Bavarian dwarf snail

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Bavarian dwarf snail
Sadleriana bavarica A MRKVICKA.jpg

Bavarian dwarf snail ( Sadleriana bavarica )

Systematics
Subordination : Hypsogastropoda
Partial order : Littorinimorpha
Superfamily : Littorinoidea
Family : Sea snails (Hydrobiidae)
Genre : Dwarf snails ( Sadleriana )
Type : Bavarian dwarf snail
Scientific name
Sadleriana bavarica
Boeters , 1989

The Bavarian dwarf snail ( sadleriana bavarica ) is an endemic only in Munich occurring kind of living in freshwater sadleriana .

description

External features

The Bavarian dwarf snail is only about two to four millimeters in size. It has a thick-walled, pressed, conical, brown case that measures between three to four millimeters in height and three to 3½ millimeters in width. It has 3½ to four rapidly increasing turns. The navel is open and notched. The spindle opens below the navel. It is pronounced as a periostracum-free , dense rib-striped groove. The rib strips are created by growth strips. The housings are often covered with green algae. The mouth of the housing can be closed with a lid containing chert . It is red-brown, attached to the top of the end of the foot and measures 1.1 to 1.7 millimeters.

The soft body has a black color. The sole of the foot and the base of the antennae are excluded from this. The head is clearly separated from the foot. He carries a pair of long and narrow antennae about 0.6 millimeters long. The sensors cannot be retracted. On the outside of each antennae are the bulging eyes. The snout is comparatively long, flexible and can be stretched out. The wedge-shaped widened propodium contains a pronounced propodial gland.

Mantle cavity

The mantle cavity of the Bavarian dwarf lobster covers approximately the space reaching up to half of the first turn, with an increasing narrowing towards the rear.

In the mantle cavity is located on the left side, a single-sided brushed (monopectinat) comb gills , the eight gill filaments is formed with a length of about 0.2 millimeters. In the description by Boeters, the comb gills have 15 lamellae, Koller et al. found eight lamellae in their investigations, which they attributed to intraspecific deviations. Behind the gill lies a well-developed, semicircular mantle gland. The anus opening is in the right corner of the mantle cavity. The crescent-shaped osphradium , shaped like a furrow, is ciliated. On the left side of the mantle cavity is the kidney . It measures 1.8 millimeters in length and 0.43 millimeters in width. At its back, the kidney is connected to a thin-walled pericardium that surrounds a heart with two chambers.

Digestive system

The digestive system consists of a short but wide pharynx , which is also followed by a short esophagus . It initiates in the stomach . The stomach wall is relatively thick and muscular. A well-developed midgut gland is connected to the stomach. The ciliated intestine starts at the stomach and ends on the right side of the mantle cavity. It has a single turn that is around 2½ millimeters long and 0.2 millimeters wide, relatively thick. The relatively long rasp tongue becomes about a millimeter long. It lies between two lower cartilaginous pads and a smaller upper cartilage. Their shape is similar to that of a question mark. It has about sixty rows of dark blue speckled teeth.

Reproductive organs

Bayerische dwarf snail is a single-sex nature, a feature them with other representatives of the superiority of the Caenogastropoda shares. Female and male specimens have strongly pronounced gonads after sexual maturity . They are located on the upper turns of the case.

According to Boeters' description , female representatives of the species develop a mating pouch ( Bursa copulatrix ) and two sperm storage pouches ( Receptaculum seminis ). In contrast to species of the same genus, in which the sperm storage bags are roughly the same length, Boeters emphasized the different lengths of the two sperm storage bags in the Bavarian dwarf snail.

The male reproductive organs include a gonad, a prostate and a penis . The spacious gonad is weakly twisted and overlies the midgut gland. An export channel, which is technically referred to as a gonoduct , is used to derive the sex products . In the male specimens, the thin-walled gonoduct begins with the gonads and then flows into the posterior end of the kidney-shaped, approximately 0.49 millimeter long and 0.23 millimeter wide prostate. The description of the approximately one millimeter long penis differs between the authors. Boeters indicates a smooth, flat and distally rounded penis as the result of his dissection, Koller et al. describe in their 3-D reconstruction a penis that is narrowed towards the tip and has regular folds.

distribution and habitat

Group of Bavarian dwarf snails on a stone

The endemic species has so far only been detected in a single stream in Munich. This brook feeds itself from a small groundwater source and then flows into the Isar after about three kilometers. Its water is relatively cool. In the north of Munich, the Riss glaciation left moraine hills 130,000 to 300,000 years ago . These hills were not reshaped during the subsequent Würm Cold Age by new, Würm Cold Age moraines, as was the case in nearby, comparable areas south of it. One could therefore assume that the Bavarian dwarf snail and its habitat are a relic from the Riss Ice Age.

All other species of the Sadleriana genus are native to the south of the main Alpine ridge, mainly in Slovenia and Croatia. The species could therefore also have been introduced later. According to Stresemann, this cannot yet be answered conclusively.

Sadleriana bavarica was found particularly frequently near the source at shallow water points 10 to 40 centimeters deep. During the day, she likes to linger there on stones and driftwood, which are coated with a biofilm of green algae and diatoms . Diatoms serve the kind u. a. as food. Specimens of both sexes could be observed in association with other species from the water snail family.

