Noah’s Ark Shell, Arca noae

Arca Noae, also known as the Noah’s Ark shell, is a species of bivalve mollusk within the family of Arcidae. It’s found in the Mediterranean Sea along with the Adriatic Sea from low tide mark to a depth of about 200 feet.

The shell of this species grows to about 4 inches in length. It’s shortened at the anterior end and elongated at the posterior end. It is normally striped in brown and white and has fine sculptured ribs running from the umbones to the margin. The hinge is straight and long and the shell is attached very strongly to the substrate by byssal threads. There are pallial eyes on the mantle edges, especially towards the posterior end.

This species used to be common within the Adriatic, but in 1949 to 1950, there was a sudden unexplained and disastrous decline in the numbers. Since then, the populations have been creeping back up and in 2002, densities of up to 13 individuals per square meter were recorded but, due to a lack of records, it’s not clear whether a return to prior population levels had been reached.

Image Caption: Arca noae. Credit: M.Violante/Wikipedia (CC BY-SA 3.0)