The influence of hydrological variability on the spatial distribution and orientation of freshwater mussels (Bivalvia: Unionidae).
An a priori selection of drainage basins in southwestern Ontario and southeastern Michigan was made using records of flow variability. The distribution and relative abundance of mussels (Bivalvia: Unionidae) was determined for three event (i.e., hydrologically flashy) and three stable (i.e., hydrologically stable) drainage basins. Multivariate analyses revealed that distinct mussel communities exist based on the hydrological variability of the river. Amblema plicata, Pyganodon grandis, and Fusconaia flava characterized event sites and Elliptio dilatata, Lampsilis radiata, and Lasmigona costata characterized stable sites. Apparently, some unionids can be associated with specific hydrological river types and their distribution can be predicted using flow-related stream attributes. The patterns of burrowing and orientation were examined in unionids with respect to hydrological variability. Most individuals in both river types were oriented with their siphons pointing upstream. Mussel orientation differed significantly between the two river types with event mussels orienting more parallel to the flow than those in the stable river. Mussels in the event river were significantly larger than those in the stable river, but the size of a mussel did not determine its orientation within a river. Burrowing depth did not differ for mussels between event and stable rivers. There is strong evidence to suggest that there is a preferred streamlined orientation by mussels in the more hydrologically variable river. This burrowing behaviour may enhance the streamlined nature of the unionids and lessen the force of the flow on them. Orientation of unionids to flow was examined in laboratory experiments to identify if orientations observed in the field reflected passive, flow-induced movements. (Abstract shortened by UMI.)Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1995 .D55. Source: Masters Abstracts International, Volume: 34-02, page: 0651. Adviser: Lynda D. Corkum. Thesis (M.Sc.)--University of Windsor (Canada), 1995.
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