Shell length of Dreissena polymorpha relative to substrate position.

Abstract

In the past 8 years since their discovery in Lake St. Clair, the invasive species Dreissena polymorpha has spread steadily throughout Lake Huron, Michigan, Superior, and many inland lakes in Michigan (Shankland et al., 2005). Understanding this species life cycle, morphology, and most of all behavior is essential in obtaining the goal of one day removing these foreign invaders from the Michigan lake system. Through understanding such behavioral criteria as how Dreissena colonizes an area, there is potential to illuminate the answers to the problems they pose in lake ecosystems. A post-veliger Dreissena larvae will attach to a substrate once it becomes too heavy to maintain a planktonic existence, and will, after colonization, compete for an ideal substrate position. In colonization on a cylindrical substrate such as a branch or log, the mean shell length of Dreissena increases as they are situated down the vertical axis of a substrate (p=6.29 E-58). Through the data analysis of field measurements of arc length and angle position, it is apparent that this relationship exists on cylindrical substrates. It was found that this relationship to substrate position is a consequence of mass (p=2.64, E-44) and length (p=6.29. E-58) distributions through intra-specific competition for ideal substrate space. Dreissena is ideally approaching the lower horizontal plane of a substrate, which, through the work presented here, was found to be its ideal habitat in terns of fitness. The results of this experiment apply to all lake ecosystems and are therefore critical in understanding some aspects of Dreissena behavior.