Arch ( lat. Arca ) - a genus of bivalve mollusks with a number of morphophysiological features that distinguish it from the rest of the class. They live in the seas and oceans , for example, the North [2] , Mediterranean and Adriatic seas , in the Atlantic Ocean [3] [4] (the maximum known depth is 3696 m [5] ). Commercial mollusks are used as food [6] [4] .
| Arch |
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| Scientific classification |
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| No rank : | Bilateral symmetrical |
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| International scientific name |
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Arca Linnaeus , 1758 |
| Synonyms |
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- according to WoRMS [1] :
- Byssoarca Swainson, 1833
- Cibota Mörch, 1853
- Daphnoderma Poli, 1795
- Navicula Blainville, 1825
- Tetrarca F. Nordsieck, 1969
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Content
The shell is elongated, mostly trapezoidal, angular in shape, with the crown shifted forward. Valves equal. Between the crown and the upper edge there is a ligamentous area (area). There are grooves (chevrons) on it, which are traces of the attachment of a ligament that moves as the shell grows. The upper edge of the sash is straight, long. The castle and gills retain a primitive structure [7] . Taxodont type lock: with numerous vertical or weakly cut small teeth. There are 2 muscle snappers. At the lower edge there is a wide bissus hole. The edges are smooth inside. A pronounced radial-ribbed relief is visible on the surface of the shell [8] , often the shell is spotty colored, which makes the mollusk invisible among underwater thickets (as, for example, in ) [9] . The foot is equipped with a suction cup for attachment [6] , but does not have a sole [10] . The edges of the mantle are not fused [11] . Gills consist of rows of thin, free, not fused strands [10] .
The internal structure of Arca has a number of primitive features. So, representatives of this genus have 2 hearts : under the intestine and above the intestine, while the rest of the mollusks have one heart, with the hind intestine passing through the ventricle . Thus, with its structure, the mollusk Arca confirms that in bivalves the heart is laid in embryogenesis as a pair on the sides of the intestine, and then these primordia are connected above and below the intestine [12] . In addition, as with all representatives of the Arka family, hemoglobin is dissolved in Arca blood, although most bivalves do not have any respiratory pigment [13] .
In the species , protandric hermaphroditism was established (first, individuals function as males, then as females) [4] .
According to the World Register of Marine Species , as of November 2016, 28 species are included in the genus, some of which have died out [1] :
- Arca acuminata Krauss, 1848
- Arca angusta Dunker, 1867
- Arca boucardi Jousseaume, 1894 - Arch of Boukard [14]
- Arca bouvieri fischer, 1874
- † Arca chambersi Beu, 1973
- † Arca cottoni Waghorn, 1926
- Arca despecta Fischer, 1876
- Arca fernandezensis Hertlein & Strong, 1943
- Arca imbricata Bruguière, 1789
- Arca kauaia (Dall, Bartsch & Rehder, 1938)
- Arca mutabilis (GB Sowerby I, 1833)
- Arca navicularis Bruguière, 1789
- Arca noae Linnaeus, 1758
- Arca ocellata Reeve, 1844
- Arca pacifica (GB Sowerby I, 1833)
- Arca patriarchalis Röding, 1798
- † Arca pittensis Marwick, 1928
- Arca rachelcarsonae Petuch & RF Myers, 2014
- † Arca subvelata Suter, 1917
- Arca tetragona Poli, 1795
- Arca truncata (GB Sowerby I, 1833)
- Arca turbatrix Oliver & Cosel, 1993
- † Arca tutamoensis (Marwick, 1931)
- Arca ventricosa Lamarck, 1819
- Arca volucris Reeve, 1844
- † Arca waitemataensis (Powell & Bartrum, 1929)
- † Arca wharekuriensis Maxwell, 1969
- Arca zebra (Swainson, 1833)
