Holt, Perry C. Department of Biology, Virginia Polytechnic Institute, Blacksburg, Virginia.
Knowlton, Robert E. Department of Biological Sciences, George Washington University, Washington, DC.
Last reviewed:January 2021
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- Body form and anatomy
- Body wall
- Coelom and gut
- Nephridia and excretion
- Nervous system
- Economic importance
- Related Primary Literature
- Additional Reading
A subclass of worms, including the earthworms, within the class Clitellata of the phylum Annelida. Oligochaeta is an important annelid subclass of worms. The most notable worm types belonging to the Oligochaeta are earthworms (Fig. 1). In general, members of the Oligochaeta, commonly termed oligochaetes, exhibit both external and internal segmentation—that is, furrows in the body wall and transverse partitions (septa) dividing the coelom into chambers. In addition, oligochaetes usually possess chaetae (setae), or bristles, made of chitin, which are not borne on parapodia and are few in number (compared to members of the Polychaeta). Oligochaetes are hermaphroditic. The gonads are few in number and situated in the anterior part of the body, with the male gonads being anterior to the female gonads. The gametes are discharged through the oviducts and sperm ducts. At maturity, a portion of the oligochaete body wall is swollen into a secretory area called the clitellum. There is no larval stage during the development of oligochaetes. See also: Annelida; Polychaeta
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