The Earthworm Invasion
	Gina Marchini
	Earthworms are one of the most important components of soil biology, and have major effects, beneficial and detrimental, on ecosystems in which they occur. There are thousands of species of earthworms that live in the world, and they are native to many types of climates and are found in both terrestrial and aquatic habitats. Perhaps this combination of wide habitat range and the economic value and trade of the earthworm has contributed to its spread in habitats which were previously unoccupied by earthworm species.
	Earthworms are classified in the Phylum Annelida, Subclass Oligochaeta, Order Opisthophora, which is divided into 16 families. Ten of these families contain species known as earthworms, and four of those families are native to North America. Of these four families, about 70 species are native to the Eastern U.S. An additional 45 exotic species have been found in this region. Glaciations in the Pleistocene period wiped out all earthworm species present in Canada and the Northern Continental United States. The line the glaciers extended to in this period is known as the Wisconsin Glacier Line. The Southern limit of this line extends across Southern New York and Northern Pennsylvania. The Adirondack region of New York is located well inside the region glaciated during the Pleistocene, and species of earthworms occurring in the Adirondacks are not considered native. I studied areas within Huntington Wildlife Forest (HWF) in the central Adirondack region to determine where earthworms were located in the forest and possible explanations for their distribution pattern. In order to collect the earthworms, I used two different sampling methods. A type of chemical extraction was utilized by mixing 1/3 cup ground dry mustard with 1 gallon of water. The mixture was then poured onto the ground and the plot was watched for a total of 10 minutes. Any worms which came to the surface were collected in a plastic container and placed in a cooler. The second method, hand digging and sorting, was used on different plots than the mustard extraction. A 30cm deep hole was dug and all soil was placed on a plastic tarp. The soil was then hand sorted and any earthworms were collected were placed in a plastic container and then in a cooler. All earthworm species found in Huntington Wildlife Forest are members of the family Lumbricidae, and all are native to temperate regions in Europe. This enforces theories that earthworms are not following the retreat of the Pleistocene glaciers and recolonizing the Northern U.S. but are being brought from Europe through human introduction. Here is a list of the species I found:
					Alloloborophora chlorotica Apporrectodea longa Lumbricus castaneus Lumbricus rubellus Lumbricus terrestris Octolasion tytaeum
	It is quite possible that not all earthworm species in Huntington Wildlife Forest were collected during the two samplings which took place in June and July of 2006. Seasonal differences exist between earthworm populations and earthworm activity. The success of the mustard extraction technique depends on the activity of earthworms; if they are aestivating, earthworms will not be responsive. The earthworm clitellum is a regional swelling where gland cells secrete material during reproduction. The clitellum then slides off to form the cocoon in which young earthworms develop. This cocoon is very strong and small, and can be easily transported in soil, on cars or trucks, and through waterways. The cocoon can remain viable for many years until a suitable place for the earthworm to hatch is reached. Human transport is a major factor in earthworm transportation. Earthworms bought for fishing bait are often dumped still alive if they are not used, and earthworm cocoons may be present in soil or vegetation roots if planting is done in an area. Twenty-one sites in Huntington Wildlife Forest were chosen, and the ten of the sites where earthworms were located were places such as boat launches, old roads, trails, yards, and planting sites where humans had a major influence. Factors which were tested were leaf litter thickness, vegetative cover, and pH of the sites. On HWF, earthworms inhabited areas with higher pH on average than in places where earthworms were not present. Environmental factors which may affect earthworm populations have not been extensively studied and can differ between species. The pH of soil is often a determining factor in the distribution of species. Earthworms may also have an influence on soil structure and composition. Earthworm activity improves aeration and drainage, but can also lead to soil erosion by bringing very finely divided soil to the surface. Nutrient cycling in the soil can be altered by earthworm activity though the mixing of the litter layer with the organic soil layer. This redistribution of organic matter has been shown to cause changes in the ability of microbes to function in the soil. Microbial function is also affected by earthworm consumption, as some microbes cannot pass without harm through an earthworms’ system. Transmission of diseases by earthworms gained infamy when they were found to be vectors of foot-and-mouth disease to livestock in Europe. They are also host-to-host vectors of many other animal parasites, and can spread soil fungi and pathogens throughout the soil. Although earthworm species are highly influential on many temperate zone forests where they are not native, there are no specific regulations on earthworm imports into the United States. The Animal and Plant Health Inspection Service (APHIS) only regulates earthworm imports due to the potential of exotic plant pathogens being transferred along with them, and their sale within the U.S. is not regulated at all. In order to successfully preserve our ecosystems, it is important not to overlook the “little guys” and focus all efforts on attention grabbing exotic and invasive species. In the future, regulations on earthworm use for fishing should become a priority, as any exotic species which is being used and introduced in an area has the potential to upset the ecological balance.
	Contact Information
	Please contact me or the Adirondack Ecological Center at Huntington Wildlife forest if you have any questions or comments: gmarchini@gmail.com or aechwf@esf.edu
	About the Author: Gina Marchini
	I graduated from ESF with a B.S. degree in Conservation Biology in August 2006. In the future, I hope to participate in more research addressing invasive species and conservation issues.
	Here are some great links to reference if you are interested in the earthworm invasion: Minnesota Worm Watch
	Sources:
	Bohlen, P.J., Groffman, P.M., Fahey, T.J., Fisk, M.C., Sarez, E.S., Pelletier, D.M., Fahey, R.T. 2004. Ecosystem consequences of exotic earthworm invasion of north temperate forests. Ecosystems. 7:1-12. Dindal, D.L. 1990. Soil biology guide. New York: John Wiley and Sons. 1349 p. Edwards, C.A., Lofty, J.R. 1972. Biology of earthworms. London: Chapman and Hall Ltd. 283 p. Hendrix, P.F., Bohlen, P.J. 2002. Exotic earthworm invasions in North America: ecological and policy implications. Bioscience. 52: 1-11.