Tiger snails
| Tiger snails | ||||||||||||
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Tiger snail ( Limax maximus ) |
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| Scientific name | ||||||||||||
| Limax maximus | ||||||||||||
| Linnaeus , 1758 |
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The Limax maximus ( Latin Limax maximus ), also Big slug , great slug or Tiger slug called, is a 10 to 20 centimeter-long slug from the family of slug . It is widespread in Europe and has since been carried off almost all over the world to the moderate latitudes.
features
The tiger's nose reaches a length of up to 13 cm when stretched out, some authors even give a maximum length of up to 20 cm. It shows an irregular pattern of mostly somewhat elongated spots in the area of the coat shield on a light yellow, light brown or light gray background. With the same basic color, the spots on the body are more elongated and often arranged in rows. At the side, they can almost condense into darker bandages. The number of spots fluctuates strongly and there are also almost single-colored, spotless specimens (so-called "Varietät unicolor Heynemann ") or albinotic specimens ("Varietät candida Lessona & Pollonera "). The mantle shield takes up about a third of the body length. The rear edge is tightly rounded. A small, chalky bowl about 13 to 15 millimeters long has been preserved in the shell shield, which corresponds to the shell of the snail shell. About 21 to 26 fine furrows can be counted between the center line and the edge of the mantle shield. The sole of the foot is uniformly cream-colored. The breathing hole (pneumostom) is located on the right side a little behind the middle of the mantle shield. It is often outlined a little darker. The keel is relatively short and only takes up the last third of the back. The mucus is colorless and relatively tough.
Like all snails, the tiger snail is a hermaphrodite; each animal thus has a male and female genital tract. The hermaphroditic gland changes size and color with age and sexual activity of the animals. In younger animals it is large and brown, in older animals it is small, tongue-shaped and almost black. The long, thin hermaphrodite tunnel is strongly twisted shortly before entering the Eisamen ladder. The protein gland (albumin gland) also varies in size, depending on the age of the animals; the older the animals, the larger the gland. The egg ladder (spermoviduct) is long, thin and whitish, the penis cylindrical, about half the length of the body and strongly twisted. The spermatic duct is not twisted and is connected to the penis over most of its length by a thin membrane. The penis ends hemispherically; the end part is slightly offset by a slight constriction and slightly thickened from the insertion of the retractor muscle. The penile retractor muscle starts laterally well in front of the apex of the penis. The spermatic duct opens into the penis at about the same level as the retractor muscle, but on the other side. The seminal vesicle is small and ovoid with a short stem. The free fallopian tube is moderately long, tubular and slightly expanded just before it joins the atrium.
Geographical distribution and habitat
The species was probably originally native to southern and western Europe. In the meantime, however, it has spread throughout Central Europe - mainly through anthropogenic displacement - and is now also appearing as a neozoon in other regions of the world . In Germany it occurs in meadows , gardens and parks, but can also be found in damp cellars.
The species is also found on Ischia (Italy). The drawing of the local form there is point-like, the color is adapted to the tuff stone.
Way of life
The animals are nocturnal and hide during the day, but can also be seen during the day - especially after rain. They use piles of stones made of somewhat coarser pebbles as hiding places. Because it is damp and cool there and they are safe from their predators ( shrews , hedgehogs , etc.). They also settle in compost heaps and under piles of wood. They also retreat in piles of branches and leaves or hide under roof tiles and cavities between terrace stones. A dry stone wall also offers the beneficial organ numerous hiding places. They feed on mushrooms, withered and dead, rarely also fresh parts of plants, as well as carrion and predatory other nudibranchs. The tiger snail can overwhelm specimens that are just as big as it is. Because snails, regardless of their size, eat the eggs of other snails and their offspring, they are to be regarded as beneficials and not as pests, especially in vegetable gardens. Unfortunately, this is hardly known. At the beginning of the 20th century, the black snail ( Limax cinereoniger ) and the tiger snail ( Limax maximus ) were still considered a species by many authors. To find out whether Limax cinereoniger and Limax maximus can still mate with each other, Karl Künkel undertook breeding experiments by placing one animal of the one and the other in a terrarium. However, the attempts always ended with the tiger snail eating or at least eating the black snail. In feeding experiments, young animals that were fed only with plants containing chlorophyll perished after a few months. A group that was fed exclusively with fruit did not reach sexual maturity either. A group fed potatoes and carrots thrived best. The tiger snail never occurs in Central Europe in population sizes that noticeably damage cultivated plants.
