Degree Name

Master of Science (MS)

Semester of Degree Completion

1998

Thesis Director

Kipp C. Kruse

Abstract

Burrowing behavior of unionids was examined as a variable in colonization of unionids by juvenile zebra mussels searching for substrate. For each unionid species represented, zebra mussel densities were compared between a free-living experimental unionid and an immobilized control during each replicate. Of the four species used (Amblema plicata, Quadrula quadrula, Leptodea fragilis and Obliquaria reflexa), only Q. quadrula had a statistically significant difference between zebra mussel densities on the experimental mussels as compared with the controls. When zebra mussel densities on the experimental mussels were compared between species, only the comparison of Q. quadrula and O. reflexa was significantly different. Q. quadrula and O. reflexa have very different burrowing strategies but the behavior of A. plicata was virtually identical to that of Q. quadrula and yet, was not statistically different from O. reflexa . Other possible explanations could include shell thickness or ornamentation or some combination of any or all of the three possible explanations (thickness, ornamentation and burrowing behavior). However, neither thickness nor ornamentation can be used individually as explanations in this situation since both Q. quadrula and O.reflexa are thick-shelled and ornamented. More investigation needs to be conducted.

In the second part of the project, unionids were used as potential substrate to discover of juvenile zebra mussels would relocate from one substrate to colonize a live unionid. Four object types were used (log, aluminum beverage can, rock and empty unionid shell). In each replicate, two of the same object type with 25 zebra mussels already attached to each were placed in close proximity to a live unionid. Out of 800 zebra mussels, only one relocated to the live unionid. The other 38 that became displaced either reattached to their previous object or attached to the experimental apparatus. Unionids do not appear to be a strong enough attraction as substrate to cause attached zebra mussels to relocate.

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