Black snail
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Black snail ( Limax cinereoniger ) |
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| Limax cinereoniger | ||||||||||||
| Wolf in Storm , 1803 |
The black snail ( Limax cinereoniger ) is a species of nudibranch from the family of snails (Limacidae), which belongs to the land snails (Stylommatophora). With a length of up to 20 cm, some authors even give it a length of up to 30 cm, it is the largest known species of nudibranch. The taxon is somewhat problematic as some supposed synonyms have turned out to be separate species. The predominantly black basic color with lighter areas is also not very diagnostic; black species of snails occur mainly in the mountains. For this reason, the geographical distribution given in the literature over almost all of Europe is quite uncertain.
features
When fully grown, the black snail can reach a length of over 20 cm, making it one of the largest land slug species in Europe. Kerney et al. (1983) and Bogon (1990) even give lengths of up to 30 cm. Wiktor confirms in his monograph the length of up to 20 cm, but only found specimens up to 16 cm in Poland (the black snail in the photos is 16 cm long with outstretched antennae.) The body is relatively slim, the coat (shield) comparatively short; it takes up only about ¼ of the (total) body length and is mostly uniformly black in color. The keel extends from the tip of the tail to over half or the length of the body, its color is usually clearly recognizable. But there are also specimens that are completely monochrome black.
The color varies considerably and ranges from gray-brown, through blotchy-striped, black-gray to black with faint, darker longitudinal bands on each side, or a black-gray pattern of spots. Hardly any specimen in a population is exactly like another specimen. Southern European populations are a little more colorful and lighter in color. Body coloration also varies with age. Juvenile specimens are usually light, cream or brown and monochrome or only indistinctly striped. In young specimens the sole of the foot is also monochrome, in older specimens it has three rather sharply delimited longitudinal stripes, laterally each black or gray, inside light. The body and foot mucus is colorless and watery.
The feelers are also variable in color; some specimens have antennae with two dark side stripes, or the antennae are spotted. The breathing hole is in the back half of the mantle shield , which has a fingerprint-like pattern. Between the midline and the breathing hole, about 21 to 27 weak furrows are formed. As with all snails, the inside of the mantle shield contains the rudiment of the housing, a shell plate that also serves as a lime reservoir.
In the genital apparatus, the hermaphroditic gland is small and elongated. The hermaphroditic duct is almost straight in the beginning, spiraled and thickened in the end, with numerous constrictions. The coiled penis is cylindrical, about the same thickness over its entire length and up to about the length of the body. It is connected to the vas deferens almost the entire length by a thin membrane. The spermatic duct is comparatively short, runs almost straight and opens directly into the apex of the penis. The penile retractor muscle also attaches to the apex. The free fallopian tube is thinly tubular only in the upper part and abruptly thickened in the lower part. The seminal vesicle (spermathek) is elongated-pear-shaped with a short, thin stem.
Similar species
The black snail can easily be confused with the black slug ( Arion ater ). The differences are: in a black slug, the breathing hole is in the front half of the mantle shield and the foot has no keel on the back. The body shape of the black snail is significantly slimmer.
The wrinkles of the tiger's snail ( Limax maximus ) are longer and narrower, but somewhat coarser. The back keel is clearer in the Black Schnegel and the foot is three-field in the longitudinal direction. The two species also differ very clearly in their copulation behavior. In the genital system, L. maximus' penis is only about half as long.
Geographical distribution and habitat
The black snail is found in almost all of Europe with the exception of northern Scandinavia and the southern Mediterranean region. In the Alps it rises up to 2600 m (2000 m), in the Polish mountains up to 2000 m and in Romania and Bulgaria up to 2500 m. It lives in natural forests and bushland, including pure coniferous forests, and hides under stones, decomposing tree stumps, fallen tree trunks or even under loose bark. As a rule, it does not occur in commercial forests.
Way of life
The animals are nocturnal and feed on various types of fungus and algae, as well as decomposing plant material. Dead conspecifics are also eaten. To search for food they crawl on the ground, but also several meters up the trees. The animals are also active in winter when the temperatures are mild.
