ARCTIC MUSSEL

The Arctic mussel, scientifically known as “Modiolus modiolus”, stands out from other mussel species due to its remarkable size: it can grow up to 22 cm in length. It is, in fact, roughly three times longer than it is wide. Let’s explore its morphological features in detail.

Morphological features of the Arctic Mussel

The shell is equivalve, solid, and inequilateral. Large and sturdy, it has an oblong shape, not regularly triangular, with a blunt curvature located at the midpoint of the upper margin.

The outer surface of the two valves is marked by numerous concentric growth striae, irregular in pattern, and prominent ridges. The adductor muscle scars vary in size: the posterior scar is small, while the anterior scar is wide.

The shell margin is smooth, and the ligament is deeply set into a groove, extending across two-thirds of the ligamentous edge. The hinge is narrow, smooth, and lacks teeth.

The periostracum is thick, rough and often encrusted with sand grains and shell fragments. In juvenile specimens, it adheres closely and often extends into blunt spines.

As for the color:

• the external shell is typically black, but can also exhibit bluish, black-brown, or yellowish hues, (especially in adult specimens);
• the inner shell surface is whitish;
• the animal itself is dark orange, with a red foot and white shading near the thick, wrinkled base.

Arctic Mussel: distribution, ecology and habitat

The species is primarily found in the following regions:

1. Eastern Atlantic, a common species in White Sea, Faroe Islands and Iceland down to the Bay of Biscay;
2. Western Atlantic, from Labrador to North Carolina;
3. Eastern Pacific, from the Bering Sea to Monterey and Japan.

The Arctic mussel anchors itself to hard substrates and can also be found buried in soft sediments and coarse seabeds. Juvenile mussels have a low survival rate until they reach about 4 cm in length, at around 4 years of age, at which point they are less vulnerable to starfish predation.