Quagga, Zebra Mussels
The population of zebra mussels in Lake Michigan is declining because a more prolific relative appears to be taking its place. A new study from the University of Wisconsin-Milwaukee Great Lakes WATER Institute says that the quagga mussel seems to have nearly annihilated the zebra mussel population.
The zebra mussel, a native of the Caspian and Black Sea region, was first found in the Great Lakes in the late 1980s. The mussels quickly made their presence known, using the plankton upon which so many fish species depend.
The two species can be differentiated by morphological differences of the shell. Zebra mussels have a definite angle, or carina, between the ventral and dorsal surfaces, whereas, the quagga has a rounded carina. The ventral side of the shell of zebra mussels is flattened, but the quagga has a convex ventral side. This can sometimes be distinguished by placing shells on their ventral side; a zebra mussel will remain upright whereas a quagga mussel will topple over. Quaggas are rounder in shape and zebras are more triangular. The quagga mussel also has a small byssal groove on the ventral side near the hinge and the zebra mussel has a larger groove in the middle of the ventral side. Color patterns vary widely with black, cream, or white bands; a distinct quagga morph has been found that is pale or completely white in Lake Erie.
May 16, 2006 6:33 AM | Category: Animals