Small snail gel
| Small snail gel | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Alboglossiphonia heteroclita | ||||||||||||
| ( Linnaeus , 1761) |
The small snail leech ( Alboglossiphonia heteroclita , synonym : Glossiphonia heteroclita ) is a species from the family of flat leeches (Glossiphoniidae), which sucks blood ( hemolymph ) in particular from water snails , but also worms and insect larvae .
features
The small snail leech is a soft, relatively small species of leech, it reaches a body length of a maximum of 12 millimeters. It is flattened with a rounded body contour when viewed from above, often with a slightly offset, elongated head section (front end). The front and rear suction cups are relatively small, the front edge of the front suction cup is sharp. It has three pairs of eyes that are arranged in two longitudinal rows, the first pair of eyes being closer together (generic feature). The pairs of eyes may be fused with one another or, occasionally, some may be missing. Each segment of the body consists of three rings of equal size (annuli). The female and male genital pores are fused together and open in a common pore located in the twelfth segment, in the furrow of the first or second annulus.
The animal is lively brownish translucent to yellowish in color. Usually it has a longitudinal row of dark spots (one per segment) in the middle of the body. These can merge into a dark longitudinal ligament ( forma striata ) or, not infrequently, are completely absent. The upper side of the body is smooth without warts or papillae and can be distinguished from the great snail gel.
Typically colored individuals can be distinguished from other representatives of the genus by means of the pattern. In Alboglossiphonia hyalina , the body is always monochrome and unsigned. Alboglossiphonia striata usually has a pattern of scattered, small black horizontal stripes. However, it should be noted that the color of animals preserved in alcohol fades and is then no longer recognizable. Such individuals are not always morphologically determinable down to the species.
Occurrence
The small snail gel is a Holarctic freshwater species. In the Palearctic , it is found in Central and Western Europe, north to Sweden, east to the Baltic States, in Southern Europe (Italy and the Balkans), in North Africa (Morocco), in Asia Minor and the Caucasus. Its habitat includes standing and slowly flowing water. It occurs in fresh and brackish water with a salt content of up to 3 per thousand. So it is about (together with Alboglossiphonia striata ) often in the Darß-Zingster Boddenkette .
The species lives in permanent waters of all kinds, it prefers eutrophic , warm waters, also with low oxygen content. It is very tolerant of water pollution. In rivers it occurs up to water quality class III (alpha-mesosaprob). However, it may prefer less polluted rivers than the Glossiphonia species.
In Germany the species is widespread and common from the plains to the mountains. However, the frequency has possibly been overestimated as it is very often confused with other generic representatives from which it was not always differentiated in the past.
Way of life
The small snail leech mainly sucks on snails, including those of the genus Lymnaea , on which several leeches often suckle at the same time. Smaller prey such as worms and insect larvae are also sucked out, usually completely. Therefore, the small snail leech can be classified as a predator .
Snail leeches crawl forward on the ground. They are often very agile and lively.
Development cycle
Like all leeches, the small snail leech is a hermaphrodite that lives around a year and reaches sexual maturity around April. The mutual mating takes place from May. About 25 eggs are placed in a thin-walled cocoon from which the young hatch after about 16 days at a temperature of about 14 ° C. The lesser snail leech takes care of the brood by attaching the egg cocoon to the underside of her body and carrying it around with her. In contrast to the great snail leech, it can also hunt prey during this time. The cocoon is anchored to the mother's body with cone-like extensions, on which the embryos also sit. After hatching, the young leeches attach themselves to the mother's stomach with their suction cups. Once the animal has grabbed a prey, the young animals also dig their probes into the victim and thus participate in the meal.
literature
- Jane Hatto (1968): Observations on the biology of Glossiphonia heteroclita (L.). Hydrobiologia 31 (3-4), pp. 363-384.
- Vilmut Brock, Ellen Kiel, Werner Piper: Aquatic fauna of the north German lowlands: Identification key for aquatic macroinvertebrates, with over 500 images . Blackwell Wissenschafts-Verlag, Munich 1995. pp. 45, 141
Individual evidence
- ↑ a b Hasko Nesemann, Eike Neubert: Annelida Clitellata: Branchiobedellida, Acanrhobdellida, Hirudinea. in A. Brauer (founder), edited by J. Schwoerbel, P. Zwick: Freshwater fauna of Central Europe, Volume 6 (2). Spektrum Akademischer Verlag, Heidelberg and Berlin 1999. ISBN 3 8274 0927 6 . on pages 70–73.
- ↑ Brigitta Eiseler: Identification aids for macrozoobenthos (1), taxonomy for practice. LANUV worksheet 14th published by the LANUV State Office for Nature, Environment and Consumer Protection North Rhine-Westphalia, Recklinghausen 2010, ISSN 1864-8916.
- ^ Ton van Haaren, Hans Hop, Menno Soes, David Tempelman (2004): The freshwater leeches (Hirudinea) of The Netherlands. Lauterbornia 52: 113-131.
- ↑ Uwe Jueg & Michael L. Zettner (2015): Distribution and ecology of leeches (Hirudinea) in brackish waters of the German Baltic. Ecologica Montenegrina 2 (1): 42-50.
- ↑ Nela Kubová & Jana Schenková (2014): Tolerance, optimum ranges and ecological requirements of free-living leech species (Clitellata: Hirudinida). Fundamental and Applied Limnology 185 (2): 167-180.
- ↑ Paweł Koperski (2005): Testing the suitability of leeches (Hirudinea, Clitellata) for biological assessment of lowland streams. Polish Journal of Ecology 53 (1): 65-80.
- ↑ Uwe Jueg (1998): Remarkable leeches (Hirudinea) and crab leeches (Branchiobdellida) in Mecklenburg-Western Pomerania. Lauterbornia 32: 29-47.
- ↑ Ulrich Kutschera : Comparative brood care behavior in leeches. In: Ulrich Kutschera: Evolutionary Biology. UTB, Verlag Eugen Ulmer, Stuttgart 2008, p. 198.