Illinois Natural History Survey - University of Illinois

Oligochaetology

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"Oligochaete! Thou taxonomic pain!

My mouth and mind and memory affirm,
Twould be much less a stress upon the brain
To designate you merely as a worm..........
The object of my study is to try
To help both man and worm see eye to eye."
- D. N. Howell (1976)

Oligochaetology is the study of worms - specifically, the Class Oligochaeta within the Phylum Annelida. Other classes in the Phylum Annelida, the true segmented worms, include the Acanthobdellae (bristle worms), Aphononeura (suction-feeding worms), Branchiobdellae (crayfish worms), Hirudinea (leeches), and Polychaeta (sand worms, tube worms, and clam worms). Over 15,000 species of worms have been described worldwide; we now recognize 2,450 species in North America north of Mexico.

Worms occur in virtually all habitats where water is present, even in areas that are only slightly moist. Numerous species also occur exclusively on land. Most annelids are free-living, but many species are parasitic, mutualistic, or commensal during part of or throughout their life cycle.

Worms are an important and often dominant group in aquatic systems, providing a valuable food source for many other aquatic organisms; 131 species presently are known to occur in Illinois. As early as Aristotle, aquatic worms have been recognized for their ability to thrive in organically polluted waters, often forming dense colonies that resemble red waving carpets. Recent works have noted the presence of aquatic worms in almost every habitat that is associated with water, including pristine springs, streams, wells, seeps, and lakes, as well as industrially polluted harbors, large rivers, and waste retention ponds.

Earthworms, although numbering only about 30 species in Illinois, play an important role in the decomposition of organic matter, mineral cycling, and the aeration, drainage, and root penetration of the soil; through this activity, they also provide suitable habitat for smaller soil fauna, particularly micro-organisms. It has been estimated that earthworms can 'move' up to 18 tons of soil per acre each year. Abundance estimates of earthworms have been as high as three million per acre.


Most annelid research and projects are listed in the INHS Annual Report.

See our Publications Catalog for articles published at INHS.

Mark J Wetzel lists a variety of information on his homepage.


Some past articles published in INHS Reports:

INHS Annelid collection. March-April 1999

Illinois Earthworms: Indicators of Soil Health? May-June 1998

Horsehair Worms in Illinois. March-April 1995

Acanthocephalans and Rotifers Provide Clues for the Study of Evolution of Animal Parasites. November-December 1996


INHS Annelid Collection

18 June 2002 cam



Illinois Natural History Survey

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