North America contains the greatest diversity of freshwater mussels on the planet – roughly one third of all known species. Freshwater mussels are one of the most endangered faunal groups in the world. Seventy five percent of North American species are listed as being endangered, threatened or of special concern in all or parts of their range1. The number of species believed to have become extinct in North America over the past 100+ years is about 10% of the current number of extant species2. Pollution and dams are two major threats to freshwater mussels throughout North America. Mussels are notable for their unusual life histories in which the larval forms (glochidia) parasitisize a vertebrate host (generally fish). In a number of species, elaborate structures and mechanisms have evolved to promote successful contact between glochidia and fish.
Ten of the approximately 300 North American species are found in Maine. Two of these are listed as threatened within the state (yellow lampmussel and tidewater mucket), while three are of special concern. Maine’s ten species belong to two families and eight genera.
(1) Williams, J.D., M.L. Warren, K.S. Cummings, J.L. Harris, and R.J. Neves. 1992. Conservation status of freshwater mussels of the United States and Canada. Fisheries 18(9): 6-22.
(2) Bogan, A.E. 1993. Freshwater bivalve extinctions (Mollusca: Unionidae): a search for causes. American Zoologist 33: 599-609.
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