Arcuatula perfragilis
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.
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 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.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.