Beer snail

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Beer snail
Beer snail (Limacus flavus)

Beer snail ( Limacus flavus )

Systematics
Class : Snails (gastropoda)
Order : Lung snails (pulmonata)
Subordination : Land snails (Stylommatophora)
Family : Schnegel (Limacidae)
Genre : Limacus
Type : Beer snail
Scientific name
Limacus flavus
( Linnaeus , 1758)

The beer snail ( Limacus flavus , Syn . : Limax flavus ) is a species of slug from the family of snails (Limacidae) in the subordination of land snails (Stylommatophora). Originally probably at home in southern Europe, the beer snail has now been transported to temperate regions by humans almost all over the world. It used to be found in damp basements and was considered a pest for storage. In the meantime the species has become rare, at least in Central Europe, and is now on the red list.

description

When fully grown, the beer snail reaches a body length of 80 to 100  mm , exceptionally up to 120 mm. The body is almost round in cross section. The keel is poorly developed. The mantle shield takes about ⅓ the length of the body. The basic color varies from dirty yellow to dark orange, but there are also yellowish green, dark red and even dark color morphs. Young animals in particular are often greenish or comparatively dark in color. In this basic color, depending on the color, there are lighter or darker, mostly elongated, irregularly arranged spots. However, no lengthways ties are formed. The stain pattern gradually disappears on the sides towards the sole of the foot. The mantle shield is the same color as the body. Occasionally the edges are colored a little more intensely. The spots are often more round and slightly denser. The wrinkles are fine and not very deep. They often match the pattern of spots. Young animals are often uniformly colored. About 22 folds can be counted on the mantle shield between the midline and the breathing hole. The breathing hole is clearly located in the back half of the mantle shield. The front and rear edges of the mantle shield are rounded. The sole is always monochrome yellowish white. The head and antennae are dark gray-blue. The body mucus is yellowish to orange in color and thin, while the mucus on the sole is colorless.

Genital apparatus of the beer stick

The hermaphroditic gland in the genital system is quite large and lobed. The hermaphroditic duct is very thin and, close to the transition to the egg ladder (spermoviduct), is strongly twisted or curled. The egg duct is comparatively short and quickly separates into (free) fallopian tubes (oviduct) and (free) sperm duct (vas deferens), which are therefore relatively long. The lower part of the fallopian tube just before it joins the atrium is strongly tubular. The bursa copulatrix does not open into the atrium, but into the lower, enlarged part of the free fallopian tube. This seminal vesicle is elongated with a short but rather thick stem. The penis is comparatively short, thick, cylindrical, less than half the length of the body and strongly folded. The rear end is usually bent forward. The comparatively weak penile retractor muscle inserts on this forward-curved part but somewhat away from the apex. The vas deferens into the penis a little closer to the apex. The spermatic duct is short, almost straight, and is connected to the penis by a membrane.

Of the three intestinal loops, the first is the longest, the third the shortest. Behind it follows the long appendix that reaches to the rear end. The chalky bowl in the coat is oval, with somewhat irregular strips of growth, and slightly asymmetrical in shape. The nucleus is shifted slightly to the left. It measures 7 to 9 mm in length and 5.5 to 6 mm in width.

Similar species

The closely related species Limax maculatus (also called L. pseudoflavus in the literature ) is usually gray in color, has darker speckles and somewhat coarser wrinkles. The antennae are gray, the body mucus is not quite as intensely yellow in color.

Geographical distribution and habitat

The original area - presumably in southern Europe - can no longer be precisely determined today. Nowadays the distribution area covers almost all of Europe, in the north to Denmark and southern Sweden due to human displacement. In the meantime it has been abducted by humans to other regions of the world, such as North and South America, Japan, Australia and even Madagascar.

The beer snail usually lives near human settlements in damp cellars (hence also called cellar snail, although this name is also used for other nudibranch species that occasionally stay in cellars), gardens, and outbuildings. In the Mediterranean area, the beer snail can also be found in well walls, damp and overgrown ruins and even outdoors. The animals hide there during the day and in dry periods in tree hollows, under dead wood or under bark.

