''Arcuatula perfragilis'' is a

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

of the

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

, Mytilidae, which has an

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

distribution including the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

. It has invaded the eastern

Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...

from the Red Sea by way of the

Suez Canal The Suez Canal ( arz, قَنَاةُ ٱلسُّوَيْسِ, ') is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia. The long canal is a popular ...

, a process known as Lessepsian migration.

Description

''Arcuatula perfragilis'' has a pale green, equivalve shell with a few yellowish radial lines on the dorsal to posterior portion of the valves. The valves are typical mussel-shaped in that they are narrowly ovoid and transversely elongated. The

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

is shiny. The surface of the valve has a very weak pattern of radiating lines which is discernible only by the strong ligament along the hinge line typical of the family mytilidae. This hinge has between 1 and 5 small dysodont teeth at the anterior end with a further15 towards the posterior part beyond the

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

. The shell length is normally 20mm. It can be identified from ''

Arcuatula senhousia : ''For the Asian green mussel, see Perna viridis.'' ''Arcuatula senhousia'', commonly known as the Asian date mussel, Asian mussel or bag mussel, is a small saltwater mussel, a Marine (ocean), marine bivalve mollusk species in the family Mytilid ...

'' in the Mediterranean by its having a darker, less shiny, more rounded shell and because it possesses less distinct, fewer, smaller riblets anterior to the umbones.

Distribution

''Arcuatula perfragilis'' has an Indo-Pacific distribution and occurs from the Red Sea east to

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. It was first recorded in the Mediterranean off

Israel Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...

in 1960 but was initially misidentified as '' Arcuatula glaberrima'' (then named as ''Modiolus glabberrimus''), it has now spread as far as

Turkey Turkey ( tr, Türkiye ), officially the Republic of Türkiye ( tr, Türkiye Cumhuriyeti, links=no ), is a list of transcontinental countries, transcontinental country located mainly on the Anatolia, Anatolian Peninsula in Western Asia, with ...

Biology

''Arcuatula perfragilis'' is a benthic species which usually occurs in shallow water between 0-30m on intertidal mud and sand.

Taxonomy

''Arcuatula perfragilis'' is the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of the genus ''Arcuatula''.

References

{{Taxonbar, from=Q13392659 Mytilidae Bivalves described in 1857