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''Heligmosomoides polygyrus'' (formerly known as ''Nematospiroides dubius'') is a common parasitic nematode found in the duodenum and small intestine of woodmice and other rodents. They are 5-20 mm in length and bright red due to the pigmentation of their tissues. They are usually heavily coiled, with the female having 12-15 coils and the male 8-12. The male can be distinguished from the female by a prominent copulatory bursa and two long, thin spicules at the posterior end. These worms often form cysts in the wall of the intestine. These cysts often become infected with bacteria, but it is not yet known if these are harmful to the host. This organism is often used to model human helminth infection in laboratory mice. == Life cycle == Heligmosomoides polygyrus has a direct life cycle. its life cycle began with the eggs that get out with the faeces of suitable host into the environment. After two days they hatch as larvae which size is about 300 μm in length. The larvae moult 3 days later but it retain the shed cuticle layer for protection. It is at this point they become infective. The larvae shed its outer protective sheath layer after they were eaten by the host. The larvae then try to penetrate the submucosa layer of the duodenum where they undergo two further moults. About seven days later the male and female adult worms emerge into the lumen of the duodenum. They attach to the epithelial layer of the duodenum where they feed on the contents of the gut. When adult worms mate, their eggs are shed in the faeces. The complete life cycle needs a minimum of 15 days, and the female worms will live inside their host for 8 months. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Heligmosomoides polygyrus」の詳細全文を読む スポンサード リンク
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