Bidentate leaf snail
| Bidentate leaf snail | ||||||||||||
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Bidentate leaf snail ( Perforatella bidentata ) |
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| Scientific name | ||||||||||||
| Perforatella bidentata | ||||||||||||
| ( Gmelin , 1791) |
The bidentate leaf snail ( Perforatella bidentata ) is a species of snail belonging to the family of leaf snails (Hygromiidae) from the order of land snails (Stylommatophora).
features
The spherical housing with a conical thread is 5 to 7 mm high and 6.5 to 8.5 mm wide (5 to 7 × 6.5 to 9 mm). It has seven to eight slightly arched, slowly growing turns, which are separated from each other by a shallow seam. The bottom is a little flattened. On the last turn, which only drops slightly out of the turn plane immediately in front of the mouth edge, there is a rounded bulge above the periphery. The mouth is slightly angular in cross-section, slightly flattened above and below. The mouth surface is very oblique to the coil axis. The mouth edge is curved outwards and thickened with a shiny, whitish lip. At the lower edge of the mouth there are two strong and blunt teeth (name!), A basal and a palatal tooth, which correspond to small dimples on the outside of the mouth edge. The very narrow umbilicus is almost completely covered by the bent spindle edge.
The light brown shell of the case is opaque to slightly transparent. The surface shows clear and regular growth stripes. Usually there is a white band on the periphery.
The soft body is grayish-black on the back, light on the sides and on the foot. The antennae are very long. In the male tract of the hermaphroditic genitalia, the flagellum is comparatively very long, about as long as the epiphallus. The epiphallus is somewhat longer than the penis and is only indistinctly separated from it. The penile retractor muscle attaches roughly in the middle of the epiphallus. The single arrow pouch that attaches distally to the vagina is comparatively very large. An inner arrow sack is not designed. The free discharger is comparatively long. At the junction of the spermathek or a little below there are three glandulae mucosae, which branch into up to three branches. The stem of the spermathec is very long, the bladder rests against the albumin gland. The lower (distal) part of the vagina with the attachment of the arrow sack and the lower part of the arrow sack is surrounded by a tissue cover.
Similar species
The two-toothed leaf snail differs from the toothless hair snail ( Trochulus edentulus ) by the two mouth teeth , the latter type is missing. Perforatella dibothrion has a larger shell, denser growth strips and a blunt edge on the end turn at the periphery. The single-toothed hair snail has only one tooth in the mouth.
Geographical distribution and habitat
The distribution area of the bidentate leaf snail stretches very scattered from eastern France (Vosges), over Germany, Denmark, Poland, Ukraine to western Russia. In the north it extends to southern Sweden, southern Finland and northern Russia (St. Petersburg-Novgorod region), in the south to the Alps, and further in the east to Austria and Hungary.
The two-toothed leaf snail is moisture-loving and lives on the ground in the leaf litter of moist alder forests and strips of wood along waterways or in other moist places in old forests.
Way of life
The species is comparatively insensitive to cold and is also active under the leafy layer at very low temperatures. In Poland, the breeding season lasted from May to September. Eggs were laid in the laboratory even in winter; H. the period of reproduction is controlled by external factors. The pairing takes place in the evening hours and takes about 20 minutes. In the first three to five minutes, the front part of the foot with the head and tentacles straightened up slightly. Then the two partners crawled several times in small circles (about 3 to 4 cm in diameter), which get smaller and smaller after a few minutes. After about 10 to 12 circles, both partners tilted their heads to the left. Then the two partners began to touch the edges of the feet and the now partially everted genital atria with their heads and tentacles. This mating phase lasted about 30 minutes. Then the genital atria were fully everted and the mutual transmission of the spermatophores took place. Then the genital atria were slowly withdrawn. The copulation itself lasted about 20 minutes. After copulation, the two partners remained motionless for about ten minutes before they separated.