The mating, which lasts about an hour, usually takes place on trees from June to July. After one animal has been chased for hours by another animal, a circle is formed by the two partners at a suitable place for copulation, usually a vertical surface on a tree. The two partners crawl around in a circle, constantly licking the tips of their tails; this foreplay lasts about 15 minutes. The penis bases in the genital orifices can already be visible during the pursuit. At the latest when the circle is formed, they clearly stand out as bumps half a centimeter long. The front bodies lie against each other first. The tips of the penes, which are now about 1 cm everted, press against each other, whereby a lot of mucus is secreted. Then the front bodies lift off and the animals lick each other's front body parts. The animals then attach themselves with the tip of their tails to the surface, usually on vertical surfaces, upside down and wrap themselves screw-like. Now the body-length penes are everted out to their full length (about 10 cm). This process only takes seconds (!). The penes are now wrapped in a screw-like manner. According to some observations, this can only take place after the penes have tried several times to find each other. Once the penes have been wrapped in a screw-like manner, the end part of the penis, the cecum, is everted and the so-called penis crest unfolds, which looks like a flap and has curled edges. During this phase, the sperm package migrates to the tip of the penis. Only a few minutes after the protrusion begins, the sperm packet emerges, is captured by the comb and glued to a glandular field on the other penis. Then the reverse process takes place. The sperm packets are transferred very quickly, in five to ten seconds. Then the combs lie very close to the penes and form a pine cone shape. Then the shortening and pulling in as well as the loosening of the wrapping of the penes begins. Overall, the actual copulation only takes about 20 to 38 minutes. Then the two partners try to separate. This can take up to 20 minutes for the penes to completely separate. Overall, copulation lasts i. w. S. including prelude and epilogue according to Künkel about 73 minutes. In a few cases, after the sperm transfer, a thread of mucus forms on which the animals slide to the ground. However, it cannot be compared with the slime thread in the tiger's snail, which is formed regularly and before mating.
The animals lay several eggs, which can consist of 40 to 250 eggs (15 to a maximum of 360). In total, an individual lays 400 to 800 eggs (680 to 840 eggs) in one year. The eggs are spherical (4 to 5 mm in diameter) or slightly elongated (6 to 9 mm × 4.5 to 5.5 mm). They are deposited in the moss, not in the earth. The young hatch after 20 to 30 days (19 to 24 days). They are then usually 8 to 9 mm long and sexually mature after 1.5 to two years when they have reached a length of 160 to 190 mm. They can survive the first egg-laying period and reproduce again the following year. The black snail can live up to three years and reproduce through self-fertilization if there is no partner.
Taxonomy
The taxon was first scientifically described by Wolf in Sturm in 1803. The type locality is Oberkrumbach near Hersbruck in Middle Franconia . The independence of the species was until the beginning, z. In some cases it was even questioned until the middle of the 20th century and regarded as a synonym for Limax maximus , although Karl Künkel, with his crossbreeding attempts as early as 1916, demonstrated quite impressively that the tiger snail and the black snail are two different species. The attempts at crossing, in which one specimen each of Limax maximus and Limax cinereoniger were placed together in a terrarium, always ended with the tiger snail eating or at least eating and killing the black snail.
Danger
The species is considered potentially endangered in Upper Austria. In England, too, stocks are declining, mainly due to the current intensive forest management.
supporting documents
literature
- Klaus Bogon: Land snails biology, ecology, biotope protection. Natur Verlag, Augsburg 1990, ISBN 3-89440-002-1 .
- Rosina Fechter; Gerhard Falkner: Mollusks. (= Steinbach's nature guide. 10). Mosaik-Verlag, Munich 1990, ISBN 3-570-03414-3 .
- Ulrich Gerhardt: On the copulation of the Limacids. I. Communication. In: Journal for Morphology and Ecology of Animals. 27, Berlin 1933, pp. 401-450. doi: 10.1007 / BF00403150
- Ulrich Gerhardt: On the biology of the copulation of the Limacids. II. Communication. In: Journal for Morphology and Ecology of Animals. 28, Berlin 1934, pp. 229-258. doi: 10.1007 / BF00412991
- Michael P. Kerney, RAD Cameron, Jürgen H. Jungbluth: The land snails of Northern and Central Europe. Paul Parey, Hamburg / Berlin 1983, ISBN 3-490-17918-8 .
- Andrzej Wiktor: The Polish Nudibranchs. Translated by Alfred Borkowski. (= Monograph Fauny Polski. Volume 1). Polska Akademia Nauk Zakład Zoologii Systematycznej i Doświadczalnej, Warsaw / Kraków 1973, DNB 770325319 .
- Andrzej Wiktor: The Slugs of the Former Yugoslavia (Gastropoda terrestria nuda - Arionidae, Milacidae, Limacidae, Agriolimacidae). (= Annales Zoologici. 46). Warsaw 1996, ISBN 83-8519256-5 , p. 72.
Individual evidence
- ^ Fechter & Falkner (1990: p. 186)
- ↑ a b c Wiktor (1973: pp. 69–72)
- ↑ Kerney et al. (1983: p. 184)
- ↑ a b c d Bogon (1990: p. 228/9)
- ↑ a b c d e AnimalBase - Limax cinereoniger
- ↑ Sturm, J. 1803. Germany's fauna in illustrations based on nature with descriptions. VI. Division. The worms. 1st issue. - pp. [1], [1-32], pl. [1-16]. Nuremberg.
- ^ 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)
- ↑ 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
On-line
Web links
- Fauna Europaea
- Molluscs of Central Europe
- The Black Schnegel on http://www.schnegel.at
- The fascinating world of the Schnegel by Robert Nordsieck
- Systematic mating behavior on Wirbellose.at
Black and gray speckle pattern
Breathing hole u. Pattern coat shield
Striped sole
Egg clutches
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