Tiger snails are sexually mature after about 1½ to 1¾ years. Copulation begins with one animal picking up the slime trail of another specimen. Once the approaching animal has reached the other, a pursuit that sometimes lasts for hours begins, which ends with the pursued individual turning to the right at a place suitable for copulation - almost always a vertical surface - and forming a fairly regular circle with the pursuing animal. The animals move in a circle, licking each other's tails. A lot of mucus is secreted, which forms a round spot on the surface. The animals shorten and grow thicker. The front body is swollen like a spindle. The front bodies bend to the right and to the left. At the end of this part of the foreplay, the circle becomes narrower, the animals each place their heads on the partner's back. Although the genital opening is already gaping, nothing can be seen of the genitals themselves. Then the two partners begin to embrace each other stormily. They beat around violently with their front bodies, lick or gnaw each other and spread their cloak shields. During these violent movements, the animals excrete a 1½ mm thick, reddish-yellow thread of mucus with their mucous glands. After further violent movements and further mucus formation, the two partners detach themselves from the surface and hang upside down on the thread of mucus that has formed, which is twisted more and more by the violent wrapping movements and quickly becomes longer. The final length is different. Ulrich Gerhardt states 15 to 20 cm, Karl Künkel in a letter to Ulrich Gerhardt up to 43 centimeters. When the slime thread has reached its maximum length, the movements stop and the animals stretch, but intertwined and with their heads almost level. Only then do the tube-like penes, up to 4 centimeters long and 4 millimeters thick, appear in the genital orifices, which are colored bluish-white by the hemolymph. The combs can already be seen as wavy hems. The penes now begin to look for each other. To do this, the heads are lowered a little. It usually takes several attempts before the penes have found each other. They then wrap around each other. The bases of the penes remain separate. After wrapping around the penes, the combs first come into contact for a short time. The packets of seeds appear in the genital orifices and quickly slide towards the tips of the penes. The combs are now spread helically up to 2½ turns. When the two sperm packets have reached the tips of the penes, the crests of the lower 1½ turns are reattached and form a bluish ball with the penis tips. The result is the image of a hanging lamp (also called "lamp bell" in literature). The sperm packets emerge in this ball and are attached to glandular fields on the other penis. This stage remains unchanged for quite a while. After that, the separation of the penes, which emanates from the bases, begins. The combs lay against each other, detach themselves from the other penis until only the widened end pieces of the combs are connected. The penes are finally pulled apart while pulling and overcoming tough mucus. For a brief moment, the sperm packets are visible, which are now quickly everted into the penis. The penes will now be quickly and completely withdrawn into the genital opening. The wrapping around the animals now loosens. Often one animal falls to the ground while the other crawls up the slime thread and often eats it up. If a solid surface is not far, a partner tries to find a firm footing there and crawls away. Overall, the copulation from the formation of the circle to the separation usually only takes about half an hour to an hour. The actual copulation takes only 11 to 20 minutes (mean 15 minutes). Self-fertilization has also been observed, at least in captivity.
The first egg-laying takes place in July / August, the second in June / July of the following year. Two to four clutches are produced per laying period. These contain around 100 to 300 eggs, depending on the size and nutritional status of the animals. The eggs are spherical to slightly elongated; they measure 4 to 5 mm in diameter. Depending on the temperature, the development takes between 19 and 25 days, in extreme cases 45 days. However, many eggs are destroyed by parasite infestation (nematodes, mites and flies). The newly hatched young tiger snails are tiny and pale white. Only after a while, about a week later, do they get the first strips and ribbons. The tiger snail can live two and a half to three years old.
