Digenea
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The Digenea are a subclass of the flukes (Trematoda), which belong to the flatworm tribe . All species in this subclass have a parasitic way of life. They are endoparasites and depend on at least two hosts. The name Digenea is derived from this, which means "two generations". These parasites make a change of generation and host . Digenea includes the Sanguinicola genus ("blood worms"), which cause bloodworm disease (sanguinicolosis).
features
Digenea have a flattened and elongated shape that is typical of all flatworms.
development
Development takes place over several larval stages. First the eggs are released into watery environments where they grow into miracidium . They mature into mother sporocysts. This can lead to an invasive infestation of snails or similar intermediate hosts. In this first intermediate host they develop into daughter sporocysts or rediae . They emerge from the host and can move freely in the water as cercariae . As the second intermediate host, the fish is often infested with cercaria; there the parasites put themselves into a "waiting mode" in the form of a metacercaria . They wait until the fish is eaten by the ultimate host. Once in the final host, the worm feeds on it and is able to produce offspring. This usually happens through self-fertilization, as most Digeneas are hermaphroditic.
Systematics
Systematisation at the level of subordination has traditionally been carried out on the basis of the genesis of the excretion bladder. Then there were two superordinate orders, Anepitheliocystidia with the orders Strigeata and Echinostomida and Epitheliocystidia with the orders Plagiochiata and Opisthorchiata.
The currently most comprehensive study of phylogenetics by Olson et al. Digenea, however, divides it into two orders:
- Diplostomida Olson, Cribb, Tkach, Bray & Littlewood , 2003 - 1 subordination with 3 superfamilies.
- Plagiorchiida La Rue , 1957 - depending on the source, 10 to 13 subordinates with 19 superfamilies.
The division into three groups at the order level Strigeida, Echinostomida and Plagiorchiida is not supported by the molecular phylogenetics. Strigeida is considered a synonym of Diplostomida and Echinostomida is considered a synonym of Plagiorchiida.
swell
- Johannes Dönges: Parasitology. With special consideration of human pathogenic forms. 2nd, revised and expanded edition. Thieme, Stuttgart et al. 1988, ISBN 3-13-579902-6 .
- H. Mehlhorn and G. Piekarski: Outline of parasite science. 6th edition. Heidelberg 2002.
- Volker Storch, Ulrich Welsch: Kükenthal zoological internship. 27th edition. Springer-Verlag, Berlin / Heidelberg 2014, ISBN 978-3-642-41936-2 .
Web links
Individual evidence
- ↑ a b Heinz Mehlhorn: The Parasites of Humans: Recognize, fight and prevent diseases. Spektrum Akademischer Verlag, 7th edition 2012, ISBN 978-3827422705 , pp. 100-101.
- ^ Rüdiger Spangenberg: Sanguinicola. In: Claus Schaefer, Torsten Schröer (Hrsg.): The large lexicon of aquaristics. 2 volumes. Eugen Ulmer, Stuttgart 2004, ISBN 3-8001-7497-9 , p. 158 ( bloodworm disease ) and 869.
- ↑ a b P. D. Olson, TH Cribb, VV Tkach, RA Bray, DTJ Littlewood: Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda) In: International Journal for Parasitology 33, 2003, pp. 733-755. ( Online )
- ↑ Plagiorchiida at World Register of Marine Species (WoRMS)
- ^ A b Rafael Toledo, Bernard Fried: Digenetic Trematodes. Springer, 2nd edition 2019, ISBN 978-3030186159 , p. 26 and p. 30.