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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 6676

Henriette Herlant-Meewis; [Enkystement chez les Oligochetes Aeolosomatidae]. Revue Canadienne de Biologie 9:429-455, 1951

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The fresh-water Oligochaeta worms belonging to the family of Aeolosomatidae, Aeolosoma hemprichi and Aeolosoma variegatum are enable of encystment. This phenomenon takes place in nature in Canada at the beginning of Winter, it enables the animal to withstand the cold: it is an hibernation process and not a rest phase succeeding an intense sexual or asexual activity. Experimentally, the encystment can be induced by submitting particularly well fed worms to a temperature of about 6 degrees C. The zoids of the chains can then be observed to separate themselves rapidly; these chains remaining short and consisting only two individuals. Concurrently the worm's movements show down and they change their appearance, becoming opaque while refringent granules appear in their coeloma. During this period they are building up reserves. They then rotate upon themselves, meanwhile abundantly excreting mucus. This mucus hardens progressively and produces a transparent cyst, inprisoning the animal which more or less comes to rest, this depending on the species. If the cysts are placed at a temperature of 20 degrees C, the worm's movements become more active, at the same time their reserves are used up and they become more transparent. At a certain movement the cyst ruptures freeing the worm which immediatly proceeds to grow according to the laws of scissiparity typical of the species.