Pacific mussel
| Pacific mussel | ||||||||||||
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Pacific mussel ( Mytilus trossulus ) |
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| Mytilus trossulus | ||||||||||||
| Gould , 1850 |
The Pacific mussel ( Mytilus trossulus ) is a type of mussel from the family of mussels (Mytilidae). It is one of the three very similar species of the Mytilus edulis group. The species status of the three species, and especially the Pacific mussel, has often been controversial, but all three Mytilus species retain their genetic identity despite occasional hybridizations between the species. The Pacific blue mussel can only be distinguished from the common blue mussel ( Mytilus edulis ) by allozyme electrophoresis and molecular biological tests . The Pacific mussel is more adapted to low salinities and is also found in the Baltic Sea. It was called there until the 1990s as the common blue mussel ( Mytilus edulis ).
features
The housing, which has the same flaps, is elongated-triangular, trapezoidal or wedge-shaped ("mytiliform"). It is very bulbous at the front and up to 10 centimeters long, in the Baltic Sea the specimens are usually much smaller. The vertebra sits at the front end. The edge of the housing with the ligament ("dorsal edge") is long and straight to slightly curved. The rear edge is initially straight to slightly curved, the rear end is more narrowly curved. The ventral margin is straight, slightly convex to slightly concave. The front end (= vertebra) is tightly curved; however, the housing does not form a "hook". The inner edge of the case is smooth. The ligament is external, but sunk, and extends over two thirds of the "dorsal margin". The lock has three small teeth that are perpendicular to the outer line. Housing shape and size are very variable and also heavily dependent on ecological factors. The two sphincters are very unequal in size. The anterior sphincter sits immediately on the anterior margin below the anterior end. It is very small and the point of attachment can only be seen indistinctly. The posterior sphincter, on the other hand, is very large and, together with the byssus retractor muscle, forms a very large, uniform muscle impression directly within the surface line.
The ornamentation on the outside of the case consists of weak concentric growth strips and slightly coarser lines that were formed during interruptions in growth. The skin is thin and brittle. The thicker outer layer of the mineral shell consists of prismatic calcite . The thinner inner layer is made up of aragonitic mother-of-pearl leaves . The thin periostracum adheres firmly to the mineral skin and does not flake off. It is blue-black to dark brown in color, and hairless.
Similar species
The Pacific blue mussel can not be distinguished from the common blue mussel ( Mytilus edulis ) on the basis of external housing features. In the White Sea , the two species are sympatric ago. Here about 80% of the specimens of the Pacific mussel have a distinct, uninterrupted dark prismatic stripe under the ligament, while 97% of the specimens of the common mussel do not have this feature. It is not known whether this characteristic can also be used in other populations in order to distinguish at least typical specimens with a high degree of probability.
The two types can otherwise only be reliably differentiated by allozyme electrophoresis (since the 1980s) and molecular biological investigations (from around 2000). Long after 1980, especially in ecological studies, no distinction was made between the two species, but Mytilus trossulus continued to be subsumed under Mytilus edulis . Therefore, the range of the two species and also the very similar Mediterranean mussel is still not known with certainty. The Pacific mussel and common mussel are believed to have separated as early as the Pliocene .
The Mediterranean mussel ( Mytilus galloprovincialis ) differs at least in the great majority of specimens by the slightly wider shell (in relation to the length), the more pointed vertebra and the clear "hook" that the pointed vertebra forms in relation to the ventral margin.
Geographical distribution and way of life
The species is mainly found on the west coast of North America, from around San Francisco to the Arctic, in the Barents Sea, on the east coast of Canada, North Greenland and in the Baltic Sea. On the west coast of North America, south of San Francisco, the range of the introduced species Mytilus galloprovincialis joins, which used to be the range of Mytilus trossulus .
Smaller populations, either through displacement or as glacial relics, exist on the west coast of Scotland ( Loch Etive ), western Norway , northern Norway, the White Sea and Iceland . In the White Sea the common blue mussel ( Mytilus edulis ) and the Pacific mussel occur together ( sympatric ). However, they are mostly ecologically separated there. The Pacific mussel is more common in ports. Populations with hybrids are always dominated by species-specific pure-bred specimens, the hybrids only reach about 18% of the population. The Pacific mussel prefers algae substrates, while the common mussel lies more directly on the substrate.
In Scotland and also in the Baltic Sea as well as in the original range, the Pacific mussel is restricted to marine areas with rather low salinity.
Taxonomy
The taxon was introduced to scientific literature in 1850 by Augustus Addison Gould . The type material was from Killimook, Puget Sound , Oregon . The MolluscaBase lists the following synonyms : Mytilus edulis declivis Petrov, 1982, Mytilus edulis kussakini Scarlato & Starobogatov, 1979, Mytilus edulis latissimus Carpenter, 1857, Mytilus edulis normalis Carpenter, 1857, Mytilus ficus Dallouldus glomeratus , 1909 , Mytilus pedroanatus Conrad, 1855 and Mytilus septentrionalis Clessin, 1887.
According to molecular biological studies, Mytilus trossulus is not very closely related to Mytilus edulis and Mytilus galloprovincialis , but is the sister species of Mytilus californianus .
supporting documents
On-line
Individual evidence
- ↑ Fritz Gosselck, Alexander Darr, Jürgen HJ Jungbluth, Michael Zettler: Trivial names for mollusks of the sea and brackish water in Germany. Mollusca, 27 (1): 3-32, 2009 PDF
- ↑ Paul C. Dalbeck: Crystallography, stable isotope and trace element analysis of Mytilus edulis shells in the context of ontogeny. PhD thesis, University of Glasgow, 2008. Abstract
- ↑ a b Marina Katolikova, Vadim Khaitov, Risto Väinölä, Michael Gantsevich, Petr Strelkov (2016) Genetic, Ecological and Morphological Distinctness of the Blue Mussels Mytilus trossulus Gould and M. edulis L. in the White Sea. PLoS ONE 11 (4): e0152963. doi : 10.1371 / journal.pone.0152963
- ↑ Risto Väinölä, Petr Strelkov: Mytilus trossulus in Northern Europe. Marine Biology, 158 (4): 817-833, 2011. doi : 10.1007 / s00227-010-1609-z
- ^ Augustus Addison Gould: Shells of the United States Exploring Expedition. Proceedings of the Boston Society of Natural History, 3: 342-348, Boston 1851 Online at www.biodiversitylibrary.org (p. 344)
- ↑ Augustus Addison Gould: United States Exploring Expedition: During The Years 1838, 1839, 1840, 1841, 1842. Under The Command Of Charles Wilkes, Vol. 12 Atlas, Mollusca and Shells , 16 p., Sherman, Philadelphia 1856 Online at www .biodiversitylibrary.org
- ↑ MolluscaBase: Mytilus trossulus Gould, 1850
- ↑ Daniel García-Souto, Auriel Sumner-Hempel, Susana Fervenza, Concepción Pérez-García, Angel Torreiro, Rodrigo González-Romero, José M. Eirín-López, Paloma Morán, Juan J. Pasantes: Detection of invasive and cryptic species in marine mussels (Bivalvia, Mytilidae): A chromosomal perspective. Journal for Nature Conservation, 39: 58-67, 2017 doi : 10.1016 / j.jnc.2017.07.005