein, and mechanisms involved in concretion turnover.
We are also interested in the structure-function relationships involved in suspension feeding in these bivalves. We are characterizing differences in the ability of various freshwater and marine bivalve species to capture varying size particles and relating this to the structural differences between the gills of various species. Of particular interest is the apparent ability of the D. polymorpha to more effectively utilize bacteria than other freshwater species.
These studies integrate morphological and physiological data to define functional characteristics of gills. Recently, we have been studying the musculature and supporting tissue in the gills. The motor responses to neurotransmitter application provide insight in the dynamic changes in gill structure that would allow regulation of water flow through the gills. These studies allow us to define, compare and contrast regulatory mechanism and strategies among the bivalves.
Medler, S., C. C. Thompson, T. H. Dietz, and H. Silverman. 1999. Ionic effects on intrinsic gill muscles in the freshwater bivalve, Dreissena polymorpha. Comp. Biochem. Physiol. A. 122: 163–172.
Dietz, T. H., D. S. Neufeld, H. Silverman, and S. H. Wright. 1998. Cellular volume regulation in freshwater bivalves. J. Comp. Physiol. B 168: 87–95.
Medler, S., and H. Silverman. 1997. Functional organization of intrinsic gill muscles in zebra mussels, Dreissena polymorpha (Mollusca: Bivalvia), and response to transmitters in vitro. Invert. Biol. 116: 200-212.
Beninger, P. G., J. W. Lynn, T. H. Dietz, and H. Silverman. 1997. Mucociliary transport in living tissue: The two-layer model confirmed in the mussel, Mytilus edulis L. Biol. Bull. 192: 4-7.
Silverman, H., S. J. Nichols, J. S. Cherry, E. Achberger, J. W. Lynn, and T. H. Dietz. 1997. Clearance of laboratory–cultured bacteria by freshwater bivalves: differences between lentic and lotic unionids. Can. J. Zool. 75: 1857–1866.