White drill shell
| White drill shell | ||||||||||||
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White borer mussel ( Barnea candida ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Barnea candida | ||||||||||||
| ( Linnaeus , 1758) |
The white borer mussel ( Barnea candida ) is a mussel from the order of the Myida that bores into the hard substrate .
features
The housing is elongated-oval in outline and up to 6 cm long. The vertebra sits in the front half of the housing. In front of and above the vertebra the edge of the case is turned outwards. The outside is concentrically ornamented with sharp ribs. The radial ribs are usually somewhat weaker than the concentric ribs. The ornamentation is particularly pronounced on the front edge of the case, which is used to drill in the sediment. At the crossing points, the ribs are drawn out like spikes or teeth. In the literature, the term " rasp teeth" is also used for this, but it should not be confused with the formations of the same name on the rasp tongue (radula) of other molluscs. A thin spoon-like structure for the attachment of the foot muscles is located on both flaps underneath the vertebra protruding into the housing. Lock and ligament are missing; therefore the valves of dead animals are almost always found individually, never in connection with the other valve. The anterior sphincter on the shell envelope at the front end of the case is long and thin. The surface line is indented very deep.
Occurrence and way of life
The white drill shell mechanically drills holes in solidified sediment and softer rocks, also in peat, less often in wood. It lives completely in these self-dug holes up to 15 cm deep; only the siphons protrude from the holes. It contributes significantly, along with other drilling mussels, to the erosion of softer sedimentary rocks under water. Since the beginning of the 20th century it has been partially displaced from these habitats by the American borer mussel ( Petricola pholadiformis ). However, it is still very common locally. It lives in small colonies at a density of up to 800 individuals per square meter. Reproduction occurs unusually in September, when water temperatures drop again. The eggs and sperm are released into the open water; fertilization is external.
distribution
The distribution area of the white borer stretches from Norway to West Africa . It occurs in the Baltic Sea to Rügen , also in the Mediterranean and the Black Sea and lives in 3 to 27 m water depth. It appears to have been taken to other regions to a small extent.
Individual evidence
- ↑ The White Shell in Thailand. ( Memento of the original from February 6, 2010 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
literature
- Dorothy Margaret Duval: Observations on the annual cycle of Barnea Candida. In: Proceedings of the Malacological Society. 35, London 1963 ISSN 0025-1194 , pp. 101-102.
- Rainer Willmann: Mussels of the North and Baltic Seas. Neumann-Neudamm, Melsungen 1989, ISBN 3-7888-0555-2 .