Dwarf heather snail
| Dwarf heather snail | ||||||||||||
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Dwarf heather snail ( Xerocrassa geyeri ) |
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| Scientific name | ||||||||||||
| Xerocrassa geyeri | ||||||||||||
| ( Soós , 1926) |
The dwarf heather snail ( Xerocrassa geyeri ) is a species of snail from the Geomitridae family in the order of the pulmonate snail (Pulmonata).
features
The spherical, slightly pressed cases are 3.5 to 5 mm high and 5 to 8 mm wide. The protoconch is about 1 mm in diameter. They have up to 4 to 4.5 whorls that are rounded on the periphery. The seams are moderately deep to shallow. The last turn does not or hardly noticeably lower towards the mouth. The mouth is rounded with sharp edges. A weak lip is rarely formed inside. The umbilicus is narrow (NW / W = 0.14) and not significantly enlarged from the last contact.
The case has a whitish shell. The surface is very coarse and irregularly ribbed. The drawing consists of mostly weak, dark brown bands, which are often interrupted and dissolved into a spiral pattern of spots. The bands or rows of spots can also be missing. Spots are often formed on the first turns, also above the periphery. The shells of the young animals are fine and hairy short.
In the female genital tract, the atrium up to the point where the arrow sacks begin is much longer than it is wide. The two arrow bags are small, only rudimentary and contain no love arrows. The glandulae mucosae are not very branched. In the male part of the genital tract, the penis is quite short, the epiphallus is about three times as long. The flagellum is also very long, about the length of the epiphallus. The penile retractor muscle starts in the lower part of the epiphallus, near the junction with the penis. The sperm library is rounded with a long stem. The penis is innervated by the right cerebral ganglion.
Similar species
The shell of the dwarf heather snail is very similar to that of the striped heather snail ( Helicopsis striata ). A reliable differentiation is only possible through an anatomical examination of the genital apparatus. The protoconch of the striped heather snail is slightly larger (1.5 mm to 1 mm), the navel is slightly wider (0.21 to 0.15). In addition, the ribs are a little more regular. In the genital apparatus of the dwarf heather snail there are only two small, rudimentary arrow sacks, which also contain no arrows. The striped heather snail has four well-formed arrow sacks, of which the outer arrow sacks also contain love arrows.
The marsh snail ( Candidula unifasciata ) also has a similar shell with a similar pattern. It is a little more conical on average. The spotted heather snail ( Candidula intersecta ), on the other hand, has a slightly more depressed shell.
Geographical distribution and habitat
The distribution area of the species extends from Spain to Central Europe. An isolated occurrence has been described from the island of Gotland. In England the species occurred after the end of the last ice age, but became extinct there early (Welter Schultes). However, the occurrences of the species are very scattered and not contiguous. In addition, a lot of evidence has to be checked, as it was often confused with the striped heather snail ( Helicopsis striata ). All evidence from Austria must be deleted, as all specimen copies for Helicopsis striata must be provided. In the French Massif Central (Causses Larzac and Bland) the dwarf heather snail occurs at 500 to 800 meters above sea level. At Mont Ventoux up to 1900 m.
The dwarf heather snail occurs only on dry lime lawns with short vegetation or on limestone rocks or limestone rubble. As a rule, it only lives in natural or very little disturbed habitats.
Way of life
The dwarf heather snail is indeed a hermaphrodite, but can only reproduce through cross fertilization; Self-fertilization is not possible.
Taxonomy
The taxon was established in 1926 by Lajos Soós as Xerophila geyeri . It is now generally assigned to the genus Xerocrassa Monterosato, 1892. In older works it can be found in the combination Trochoidea geyeri .
Danger
According to the Red List in Germany, the species is threatened with extinction. It is endangered in Switzerland (Welter Schultes). The IUCN considers the data situation to be insufficient to arrive at an assessment of the risk.
supporting documents
literature
- Rosina Fechter and Gerhard Falkner: molluscs. 287 pp., Mosaik-Verlag, Munich 1990 (Steinbach's Nature Guide 10), ISBN 3-570-03414-3 , (p. 216)
- Edmund Gittenberger: On Trochoidea geyeri (Soos, 1926) and some conchologically similar taxa (Mollusca: Gastropoda Pulmonata: Hygromiidae). Zoological Mededelingen Leiden, 67 (19): 303-320, Leiden 1993 PDF
- 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. 251)
- 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
On-line
Individual evidence
- ^ A b Bernhard Hausdorf, Jan Sauer: Revision of the Helicellinae of Crete (Gastropoda: Hygromiidae). Zoological Journal of the Linnean Society, 157: 373-419, 2009 doi : 10.1111 / j.1096-3642.2008.00504.x
- ↑ Willy De Mattia, Barna Páll-Gergely: Records of Xerocrassa muehlfeldtiana (Rossmässler 1837) refer to X. rhabdota (Sturany 1901): Redescription of the species and detailed anatomical description of other Xerocrassa species (Gastropoda; Pulmonata; Hygromiidae). Journal of Conchology, 41 (6): 1-12, 2014 PDF .
- ↑ Alexander Reischütz, Peter L. Reischütz: Red List of Molluscs (Mollusca) Austria. In: Klaus Peter Zulka (ed.): Red lists of endangered animals in Austria: reptiles, amphibians, fish, moths, mollusks. Pp. 363-434, Böhlau-Verlag, Vienna 2007 ISBN 978-3-205-77478-5 (p. 410).
- ↑ PDF ( Memento from March 4, 2016 in the Internet Archive )
- ^ Frédéric Magnin: Competition between two land gastropods along altitudinal gradients in south-eastern France: neontological and palaeontological evidence. Journal of Molluscan Studies, 59: 445-454, 1993 doi : 10.1093 / mollus / 59.4.445
- ↑ Lajos Soós: A new Xerophila from Germany, Xer. geyeri, and anatomical remarks on Xer. barcinonensis (Bgt.). Archives for Molluscology, 58 (2): 96-106, Frankfurt / M., 1926.
- ↑ Fauna Europaea: Xerocrassa geyeri (Soos 1926)
- ^ Vollrath Wiese: The land snails of Germany. 352 p., Quelle & Meyer, Wiebelsheim 2014 ISBN 978-3-494-01551-4 (p. 273)
- ↑ Falkner, G., Falkner, M. & von Proschwitz, T. 2013. Xerocrassa geyeri. The IUCN Red List of Threatened Species 2013: e.T156798A4999174. doi : 10.2305 / IUCN.UK.2011-1.RLTS.T156798A4999174.en .
