The Spiny Fan-Mussel, also known as the Rough Penshell, is a species in the class of the Bivalvia and thus belongs to the phylum of the Mollusca. Pinna rudis was first described in 1758 by Linnaeus.
Description
The Spiny Fan-Mussel has a wedge-shaped housing. That means towards the the foot it is pointed. The colour in young specimens is orange-red to brown, while older animals are dark red. The surface of the shell is wavy, with the channels running from the foot end to the opening.
In addition, its shell is covered with small spines and is up to 3.5mm thick.
Pinna rudis has an average length of 30cm, but can reach a maximum of 56cm in length.
Habitat and Distribution
The habitat of the Spiny Fan-Mussel is varying according to different sources. Some say they live on rocky ground, while others indicate that they are rather in sandy and muddy soils. It probably lives on both. I have found them mostly on small sand surfaces in rocky reefs. You can also see them in sea grass meadows. Even if you find them more shallow, they are more common in depths between 20 and 70m. In any case, it prefers areas which are protected against water movement.
When diving in the Canaries you can observe the Spiny Fan-Mussel regularly.
In addition, its distribution area spreads in the eastern Atlantic from the Strait of Gibraltar, along the African coast, to Angola. This includes the island groups of the Azores, Madeira and St. Helena.
There are also Pinna rudis in the Mediterranean Sea and the Black Sea.
According to some sources, it also occurs in the tropical areas of the western Atlantic. However, it can easily be confused with Pinna carnea.
Biology
Pinna rudis lives sessil and is anchored with byssus threads in the ground. Its diet consists of small particles, such as plankton, which it filters out of the water.
Spiny Fan-Mussels are hermaphroditic, they produce sperm and eggs. Their larvae are planktonic and are carried away with the current until they settle at a certain, fitting site.
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