Mitigating the Spread of Zebra Mussels into Wetlands from Mississippi River Diversions.

William F. Font

If one were to select a poster child to represent alien species, the zebra mussel, Dreissena polymorpha, might be a good choice.  The zebra mussel epitomizes an exotic invader that conforms to the definition of an aquatic nuisance species.  Furthermore, although most Americans are notoriously ignorant of, or indifferent to, the consequences of exotic species, knowledge of the zebra mussel’s harmful ecological and economic impacts is widespread outside of the scientific community.

The main objective of this research is to determine if the zebra mussel has dispersed or has the potential to disperse in Louisiana from the Mississippi River into adjacent wetlands.

Among these biological control factors, the primary emphasis will be placed upon documentation of the presence of parasites that are already present in Louisiana wetlands that have the potential to infect zebra mussels and impede their dispersal.  The m

ajor source of parasites that might control the spread of this alien species of mussel are parasites of native mussels that presently occur in Louisiana wetlands.  The native mussels species that stands out as the most promising candidate is Conrad’s false mussel, also known as the dark mussel, Mytilopsis leucophaeta because it is the sister species (i.e. its closest relative) to the zebra mussel.  Among the various taxonomic groups of parasites that have the potential to both infect and control populations of mussels, digenetic trematodes represent the parasites that are most likely to be effective.  Digenetic trematodes, commonly known as flukes, almost invariably use molluscs as first intermediate hosts in their life cycles.  Although most trematodes utilize snails as first intermediate hosts, some species of flukes parasitize members of the Class Pelecypoda (=Bivalvia) which includes, clams, mussels, oysters, and their relatives.  Of greatest importance to their potential role as control agents, the trematode life cycle stages that infect molluscs, sporocysts and rediae, are almost invariably parasitic castrators, that is, they totally destroy the reproductive ability of infected hosts.  For this reason, this group of parasites offers the greatest promise to serve as a biological agent that mitigates the spread of zebra mussels from the Mississippi River into Louisiana wetlands.