After four weeks the eggs were laid. The fresh, milky-white eggs have a chalky shell and shine through a layer of mucus. After six to seven days they turned off-white and the surface became dull. After another eight to ten days, the shells became translucent. The eggs were slightly elliptical with a smaller diameter of 1.25 to 1.94 mm (mean: 1.49 mm, n = 84) and a larger diameter of 1.42 to 2.23 mm (mean: 1.78 mm , n = 84). The eggs were laid individually or in small clutches of 2 to 30 eggs in shady places under the leaf litter and in the ground. The young hatched after 8 to 34 days. Even within a clutch, the hatching time was very asynchronous, from one to seven days. The hatchlings had a transparent body and a transparent casing of 1.1 to 1.7 turns (mean: 1.51, n = 242). The actual, older, embryonic casing is smooth. The younger part, which is formed shortly before hatching, has peculiar, short periostracum leaflets arranged transversely to the axis of the convolutions, which are lost in later life. Apparently, self-fertilization is not possible because the few eggs that were not laid after mating did not develop. Cannibalism has not been observed in either juveniles or adults. The growth was rapid, after only 93 to 273 days the final size was reached and the inner lip was formed. About 0.7 turns were produced per month. The final size was slightly different. The young animals hatched in winter later reached their final size after 168 to 274 days (mean: 205.5, n = 20) with 6.1 to 6.3 coils. Young animals hatched in spring grew faster and after 93 to 181 days they reached 4.9 to 5.5 convolutions. The service life could not be determined with certainty in the study. The adult animals brought into the laboratory died about one year later, i. H. the animals live to be two to three years old.
In the wild, the animals are mainly found in the leaf litter and rolled up dry leaves. They also climb plants, but never higher than a few centimeters above the ground. The population density is up to 20 individuals per m². The animals are most active at night and early in the morning. The mobility is low at up to 5 meters per month, only two to three meters per month were covered.
Taxonomy
The taxon was set up by Johann Friedrich Gmelin in 1791 as Helix bidentata . It is the type species of the genus Perforatella Schlüter, 1838. The fauna Europaea only records the synonym Trochus bidens Chemnitz, 1786, an unavailable name.
Danger
The two-toothed leaf snail is classified as endangered in the Red List for Germany. On the other hand, the species is assessed as not endangered by the IUCN on the entire range.
supporting documents
literature
- Klaus Bogon: Land snails biology, ecology, biotope protection. 404 p., Natur Verlag, Augsburg 1990 ISBN 3-89440-002-1 (p. 322/3)
- Rosina Fechter and Gerhard Falkner: molluscs. 287 pp., Mosaik-Verlag, Munich 1990 (Steinbach's Nature Guide 10), ISBN 3-570-03414-3 , (p. 212)
- Michael P. Kerney, RAD Cameron & Jürgen H. Jungbluth: The land snails of Northern and Central Europe. 384 pp., Paul Parey, Hamburg & Berlin 1983, ISBN 3-490-17918-8 (p. 254)
On-line
Individual evidence
- ↑ Francisco W. Welter-Schultes: European non-marine molluscs, a guide for species identification = identification book for European land and freshwater mollusks. A1-A3 S., 679 S., Q1-Q78 S., Göttingen, Planet Poster Ed., 2012 ISBN 3-933922-75-5 , ISBN 978-3-933922-75-5 (S. 553)
- ↑ Anatolij A. Schileyko: Treatise on Recent terrestrial pulmonate molluscs, Part 14 Helicodontidae, Ciliellidae, Hygromiidae. Ruthenica, Supplement 2 (14): 1907-2047, Moscow 2006 ISSN 0136-0027 (publication date corrected in vol. 15, p. 2115) (p. 1967)
- ↑ Elżbieta Kuźnik-Kowalska, Aneta Roksela: Life cycle of Perforatella bidentata (Gmelin, 1791) (Gastropoda: Pulmonata: Helicidae). Folia Malacologica, 17 (4): 199-214, 2009 PDF .
- ^ Johann Friedrich Gmelin: Caroli a Linné, systema naturae. Tom. I. Pars VI. Pp. 3021-3910, Leipzig / Lipsiae, Beer, 1791 Online at www.biodiversitylibrary.org (p. 3642).
- ↑ Fauna Europaea: Perforatella bidentata (Schlüter 1838)
- ^ Vollrath Wiese: The land snails of Germany. 352 p., Quelle & Meyer, Wiebelsheim 2014 ISBN 978-3-494-01551-4 (p. 275)
- ↑ Falkner, G., Falkner, M. & von Proschwitz, T. 2013. Perforatella bidentata. The IUCN Red List of Threatened Species 2013: e.T156597A4970214. doi : 10.2305 / IUCN.UK.2011-1.RLTS.T156597A4970214.en . Retrieved September 28, 2015