Way of life

The animals are nocturnal and usually spend the day very hidden in sheltered places. They are often difficult to find and often only reveal themselves through dried traces of slime.

food

The food of the beer snail includes carrots, beets, potatoes, flower bulbs and similar starchy plants (parts), as well as bark and other dead vegetation, not plant parts containing chlorophyll. In feeding experiments with plant parts containing only chlorophyll (lettuce, cabbage, etc.), the animals died after a few months. Like many nudibranchs, the beer snail is attracted by the smell of beer, which is what gave it its German name. It used to be particularly common in beer cellars, where it was attracted by leaking or spilled beer. The snails often live in shafts, gullies, old houses and the like. Ä.. Because the basement and ancillary rooms are mostly in a dry and clean condition today, the beer snail is increasingly deprived of its living space. The species has become rare. In Lower Saxony the species was z. B. not found for 90 years. In October 2015, a population was discovered in Greetsiel, East Frisia. In the past few years, some new populations have been detected in the northeast. It wasn't until 2007 that a few specimens were discovered again in Einbeck . Another population was discovered in Berlin in September 2015.

In Germany, the beer snail is therefore on the Red List of Endangered Species . It can be found there in category 1 (“critically endangered”).

Reproduction and life cycle

According to Paul Hesse, the animals are sexually mature at nine to eleven months, the first egg clutches are produced between 10 and 13 months of age. The beer snails usually mate in summer, but in basement rooms with suitable temperatures all year round. Hermaphrodite ( hermaphrodite ) the pairing can be done with any other peers. It begins with another animal chasing one animal, with the chaser licking the tail tip of the chased person. The animals take on a strange body shape; it becomes fusiform and thick towards the rear. They are somewhat contracted in relation to the body shape in movement. After that, the pursued person may or may not turn right into a circle. Sometimes the successor does not respond. The bodies lie against each other with their right sides. The atria are visible as bright circles, the penes now bulge out as hemispherical cusps. The heads rise and fall, while the partners gnaw and lick each other. The necks are swollen. If the genital orifices are now placed directly next to each other, the penes turn out very quickly and wrap themselves in the process. They form a tube-like structure that is only about 1 cm long. Before the maximum protuberance is reached, the sperm packets migrate to the tips of the penes. Once they have come out and attached to the other penis, the separation of the penes is initiated and the sperm packets are visible for a brief moment. Then the separation of the animals begins and the penes are quickly drawn in. The whole copulation from the beginning of the persecution to the separation takes only seven minutes, the actual copulation only about 30 seconds. The copulation can take place on vertical as well as on horizontal surfaces. Compared to the Limax species, the beer snail shows a very simple copulation behavior , which also takes only a few minutes, in contrast to the often very complex copulation behavior of the Limax species (with foreplay, actual copulation with complicated behavior of the penes and aftermath), which usually takes much longer (up to 19 hours for Limax redii ) and always takes place on vertical surfaces or on branches at some height above the ground.

Eggs are laid two to three weeks after mating. Eggs can be laid in temperature-controlled basement rooms in all seasons. The number of eggs laid per clutch varies between one egg and 80 eggs, depending on the age and nutritional status of the animal (or 12 to 51 eggs according to Hesse). An animal can lay around 250 to 350 eggs. The eggs are elliptical with elongated mucous lobes at the poles, with which they are connected to each other in cords. Only one egg is rarely or only a few eggs are weaned, on average 20 to 50 eggs. The eggs are very variable in size; it varies from 4.2 to 4.5 × 2.5 to 2.7 mm up to 9.6 to 10.4 mm × 5.1 to 6.2 mm. The eggs are usually between 6 and 8 mm × 4 to 5 mm in size. The eggs are yellowish brown in color, but are otherwise clear as water. Only when the embryo begins to develop does the egg become somewhat cloudy. Depending on the temperature, the young hatch after 23 to 27 days, under cooler conditions between 30 and 34 days, or even 43 to 47 days, whereby not all young animals leave the egg shell at the same time, but over a period of several days.

