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Pinna (bivalve)
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Pinna (bivalve)
Pinna is a genus of bivalve molluscs belonging to the family Pinnidae. The type species of the genus is Pinna rudis.
These bivalves are sessile suspension feeders that live in shallow water, fixed to the substrate with a large, silky byssus. There are 32 different species in the genus Pinna, accounting for around 40% of the diversity in the family Pinnidae, and members of the genus are present almost globally. The most extensively studied species in the genus is the critically endangered P. nobilis, a Mediterranean pen shell which was historically important as the principal source of sea silk. Members of Pinna are also valued as sources of food, pearls and for the aesthetic value of their shells.
These pen shells can reach a length of about 80–90 cm (31–35 in). They are characterized by thin, elongated, wedge-shaped, and almost triangular shells with long, toothless edges. The surface of the shells shows radial ribs over their entire length.
Pinna is distinguished from its sibling genus Atrina by the presence of a sulcus dividing the nacreous region of the valves, and the positioning of the adductor scar on the dorsal side of shells. Pinna can also be distinguished from another of its relatives Streptopinna by being larger and having a more uniform shell shape.
The internal anatomy is consistent with that of a typical mussel, and includes adductor muscles, the mantle and gut, the foot, and the byssal glands.
Pinna musculature consists of an anterior and a posterior adductor muscle, which contract to close the shell, a posterior retractor muscle for moving the foot, and dorsal and ventral pallial retractor muscles, used to connect the mantle to the edge of the shell, and pull the mantle inside the shell when necessary. With the exception of the ventral pallial retractor muscle, everything else is located on the dorsal side of the animal. The anterior adductor muscle is very small, and it is located close to the anterior point, while the posterior adductor muscle is much larger, and is located about a third of the length along the shell, near the hinge plate. The latter is attached to the valve alongside the posterior pedal retractor muscle. The foot has two parts: a more slender anterior part that projects out and a posterior part that wraps around the byssus. The byssus is composed of fibrous, iridescent, brown threads and surrounds the pair of byssal glands. The mantle is mostly translucent, except near the posterior edge, where it is spotted.
Species in the genus Pinna are geographically widespread and is known to occur in tropical and subtropical seas around the world.
Pinna species are widespread in the Indo-Pacific, ranging as far south as South Africa and New Zealand and as far north as the Persian Gulf and Japan. On the west coast of North America, Pinna members are known from North Carolina to Argentina, and are abundant in the Caribbean and Gulf of Mexico. This genus is also historically very well known from the Mediterranean and Red Seas.
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Pinna (bivalve)
Pinna is a genus of bivalve molluscs belonging to the family Pinnidae. The type species of the genus is Pinna rudis.
These bivalves are sessile suspension feeders that live in shallow water, fixed to the substrate with a large, silky byssus. There are 32 different species in the genus Pinna, accounting for around 40% of the diversity in the family Pinnidae, and members of the genus are present almost globally. The most extensively studied species in the genus is the critically endangered P. nobilis, a Mediterranean pen shell which was historically important as the principal source of sea silk. Members of Pinna are also valued as sources of food, pearls and for the aesthetic value of their shells.
These pen shells can reach a length of about 80–90 cm (31–35 in). They are characterized by thin, elongated, wedge-shaped, and almost triangular shells with long, toothless edges. The surface of the shells shows radial ribs over their entire length.
Pinna is distinguished from its sibling genus Atrina by the presence of a sulcus dividing the nacreous region of the valves, and the positioning of the adductor scar on the dorsal side of shells. Pinna can also be distinguished from another of its relatives Streptopinna by being larger and having a more uniform shell shape.
The internal anatomy is consistent with that of a typical mussel, and includes adductor muscles, the mantle and gut, the foot, and the byssal glands.
Pinna musculature consists of an anterior and a posterior adductor muscle, which contract to close the shell, a posterior retractor muscle for moving the foot, and dorsal and ventral pallial retractor muscles, used to connect the mantle to the edge of the shell, and pull the mantle inside the shell when necessary. With the exception of the ventral pallial retractor muscle, everything else is located on the dorsal side of the animal. The anterior adductor muscle is very small, and it is located close to the anterior point, while the posterior adductor muscle is much larger, and is located about a third of the length along the shell, near the hinge plate. The latter is attached to the valve alongside the posterior pedal retractor muscle. The foot has two parts: a more slender anterior part that projects out and a posterior part that wraps around the byssus. The byssus is composed of fibrous, iridescent, brown threads and surrounds the pair of byssal glands. The mantle is mostly translucent, except near the posterior edge, where it is spotted.
Species in the genus Pinna are geographically widespread and is known to occur in tropical and subtropical seas around the world.
Pinna species are widespread in the Indo-Pacific, ranging as far south as South Africa and New Zealand and as far north as the Persian Gulf and Japan. On the west coast of North America, Pinna members are known from North Carolina to Argentina, and are abundant in the Caribbean and Gulf of Mexico. This genus is also historically very well known from the Mediterranean and Red Seas.
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