Theodoxus
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Common barnacle ( Theodoxus fluviatilis ) |
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| Scientific name | ||||||||||||
| Theodoxus | ||||||||||||
| Montfort , 1810 |
Theodoxus is a genus from the family of the boat snails (Neritidae), whichis also native to Europeand belongs to the parent group Neritimorpha .
features
The housings are flat and ear-shaped, the opening is flat. They are relatively small, often less than 1 cm with a few turns. The inner turns are resorbed. The animals are almost completely covered by the housing when crawling. As a rule, the cases are not ornamented. B. a bribing before. On the other hand, the housings are often quite colorful with wavy color patterns, which, however, are usually very variable internally. They have a gill and an earring on the left side . On the right side of the mantle cavity the anus and genital orifices end (in females). In males, the penis sits under the right antennae. The antennae are relatively short and pointed. The short-stalked eyes are each outside next to the antennae.
Reproduction
The species of the genus are, like all sea snails (Neritidae), of separate sexes. After fertilization, the females lay down small egg capsules that are up to 1.2 mm in diameter. The egg capsules are attached to stones and shells of conspecifics or other snails. The clutch contains up to 150 eggs. However, only one egg usually develops; the other eggs are successively eaten by the developing young animal. The other eggs thus function as food eggs. A finished young animal then hatches from the deposited egg capsule (or at most three young animals). The reproduction strategy is clearly based on quality, but this has the disadvantage that the speed of propagation in a new biotope is quite slow. Unlike other barnacles, which develop over Veliger larvae that inhabit salt water and eat plankton , the species of the genus Theodoxus are not dependent on the sea and can therefore develop completely in fresh water. That is why, in contrast to representatives of the other sea snail genera, they can also be bred in the aquarium.
Way of life and distribution
The animals live in lakes and rivers on or under stones in somewhat deeper water (mostly under 5 m). Some species also penetrate the brackish water. They are grazers who feed on green algae and diatoms , but also on detritus. However, the animals need a rough surface so that the shells of the diatoms can be rubbed against the surface and destroyed with the help of the radula . This does not work, for example, on a glass pane in the aquarium because it is too smooth. The skeletons of the diatoms cannot then be crushed and are excreted almost undigested because the animals have no jaws.
Systematics
The genus is the type genus of the subfamily Theodoxinae Bandel, 2001, which, however, was downgraded to tribe rank by Bouchet & Rocroi (2005). The systematic scope of the genus is still unclear. Some authors divide the genre into several sub-genres. Other authors, however, recognize individual (sub) genres as independent genres; other taxa are left in the status of the subgenus or are not recognized as a separate taxon at all. Fauna Europaea divides the European species into two subgenus, the nominate subgenus Theodoxus (Theodoxus) and Theodoxus (Neritaea) Roth, 1855:
- Subgenus Theodoxus (Theodoxus) Montfort, 1810
- Theodoxus baeticus (Lamarck, 1822)
- Theodoxus brauneri Lindholm, 1908
- Theodoxus cariosa Wood, 1828
- Theodoxus corona (Linnaeus, 1758)
- Danube barge snail ( Theodoxus danubialis (Pfeiffer, 1828)) (with three subspecies)
- Theodoxus elongatus (Morelet, 1845)
- Theodoxus euxinus Clessin, 1885
- Common barnacle ( Theodoxus fluviatilis Linnaeus, 1758)
- Theodoxus hispalensis by Martens, 1879
- Theodoxus jordani Sowerby, 1836
- Theodoxus karasuna Mousson, 1874
- Theodoxus meridionalis (Philippi, 1836)
- Theodoxus mutinensis (Ancona, 1869)
- Theodoxus neglectus Pease, 1861
- Theodoxus olivaceus Récluz, 1842
- Theodoxus pallasi Lindholm, 1924
- Theodoxus prevostianus (Pfeiffer, 1828)
- Theodoxus retropictus from Martens, 1879
- Theodoxus saulcyi (Bourguignat, 1852)
- Theodoxus transversalis (Pfeiffer, 1828)
- Theodoxus valentinus (Graells, 1846)
- Theodoxus velascoi (Graells, 1846)
- Theodoxus velox Anistratenko, 1999
- Theodoxus vespertinus Sowerby, 1849
- Subgenus Theodoxus (Neritaea) Roth, 1855
- Theodoxus anatolicus Récluz, 1841
- Theodoxus subterrelictus Schütt, 1963
- Theodoxus varius (Menke, 1828)
The species list was completed with the help of the websites.
literature
- Peter Glöer: The animal world of Germany. Mollusca I Freshwater gastropods of Northern and Central Europe Key to identification, way of life, distribution. 2. rework. Ed., 327 D., ConchBooks, Hackenheim 2002 ISBN 3-925919-60-0
