The string worms (Nematomorpha) are an animal trunk of the (Ecdysozoa). Their scientific name is derived from the Greek nematos, "thread "and morphe, "shape ". More than 320 kinds of this group live particularly in the fresh water, some occur however also in the sea. The white to black, sometimes also brownishly to reddish colored worms are usually very long and extremely thin; extreme lengths can be achieved by up to two meters as with Gordius fulgur; the animals are broad thereby however only maximally three millimeters.
The youth forms of the string worms are parasitisch. They possess a drilling apparatus, with which they know itself into the landlord (usually an insect) installation ears. The adults of animals abandoned only to the oviposition the landlord and can be particularly found at this time as worm balls at brooks.
The string worms belong to the groups of animals, which were ignored as far as possible in the research so far. According to few is well-known over this group of animals compared with other Taxa. The first clear mention found a string worm in the Historia Animalium (1551-1587) of Conrad Gesner. It called the string worms after their popular name in this work as a water calf or on latin Vitulus aquaticus. At this time the typical two-piece naming was however not yet developed, this taken place in the well-known 10. Edition of the Systema Naturae of Carl von 1758. Within the worms it arranges here also an animal with the name Gordius aquaticus, designated after the Gordi knot. It referred thereby to a quotation of Aldrovandus, that at the beginning 17. Century a ball of worms with the famous knot of the Greek mythology compared.
In the future Gordius were assigned to the kind both free-living string worms and parasitische forms of the insects, the latters became 1788 of the free-living Gordius kinds as Filaria abgespalten. Only by a set of new observations it could be however clarified that the Intestinalfilarien was identical to the free-living worms. So for instance F could observe. Dujardin 1842, how a string worm from an insect changed into the free water. It called this again discovered animal Mermis and cleared up that at least with this worm a parasitische and a free-living development phase exist. The fact that the Mermis did not belong however into the relationship of the Gordius kinds was at that time still unknown, only 1886 it to the thread worms (today in the family of the Mermithidae) was placed. 1849 and 1851 could be discovered by E. pit and J. Leidy also the morphologically deviating larvae of the string worms. Also the first contributions were published about at the same time over the internal anatomy of the animals (F. Dujardin 1842, A.A. Berthold 1843, G. Meissner 1856).
1847 described Creplin a second kind of the string worms, which he called Chordodes; A.E. Verrill (1879) described a sea-living string worm, which got the name Nectonema agile from it as the first. These sea string worms were combined 1887 by F. Vejdovsky with "the Gordiacea "into the Nematomorpha. To the end 19. Century were added a number of new kinds, which were found particularly by the expeditions into different continents. Camerano, one of the most successful editors of the group, introduced according to 1897 with Parachordodes and Paragordius two new kinds, all further Gattungsbezeichnungen came in the course 20. Century in addition.
The more exact knowledge of the anatomy of the animals took place only in the second half 20. Century, in which different string worms were examined histologically and with the help of the transmission electron microscopy (TEM). The raster electron microscopy (REM) became particularly for the identification and determination of the animals an indispensable tool. Among the most well-known Nematomorphenforschern of the today's time for instance Andreas Schmidt Rhaesa, which would like to clear above all the evolutiven connections up within the string worms, as well as Ben Hanelt (Lincoln, the USA), active in Bielefeld, ranks, Fred Thomas (Montpellier, France) and Cristina de Vilalobros (La Plata, Argentina)
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