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Acta Parasitologica, Vol.46, No. 3, 2001, 151-158
Schmidt-Rhaesa Andreas - The life cycle of horsehair worms (Nematomorpha).

Zoomorphology and Systematics, Faculty of Biology, University of Bielefeld, P.O. Box 100131, 33501 Bielefeld, Germany
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The life cycle of Nematomorpha is still unknown in several respects. In general, it consists of a free-living and a parasitic phase. Reproduction and early larval development take place in the water. The larva is very small (100 Ám) and possesses hooks and stylets. It is probably passively ingested by aquatic animals, bores through the intestinal wall and encysts in different tissues. At least in representatives of the genus Chordodes development can only be completed upon the host metamorphosis into a flying insect which then has to be eaten by a praying mantid. It is not known if other nematomorph life cycles also include two hosts or the final host can be infected directly. A laboratory life cycle has been established only recently. For the marine genus Nectonema (four species), the early parasitic phase is completely unknown.

KEY WORDS: Nematomorpha, life cycle
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