Taxonomy
The taxon Limax maximus was scientifically described as early as 1758 by Carl von Linné in the 10th edition of the Systema Naturae. It is the type species of the genus Limax . The type locality is York in England. In the past, the pre-Linnaeus name cinereus , which comes from Martin Lister , was often used in literature . The scope of the taxon or the geographical distribution in Europe has not yet been clearly clarified, as there are a number of very similar species.
Others
The tiger's knuckle was voted mollusk of the year in Germany in 2005 and in Austria for 2018/2019 .
Danger
In Schleswig-Holstein, the Great Schnegel is classified as “potentially endangered”, as is the case in Upper Austria.
Traces of grazing the green algae layer
when rappelling
Egg clutches
literature
- Klaus Bogon: Land snails: biology, ecology, biotope protection. Natur-Verlag, Augsburg 1990, ISBN 3-89440-002-1 .
- Rosina Fechter and Gerhard Falkner: molluscs. Mosaik, Munich 1990, ISBN 3-570-03414-3 (= Steinbach's natural guide , volume 10).
- Michael P. Kerney, RAD Cameron & Jürgen H. Jungbluth: The land snails of Northern and Central Europe. Parey, Hamburg / Berlin 1983, ISBN 3-490-17918-8 .
- Engelbert Kötter: Snails in a natural garden, Cadmos Verlag 2014, ISBN 978-3-840-48111-6 + e-book 3840465443
- Andrzej Wiktor: The Polish Nudibranchs. Monograph Fauny Polski, Polska Akademia Nauk Zakład Zoologii Systematycznej i Doświadczalnej, Warsaw / Kraków 1973.
- Ulrich Gerhardt (1934): On the biology of the copulation of the Limacids . II. Communication. In: Journal for Morphology and Ecology of Animals , 28: 229-258, Berlin. doi: 10.1007 / BF00412991
Web links
- Folder of the working group Mollusken NRW
- mollbase
- The mating of the tiger beaks - Robert Nordsieck
- The fascinating world of the Schnegel - Robert Nordsieck
- Molluscs of Central Europe
- The farm animal large or tiger snail (Limax maximus)
- AnimalBase - Limax maximus
Individual evidence
- ^ Fechter und Falkner (1990: p. 186)
- ↑ Kerney et al. (1983: p. 183)
- ↑ Limax gallery in alphabetical order - Clemens M. Brandstetter's website ( Memento of the original from 23 August 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ terrestrial mollusc tool - Biology and Ecology
- ↑ Engelbert Kötter: Snails in the natural garden, Cadmos Verlag 2014, ISBN 978-3-840-48111-6 e-book 3840465443
- ^ Künkel, Karl 1916: On the biology of the pulmonary snails. Results of many years of breeding and experiments. SI-XVI, 1-440, plate 1, Heidelberg, Winter Online at Biodiversity Heritage Library (p. 294)
- ^ Fromming, Ewald 1954: Biology of Central European Landgastropods. 404 pp., Duncker & Humblot, Berlin
- ↑ Gerhardt (1934: pp. 233–241)
- ↑ Lister, Martin 1678: Historiae animalium Angliae tres tractatus. 250 pp., London, Martyn.
- ↑ Mollusk of the year 2005 The tiger snail Limax maximus LINNAEUS 1758
- ^ Vollrath Wiese: Atlas of land and freshwater mollusks in Schleswig-Holstein 1991, p.141
- ↑ Seidl, Fritz 1996: The distribution of the Limacidae (Gastropoda, Pulmonata) in the district of Ried im Innkreis, Upper Austria. News sheet of the First Vorarlberg Malacological Society, 4: 27-42, Rankweil PDF
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