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Transcript of NMUssels
Class: Bivalvia ~30,000 species
Order: Unionoida ~854 species
Family: Unionidae ~673 species
Southeastern US is the unionid hotspot of the earth
Shelled, benthic, long lived (10 to 40 yrs, but up to 100 years), filter feeders.
Often very abundent in benthic communities >100 g dry mass/m2 excluding shell
Shell production has been measured on the same magnitude of wood production in temperate forests (Gutierrez et al. 2003)!
Indicators of healthy aquatic systems Freshwater Mussels: An Overview Typical sexual dimorphism in Lampsilis siliquoidea.
Female: top and Male: bottom The kidneyshells (Ptychobranchous) tethers blackfly pupae-like ovisacs filled with glochidia to the stream bed. These ovisacs have evolved to resemble host prey items and increase probability of contact with host species, primarly darters. Life History Internal fertilization
Embryos develop into specialized larvae within the gills
Glochidia- obligate, more or less species specific parasites
Encystment on gills or fins
Adults Global distribution of Unionidae. Pie chart depics the diversity of the Order Unionoida, the family Uniondae represents 673 of the 854 species. Very large distribution. How can a clam disperse such great distances? Especially considering they are decendents of a marine ancestor and therefore must travel upstream. State of the Unionid Address Mussel species composition found in Harlow Lake and Harlow Creek. There were significantly more L. siliquoidea (121) than P. grandis (14) and E. complanata (4) (p<.001). Number of individuals of each species found at the three transects. Significantly more mussels were found at transect 3 (67) than at transect 1 (24) (p=.004). Likewise transect 2 (48) had significantly more individuals than transect 1(24) (p=.028). Sex compostion of L. siliquoidea found in Harlow Lake and Harlow Creek. There were significantly more males (77) than females (44) (p<.001). Average size of each speices found in Harlow Lake. P. grandis (115.6+/-16.3 mm) was significantly larger than L. siliquoidea (102.2+/-10.1 mm) (p=.011). Methods * * * * * * * * * Harlow Lake Mussel Survey Collect descriptive data Diversity
Sex ratio Hypothesis Mussel abundance will be positively correlated with depth Potential Factors Effecting Distribution Nine arbitrary sites
Three transects per site
Transect 1 (0-1 feet deep)
Transect 2 (1-2 feet deep)
Transect 3 (2-3 feet deep)
Visually and hand sampled
Collected all live individuals
along a 35 meter transect
Replacement in suitable habitat Map of Harlow Lake and Harlow Creek. Red asterisks represent collection sites. A total of 139 individuals were found in Harlow Lake (128) and Harlow Creek (11). Three species were found to inhabit Harlow Lake and Harlow Creek.
Lampsilis siliquoidea (left), Elliptio complanata (middle), Pygadon grandis (right) Male L. siliquoidea individuals (106.1±8.4 mm) were found to be significantly larger than the female individuals (95.3±9.0 mm) (p<.001). North Americas most endangered group of animals
69 % of the NA fauna is considered imperiled
At least 37 species have gone extinct since the beginning of the 19th century (Masters et al. 2000).
27 of the 45 species in Michigan are considerd endangered (13), threatened (6), or species of special concern (8) (MNFI 2009).
Anthropogenic changes to habitat are leading cause of decline. Decline acts synergistically with local decline of fish populations.
Freshwater mussel decline has been well documented and is fueling conservation effort.
Watershed surveys have been important in monitoring local populations. Varying water depths could concentrate distribution
May eat LOTS of unionoids
Nearly elimating entire pops. in small lakes and streams
(Diggens and Steward 2000, Zahner-Meike and Hanson 2001)
Optimal Foraging Theory
May effectly eliminate band of population along the shore line
(Jokela and Mutikainen 1995) Example of spatial refuge from the effects of muskrat predation,
from Jokela and Mutikainen (1995). Muskrats have eaten all of
the mussels near the shore, but large population still remains in
the center of the stream. Sex ratios can be variable, but are generally 1:1. Most
deviations in the ratio favor males (Berg et al. 2008) Simply broadcasting glochidia is a risky behavior. Many species have evolved incredible host attraction adaptations that increase the liklihood of encountering suitable hosts. The genus Epioblasma, the fish snappers, practice catch and release fishing.
Posterior edge modification is only present in females. Conclusions Acknowledgments Special thanks to the stream team, Scott Dietrich, Alex Duwe, Luke Obermeyer, and David Pfeiffer who’s help in sampling and design is sincerely appreciated. Also, Dr. Leonard for her guidance in methods and statistical analysis. ? References Berg, David J., Todd, Levine d., Stoeckel, James a., and Lang, Brain K. 2008. A conceptual model linking demography and population genetics of freshwater mussels. Journal of the North American Benthological Society 27(2):395-408. 2008
Graf, D. L. and Cummings, K. S. 2007. Review of the systematics and global diversity of freshwater mussel species (Bivalvia:Unionoida). Journal of Molluscan Studies 73: 291-314
Guitierz, J.L., C.G. Jones, D.L. Strayer and O.O. Iribarne. 2003. Mollusks as ecosystem engineers: Their fuctional roles as shell producers in aquatic habitats. Oikos 101: 79-90.
Jokela, J., and P. Mutikainen. 1995. Effect of size dependent muskrat (Ondatra zebithicus) predation on the spatial distribution of a fresh-water clam, Anodonta piscinalis Nilsson (Unionidae, Bivalvia). Canadian Journal of Zoology 73: 1085-1094
Master, L.L., B.A. Stein, L.S. Kunter, and G.A Hammerson. 2000. Vanishing assets: Conservation status of U.S. species. Pages 93-118 in B.A. Stein, L.S. Kunter and J.S. Adams (eds). Precious heritage: the status of biodiversity in the United States. Oxford University Press, New York.
Michigan Natural Features Inventory. Michigan’s Special Animals: Mussels, http://web4.msue.msu.edu/mnfi/data/specialanimals.cfm#grp15. Accessed 30 March 2010.
Strayer, D. L., 2008.Freshwater mussel ecology: a multifactor approach to distribution and abundance. University of California Press, California. p. 15. 139 individuals representing 3 species
Lampsilis siliquoidea dominated (males>females)
Mussel abundance correlated with depth (greater concentartion in deeper transects)
Varying water/ice depths and muskrat predations may concentrate distribution.
Many factors effect distribution (dispersal, habitat, hosts, food, predators, parasites).