Arcuatula perfragilis is a bivalve mollusc of the mussel family, Mytilidae, which has an Indo-Pacific distribution including the Red Sea. It has invaded the eastern Mediterranean from the Red Sea by way of the Suez Canal, a process known as Lessepsian migration.
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 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. The shell length is normally 20mm.[1]
It can be identified from Arcuatula senhousia 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.[1]
Arcuatula perfragilis has an Indo-Pacific distribution and occurs from the Red Sea east to Japan.[2] It was first recorded in the Mediterranean off Israel in 1960 but was initially misidentified as Arcuatula glaberrima (then named as Modiolus glabberrimus), it has now spread as far as Turkey.[3]
Arcuatula perfragilis is a benthic species which usually occurs in shallow water between 0-30m on intertidal mud and sand.[4]
Arcuatula perfragilis is the type species of the genus Arcuatula.