Hooked suction worms
| Hooked suction worms | ||||||||||
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Gyrodactylus salaris |
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| Scientific name | ||||||||||
| Monogenea | ||||||||||
| Carus , 1863 |
The hooked suction worms (Monogenea) are a group of primarily ectoparasitic flatworms . They are particularly common on the skin, fins and gills of fish as well as on amphibians and other vertebrates; less often they live in body cavities that are open to the outside, such as the oral cavity , the urinary bladder or in the rectum of their hosts. Very few species are true endoparasites and live, for example, in the livers of their hosts.
The group consists of about 2000 species. With Oculotrema hippopotami , only one species is known to affect mammals ; it lives in the eyes of hippos .
features
The monogenea are usually slightly flattened and, as fully grown animals, usually have a typical and conspicuous, very muscular, suction cup, which is referred to as an opisthaptor . At the front end there is also a prohaptor with up to three front suction cups in the area of the mouth opening, which is used for nutrition. The opisthaptor is developed in a species-specific manner and adapted to the host, whereby the animals are usually adapted and dependent on a very narrow host range, a single species or even on a specific body region of the host. Glue glands can exist for further attachment if the hosts have very hard skin.
Like other neodermata , hooked suction worms also have a characteristic neodermis , i.e. a secondary body covering that replaces the primary epidermis . It has characteristic folds and microvilli to enlarge the body surface.
Way of life
Hooked suction worms have a direct life cycle without a generation change and only very rarely with a change of host . Asexual reproduction does not occur in contrast to the Digenea . In those Monogenea that lay eggs , a larval stage called Oncomiracidium is responsible for host- to-host transmission . The larvae usually have cilia as cilia .
Adult hooked eye worms eat their hosts' blood , secretions and epithelial cells .
Systematics
The Monogenea are combined with the tapeworms within the Neodermata to form the Cercomeromorpha taxon . As a common and therefore characteristic feature ( autapomorphism ), the larvae in both groups have a larger number of typically shaped larval hooks ( cercomers ) on the abdomen.
The hooked suction worms are divided into two subclasses according to the complexity of the haptors: the monopisthocotylea have only one undivided opisthaptor, usually one to three attachment sclerites (hamuli) and 12 to 16 edge hooks, while polyopisthocotylea have a multi-part opisthaptor, usually with hooks. Polyopisthocotylea are almost without exception gill inhabitants and feed on blood, while Monopisthocotylea occur in the gills, skin and fins.
The Monopisthocotylea include u. a .:
- The genus Gyrodactylus , which has no eye point and is viviparous.
- The genus Dactylogyrus has four eye points and lays eggs. This is one of the largest genera of the multicellular organism with at least 970 species.
- The genus Neobenedenia . These animals are much larger than the previous ones and live on the skin of many tropical marine animals. They cause problematic diseases in aquariums .
All of the above can cause animal diseases in freshwater fish if they spread in an aquaculture .
Polyopisthocotylea are u. a .:
- The genus Diclidophora , which occurs mainly in saltwater fish, but also in some freshwater fish such as the sturgeon and the paddlefish .
- Polystoma integerrimum , a parasite found in the bladder of frogs
- Diplozoon paradoxum ( double animal ), an ectoparasite on the gills of carp-like species
supporting documents
- ↑ a b c d e Willi Xylander : Monogenea. In: W. Westheide, R. Rieger (Ed.): Special Zoology. Part 1: Protozoa and invertebrates. Gustav Fischer Verlag, Stuttgart / Jena 1996, ISBN 3-437-20515-3 , p. 243 ff.
- ↑ Willi Xylander: Cercomeromorpha. In: W. Westheide, R. Rieger (Ed.): Special Zoology. Part 1: Protozoa and invertebrates. Gustav Fischer Verlag, Stuttgart / Jena 1996, ISBN 3-437-20515-3 , p. 243 ff.