The hatchlings are about 10 to 12 mm long and about 2 mm wide. They are initially whitish yellow with slightly darker antennae. In the course of a few days the body color changes from pale green, yellowish green to the color of adults.

In breeding experiments, the animals reached their maximum weight at 15 to 17 months, then they maintain their weight for several months with sufficient nutrition and moisture. From around 23 to 25 months the animals became senile, no longer ate regularly in spite of sufficient food supply, lost weight, often fell ill and died between 2¼ and 2½ years of age. According to Paul Hesse, the animals live to be 2½ to 3 years old and have three laying periods, according to J. and M. Szabo they even live to be four years old and lay eggs four times each time in autumn.

The egg clutch of a beer stick

Taxonomy

The taxon was set up in 1758 by Carl von Linné in the 10th edition of the Systema Natura. It is the type species of the genus Limacus Lehmann, 1864, which is understood partly as a subgenus of Limax , partly as an independent genus. In more recent works it is mostly viewed as an independent genre. The anatomy and copulation behavior are very different from the other Limax species.

literature

  • H. Kobialka, R. Kirch: On the current occurrence of Limacus flavus (Linnaeus 1758) in North Rhine-Westphalia (Gastropoda: Limacidae). In: Communications from the German Malacoological Society. Volume 67, Frankfurt / M. 2002, pp. 1-8.
  • Rosina Fechter, Gerhard Falkner: Mollusks. (= Steinbach's natural guide 10), Mosaik-Verlag, Munich 1990, ISBN 3-570-03414-3 .
  • 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. Monograph Fauny Polski, Polska Akademia Nauk Zakład Zoologii Systematycznej i Doświadczalnej, Warsaw / Kraków 1973, pp. 75–77.

Individual evidence

  1. ^ Wiktor, Andrzej, K Vardinoyannis & M. Mylonas 1994: Slugs of the Greek southern Aegean islands (Mollusca Gastropoda nuda: Milacidae, Agriolimacidae et Limacidae). Malakologische Abhandlungen, 17: 1–36, Dresden ISSN  0070-7260
  2. ↑ Smith-Ramírez, Cecilia, Juan J. Armesto, Claudio Valdovinos 2005: Historia, biodiversidad y ecología de los bosques costeros de Chile. 708 p., Universitaria, Santiago de Chile (p. 305)
  3. ↑ De Winter, AJ 1997: Limax flavus L. synanthropical in Madagascar (Gastropoda Pulmonata: Limacidae). Basteria, 61 (1-3): 40, Leiden ISSN  0005-6219
  4. ↑ a b c Frömming Ewald 1954: Biology of the Central European Landgastropods. 404 pp., Duncker & Humblot, Berlin (pp. 167-183).
  5. ↑ Limacus flavus (Linnaeus 1758) - beer snails
  6. ↑ [1]
  7. ↑ Vollrath Wiese. Land snails of Germany, Quelle & Meyer Verlag, Wiebelsheim 2014
  8. ↑ nabu.de, Bierschnegel rediscovered after 90 years , accessed on February 9, 2008
  9. ↑ Red List of Endangered Animals in Germany (BINOT et al. 1998) - Register ( Memento of the original from April 5, 2017 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.  @1@ 2Template: Webachiv / IABot / www.dessau.de
  10. ↑ a b Hesse, Paul 1926: The nudibranchs of the Palaearctic region. Treatises of the Archives for Molluskenkunde 2 (1): 1–152, Frankfurt / M.
  11. ↑ Szabo, J. & M. Szabo 1934: Lifespan and body size of some slugs. Zoologischer Anzeiger, 106: 106-111.
  12. ↑ Linnaeus, Carl. 1758: Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. S. 1824, Stockholm, Salvius. Online at GDZ (p. 652)
  13. ↑ Fauna Europaea - Limacus

Web links

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