Septifer bilocularis (Linnaeus, 1758) MYTILIDAE Low tide, - TopicsExpress

Septifer bilocularis (Linnaeus, 1758) MYTILIDAE Low tide, Attached to rocks, South China Sea, China, 31.2mm, F++ The Ledge Mussel is an abundant mytilid widely distributed in the Indo-Pacific, ranging from Japan to Australia to Red Sea. A filter-feeding species, it lives attached to hard substrates such as rock or dead coral using byssus threads in very shallow to shallow water ranging from intertidal zone to about -15m deep. Extremely variable in colouration and pattern, the colour may be anything from black to blue to green to red. The most stunning form is possibly the almost entirely bright blue form as shown, although this colour is by no means rare in this species. The shell form, especially the convexness, is variable too and influenced by environmental factors. Individuals subjected to strong wave action generally have more convex shells than individuals in sheltered areas. Typical shell length around 40mm, although extremely large specimens may exceed 65mm.