Great snail gel
| Great snail gel | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Glossiphonia complanata | ||||||||||||
| ( L. , 1758) |
The great snail leech ( Glossiphonia complanata ) is a species from the family of flat leeches (Glossiphoniidae), which mainly sucks blood from water snails , but also annelids , insect larvae , flea shrimp and water lice.
features
The cartilaginous, firm and strongly flattened body of the great snail cone is up to three centimeters long and a maximum of one centimeter wide. He has three pairs of eyes that lie one behind the other and can sometimes be partially fused together. The back is variably brownish or greenish in color and has six longitudinal ridges with yellow warts on every third ring. The front suction cup is very small compared to the rear one. In the event of danger or alarm, the animal curls up in a ball shape.
Occurrence
The habitat of the great snail cone are standing and flowing waters of all kinds. It can usually be found under stones or on water plants. The distribution area of the ubiquitous species includes Europe, Asia and North America. The saprobic index for this species is 2.2.
Way of life
The large snail leech mainly sucks on snails and worms, including the water snails Potamopyrgus antipodarum and Radix peregra as well as little bristles of the genus Tubifex . Soft-skinned larvae of insects, for example mosquitoes (including mosquitoes of the genus Chironomus ) and water woodlice ( Asellus aquaticus ), are also used less often for nutrition. The proboscis is drilled into the soft body of the prey. While insect larvae and crustaceans make up a higher proportion of the food in winter , snails and little bristles make up the majority of the prey in summer. Compared to Helobdella stagnalis , Glossiphonia complanata eats more snails and water lice , but fewer mosquito larvae. Depending on the size of the prey and the number of sucking leeches, the victim is only sucked in or completely sucked out, so that the great snail leech can be classified as both a parasite and a predator .
Snail leeches do not swim, but move forward on the ground with their two suction cups.
Development cycle
Like all leeches, the great snail leech is a hermaphrodite, in which two individuals mate with each other. Mating typically takes place in early March, with pseudospermatophores being attached to the respective sexual partner. About a week later, each partner forms 3 to 4 cocoons, in each of which 2 to 30 large, yolk-rich eggs with a transparent shell are laid. The clitellum swells immediately before the eggs are laid, while the clitellar glands form the cocoon shell in the area of the female genital opening.
The species practices brood care by the female shielding the egg cocoon attached to a base with her body and fanning it with fresh water. Unprotected eggs or cocoons are eaten by water snails. The mother animal hurls attacking snails away, which only rarely succeed in eating a mother's eggs.
A few days after oviposition, larvae about 1 mm long hatch, which take on the shape of young leeches after about a week. Immediately after hatching, the approximately 30 to 40 young attach themselves to the belly of the mother, who is only now releasing herself from the breeding site with her suckers. Another 2 to 3 weeks later, the now 2 mm long flukes leave their mother. As far as observed, their first prey is always an adult leech, for example Erpobdella octoculata , which they suckle completely as a group. Later on, however, snails predominate as a source of food. The mother does not begin to eat again until the brood care has been completed, which takes around 5 to 6 weeks from the time the eggs are laid.
In the related and often socialized small snail leech ( Alboglossiphonia heteroclita ), on the other hand, the egg cocoon is already glued to the mother's belly and carried along, so that it also eats together with the young animals during this time and later. This species is much smaller and light yellow or light gray translucent.
supporting documents
- Ulrich Kutschera : Comparative brood care behavior in leeches. In: Ulrich Kutschera: Evolutionary Biology. UTB, Verlag Eugen Ulmer, Stuttgart 2008, pp. 194–196.
- Heiko Bellmann, Klaus Hausmann, Klaus Janke, Bruno P. Kremer & Heinz Schneider: Protozoa and invertebrates. Steinbach's natural guide, Mosaik-Verlag, Munich 1991, ISBN 3-576-06495-8 ; P. 238
- Wolfgang Engelhardt: What lives in pools, brooks and ponds? Kosmos-Franckh, Stuttgart 1986 (12th edition), ISBN 3-440-05444-6 ; P. 124
- Herbert W. Ludwig: Animals and plants of our waters . BLV Verlagsgesellschaft, Munich 2003, ISBN 3-405-16487-7 ; P. 142
Web links
Individual evidence
- ↑ Meyer, Detlef .: Macroscopic biological field methods for assessing the water quality of rivers: with lists of species for beginning and experienced investigators and detailed descriptions and images of the indicator organisms . 4th, unchanged. BUND, Hannover 1990, ISBN 3-9800871-4-X .
- ↑ AJ Martin, RMH Seaby, JO Young (1994): Does body size difference in the leeches Glossiphonia complanata (L.) and Helobdella stagnalis (L.) contribute to co-existence ?. Hydrobiologia 273 (2), pp. 67-75.
- ↑ Frederick J. Wrona, Ronald W. Davies, L. Linton (1979): Analysis of the food niche of Glossiphonia complanata (Hirudinoidea: Glossiphoniidae). Canadian Journal of Zoology 57 (11), pp. 2136-2142.