Plattegel
| Plattegel | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
European flat leech ( Helobdella europaea ) with young animals |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Glossiphoniidae | ||||||||||||
| Vaillant , 1890 |
The Plattegel (Glossiphoniidae), also Knorpelegel , are a family of leeches in the order of Rüsselegel that as freshwater inhabitants live partly on the hunt for small animals, but also partly as a blood sucking ectoparasites of vertebrates . They are the only leeches that do extensive brood care .
features
At rest, the flat cones have a flat, wide body that is not clearly divided into an anterior and posterior region. The head is narrow and, with the front suction cup, is not or only barely recognizable from the body. In the middle section of the body, each of the externally not recognizable segments has 3 outer ringlets. The representatives of the genus Theromyzon ( duck leech ) have four pairs of eyes, whereas the two-eyed flat cone only has one pair of eyes, while other flat cones can have two or three pairs depending on the species. Except for Placobdella hollensis - and unlike the fish leeches - the eyes of the flat leeches are only on the head. There are also no pulsating vesicles or gills.
distribution and habitat
The flat leeches are exclusively freshwater inhabitants . They are common worldwide.
nutrition
In the family Glossiphoniidae there is next to predators such as the little Schneckenegel ( Alboglossiphonia heteroclita ), the Great Schneckenegel ( Glossiphonia complanata ) and the twin-lens Plattegel ( Helobdella stagnalis ) numerous ectoparasitic species, including the sucking in fish and frogs four-eyed Plattegel ( Hemiclepsis marginata ) , the turtle leech ( Placobdella costata ) and the duck leech ( Theromyzon tessulatum ).
Life cycle and brood care behavior
Like all other leeches, the flat leeches are also hermaphrodites , which exchange their sperm when mating or take on the role of a male and a female. While about to Entenegel ( Theromyzon tessulatum ), but also twin-lens reflex Plattegel ( Helobdella stagnalis ) embrace each other and perform a longer copulation, in which finally the sperm is exchanged, is at the Great Schneckenegel ( Glossiphonia complanata been observed), like a leech to the other - sometimes against his will - missed his sperm in one quick act. The animals lack a penis; copulation takes place with the help of spindle-shaped pseudospermatophores, which are formed by glands at the male sexual outlet and rammed through the skin of the sex partner during copulation. In the partner, the sperm leave the pseudospermatophore and swim to the egg cells to fertilize them. The deflated pseudospermatophores fall off and the wounds in the leech's skin take a few days to heal. Only in the duck leech or in the genus Theromyzon are the pseudospermatophores not pushed through the skin, but transferred into the female genital opening.
Unlike other leeches, all flat leeches practice brood care . After their eggs have been fertilized, the mated animals lay them in a cocoon over a period of several days, which, like other belt worms, is separated from the clitellum . While most leeches wipe this over the front end after egg-laying is complete, the two-eyed flat cone ( Helobdella stagnalis ) forms it in the area of the female genital opening and keeps it to itself to carry it with itself. The small snail leech ( Glossiphonia heteroclita ) does this in a similar way , while the large snail leech ( Glossiphonia complanata ) guards its immobile cocoon. Depending on the species, small leeches hatch from the cocoon after a few days, which attach themselves to the mother animal with their rear suction cup and are carried around by it. The young animals suckle the small animals captured by their mother and grow up quickly. The two-eyed platter was also observed to hand over captured Tubifex to his young . After the young animals have left their mother, they sometimes hunt prey together at first. In the case of the duck leech, on the other hand, the mother with her clinging young animals seeks out a host or allows herself to be eaten by one, so that the little ones in the bird's throat attach to the mucous membrane of the bird and have their first meal of blood.
Systematics
The families Glossiphoniidae and Piscicolidae are sister groups and together form the order of Rüsselegel (Rhynchobdellida).
The following genera belong to the Glossiphoniidae :
- Desserobdella
- Glossiphonia
- Hemiclepsis
- Placobdella
- Torix
- Actinobdella
- Alboglossiphonia
- Gloiobdella
- Haementeria
- Helobdella
- Marvinmeyeria
- Oligobdella
- Theromyzon
- Batracobdella
- Boreobdella
literature
- Hasko Nesemann, Eike Neubert: Annelida, Clitellata: Branchiobdellida, Acanthobdellea, Hirudinea. Spektrum Akademischer Verlag Heidelberg / Berlin 1999. Glossiphoniidae, p. 45.
- Glenn L. Hoffman: Parasites of North American Freshwater Fishes. University of California Press, Berkeley 1967, p. 290.
- Urania Tierreich , Volume 2. Urania-Verlag, Leipzig / Jena / Berlin 1966. P. 85, Family Glossiphoniidae, Plattegel .
- Ulrich Kutschera : Comparative brood care behavior in leeches. In: Ulrich Kutschera: Evolutionary Biology. UTB, Verlag Eugen Ulmer, Stuttgart 2008, pp. 192-200.
- Ulrich Kutschera, Peter Wirt (1986): Reproductive Behavior and Parental Care of Helobdella striata (Hirudinea, Glossiphoniidae): a Leech that Feeds its Young. Ethology 72, pp. 132-142.
- C. Wesenberg-Lund, O. Storch: Biology of freshwater animals - invertebrates. Published by Julius Springer, Vienna 1939. pp. 354–356.
Web links
- Glossiphoniidae in: Lexicon of Biology , online edition.