Noah's Ark

• It is eaten raw on the Dalmatian coast, where it is considered a delicacy, and its outline recalls a ship's hull, which is where the name Noah's ark shell comes from.
• Unlike most bivalves, its blood contains haemoglobin, which gives its tissues a reddish colour.
• The name comes from its outline: seen edge-on, the paired shell suggests a decked boat, or Noah's ark.
• It has pallial eyes along the edge of the mantle, mostly at the rear, which detect shadows and warn it of a predator.
• It is a protandrous hermaphrodite: it matures as a male and may change sex later.
• Its shell is a remarkable material: one of the most complex and compact biomineral forms among molluscs, with little organic matrix and excellent resistance to bending and fracture.
• It was hugely abundant in the Adriatic until the Second World War. A catastrophic, unexplained collapse in 1949 and 1950, and bottom trawling afterwards, drove it down; it has recovered slowly since, and in 2002 densities of up to 13 individuals per square metre were recorded.

Skeleton type

Invertebrate - external calcareous bivalve shell (mollusc)

Habitat and environment

Rocks and boulders of the Mediterranean and the nearby Atlantic, from 0 to 60 m

Sexual maturity

Matures at two years old

Sources consulted: Wikipedia (es): Arca noae · ScienceDirect (Hughes 1989) · Science Advances, How colonial animals evolve · Wikipedia, Zooid