The Bavarian dwarf snail is considered loyal to its location. If the habitat is destroyed and due to the very limited distribution area, a new settlement of Boeters is excluded. Global warming in particular poses a threat to the occurrence , since the species is detrimental to heat and drought.

Gerhard Haszprunar , Director of the Munich State Zoological Collection, advocates keeping the exact locations of the Bavarian dwarf snail secret. Otherwise he fears clearance by collectors and dealers with commercial intentions as well as impairment of the living space by too many visitors.

Systematics and history of discovery

The Bavarian dwarf lobster ( Sadleriana bavarica Boeters ) is currently assigned to the genus Sadleriana (dwarf lobster ) Clessin , 1890 in the subfamily Horatiinae DW Taylor, 1966 within the family Hydrobiidae ( water lidded snail ) Stimpson , 1865. It was previously assigned to the subfamily Belgrandiinae de Stefani, 1877.

The snail species was discovered in the 1980s by the biologist Werner Colling and first described in 1989 by the chemist Hans D. Boeters . Originally, the species was recorded and identified by Colling in 1986 as the isolated population of Sadleriana fluminensis Küster , a species that is commonly found in the southern Alps of Slovenia . Analyzes by Boeters showed that there were differences in the housing and in the male and female genital systems. These differences could not be verified in all subsequent studies. On the basis of studies regarding the K2P distance with regard to the COI gene and the LSU-r-RNA (2004), M. Szarowska led Sadleriana bavarica and Sadleriana fluminensis as sister groups . The question of whether S. bavarica is an independent taxon or just an isolated population of S. fluminensis is controversially discussed in the specialist literature. So Koller et al. in the context of a histological and 3D microanatomical study (2014) on the assessment that this cannot (yet) be answered with certainty and that further research is needed.

The holotype is kept in the Senckenberg Nature Museum in Frankfurt am Main.

literature

  • Hans D. Boeters (1989): Unknown Western European Prosobranchia. 8. Heldia, vol. 1, pages 169/170.
  • Koller K., Brenzinger B. & Schrödl M. (2014). A caenogastropod in 3D: microanatomy of the Munich endemic springsnail Sadleriana bavarica Boeters, 1989 (Caenogastropoda, Hydrobiidae) . Spixiana. 37 (1): 1-19.

Web links

Commons : Sadleriana bavarica  - collection of images, videos and audio files

Individual evidence

  1. ↑ Thomas Anlauf: Bavarian dwarf snails - The last of their kind. Accessed on May 12, 2020 .
  2. ↑ a b c d Stresemann: Excursion fauna of Germany - Volume 1: Invertebrates without insects. Edited by Bernhard Klausnitzer. Springer Spectrum, 9th edition 2019, ISBN 978-3-662-55353-4 , doi: 10.1007 / 978-3-662-55354-1 , p. 178 f.
  3. ↑ a b c d e f g h i j k l m n o p q r Katrin Koller, Bastian Brenzinger, Michael Schrödl: A caenogastropod in 3D: microanatomy of the Munich endemic springsnail Sadleriana bavarica Boeters, 1989 in Spixiana 37 (1) , August 2014, pages 1-19; ISSN: 0341-8391
  4. ↑ Hans D. Boeters (1989): Unknown West European Prosobranchia. 8. Heldia 1, pp. 169/170; cited in Koller et al.
  5. ↑ Hans D. Boeters (1989): Unknown West European Prosobranchia. 8. Heldia 1, pp. 169/170., Cited in Koller et al.
  6. ^ Volker Storch, Ulrich Welsch: Kükenthal: Zoologisches Praktikum Spectrum Academic Publishing House, Heidelberg, 26th edition 2009; Pages 133f. ISBN 978-3-8274-1998-9
  7. ↑ Hans D. Boeters (1989): Unknown West European Prosobranchia. 8. Heldia 1, pp. 169/170., Cited in Koller et al.
  8. ↑ The Bavarian dwarf snail | Video | ARD media library. Retrieved May 12, 2020 . Sabine Dobel: Two plants and one animal: these species are exclusive to Munich. In: Abendzeitung-muenchen.de . April 19, 2020, accessed May 12, 2020 .
  9. ↑ a b Münchner Schnecke, Münchner Primel - Exclusive life in the city. In: Bayerische Staatszeitung . April 20, 2020, accessed May 12, 2020 .
  10. ↑ a b Hans D. Boeters: One snail - two discoverers. In: sueddeutsche.de. February 6, 2019, accessed on July 6, 2020 (letter to the editor on the article The last of their kind from January 16, 2019).
  11. ↑ Katrin Blawat: Researchers call for the locations of rare species to be kept secret. In: sueddeutsche.de . July 12, 2017, accessed May 25, 2020 .
  12. ^ MolluscaBase: Sadleriana bavarica Boeters, 1989
  13. ↑ Diana Delicado: A rare case of stygophily in the Hydrobiidae (Gastropoda: Sadleriana) in Journal of Molluscan Studies, Volume 84-4, November 2018, pages 480-485, doi: 10.1093 / mollus / eyy032
  14. ↑ M. Szarowska: sadleriana pannonica (Frauenfeld, 1865): A lithoglyphid, or hydrobiid amnicolid taxon? in Journal Molluscan Studies 2004, 70 (1), pages 49-57; doi : 10.1093 / mollus / 70.1.49