Colonization of unionid bivalves by the zebra mussel


Tucker, J. K.  1995.  Colonization of unionid bivalves by the
zebra mussel, Dreissena polymorpha, in Pool 26 of the Mississippi
River.  Journal of Freshwater Ecology 9(2):129-134.1  Windrow
formation of two snails (families Viviparidae and Pleuroceridae)
colonized by the exotic zebra mussel, Dreissena polymorpha. 
Journal of Freshwater Ecology 9(1):85-86.2  Reprinted by the
National Biological Service, Environmental Management Technical
Center, Onalaska, Wisconsin, January 1995.  LTRMP 95-R001.  8 pp.
(NTIS #PB95-195111)


ABSTRACT

1The relationship between 18 species of native unionid bivalves
and the exotic zebra mussel, Dreissena polymorpha, was explored
at a monitoring site in Pool 26 of the Mississippi River. From
1992 to 1993, colonization rates increased from 27% to 99.7% of
unionids, and the mean number of D. polymorpha per unionid
increased from 2.2 to 37.4. The number of D. polymorpha per
unionid shell was related to shell length and varied among
species. Four types of colonization patterns were found, each
differing from the others in the relative number of colonizing D.
polymorpha. Shell and ornamentation types were differentially
colonized. Thick-shelled, ornamented species were more heavily
colonized than were thin-shelled, unornamented species. Habitat
alteration of the gravel bar site was profound, with the zebra
mussels forming a pavement over the gravel bar. This resulted in
adverse effects on the unionids. Once mussels exited the
substrate, they were unable to penetrate the entangled mass of
zebra mussels and pebbles. Consequently, unionids were exposed
when water levels fell, and considerable mortality occurred.

2Colonization of two species of native gastropods, Campeloma
crassulum (Viviparidae) and Pleurocera canaliculatum
(Pleuroceratidae), by the exotic zebra mussel (Dreissena
polymorpha) was documented for the Mississippi River and Illinois
River in Illinois.  Wind- and boat-generated waves created
windrowed deposits of these snails.  Nearly all snails collected
retained intact zebra mussels or evidence of mussel attachment.


KEYWORDS

1zebra mussel, Mississippi River, Pool 26, colonization, unionid
2windrows, gastropod, zebra mussel