Date of Award

8-2006

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Judith M. Rhymer

Second Committee Member

Cynthia S. Loftin

Third Committee Member

Michael T. Kinnison

Abstract

The yellow lampmussel (Lampsilis cariosa) and tidewater mucket (Leptodea ochracea) are two species of freshwater mussels of conservation concern throughout their range. They are listed as Threatened in Maine, where their distribution is restricted to the Penobscot, St. George, and Kennebec River drainages, and are listed as Endangered, Threatened, or of Special Concern in several states throughout their range from Nova Scotia to Georgia. Like most freshwater mussels, they have an unusual life cycle during which their larvae (glochidia) are obligate parasites of specific fish species, and knowledge of host fish species is critical to freshwater mussel conservation. Previous laboratory studies have indicated that white perch (Morone americana) and yellow perch (Perca flavescens) are potential hosts for L. cariosa and white perch for L. ochracea. However, it is possible that other host fish species exist, and that some species are more effective hosts than others in the wild. The goal of this research was to determine if previously identified hosts act as host fish in natural populations and also to assess additional species as possible hosts by sampling naturally parasitized fish in the wild. Due to the small size of glochidia, morphological identification of the species of glochidia attached to fish can be very difficult or impossible. To identify glochidia attached to wild-caught fish, a species-specific molecular identification key utilizing restriction fragment length polymorphism (RFLP) patterns of the mitochondria1 ND1 gene was developed and tested for accuracy prior to sampling naturally parasitized fish. Naturally parasitized fish were captured at thirteen localities in the Penobscot, St. George, and Kennebec River drainages and inspected for glochidia infestations. The fish hosts identified under laboratory conditions for both mussel species were confirmed from naturally parasitized fish. Five additional fish species were also found to be potential hosts for L. cariosa, three of which are native species (banded killifish [Fundulus diaphanous], chain pickerel [Esox niger], and white sucker [Catostomus commersoni]) and two are introduced species (smallmouth bass [Micropterus dolomieu] and largemouth bass [Micropterus salmoides]). One species, the banded killifish, was a potential host for L. ochracea. For both mussel species, white perch was the most commonly and abundantly infested host fish, and several fish in multiple localities were found with heavy infestations of L. cariosa and/or L. ochracea glochidia. In contrast, only one individual of each of the other species of fish, including yellow perch, was found with L. cariosa or L. ochracea glochidia. This highlights the importance of identifying the important fish hosts for mussel populations in natural ecosystems, because yellow perch was previously identified as an effective host under laboratory conditions. Confirmed and potential host fish exhibited some degree of spatial and temporal variation within and among localities in Maine. The results of this study are crucial for understanding the complex ecological interactions between mussels and their hosts and for conservation planning.

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