Pinna rudis

Pinna rudis
Pinna rudis from Sicily, on display at the Museo Civico di Storia Naturale di Milano
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Pterioida
Family:	Pinnidae
Genus:	Pinna
Species:	P. rudis
Binomial name
Pinna rudis C. Linnaeus, 1758
Synonyms
Pinna elongata P.F. Röding, 1798 Pinna ferruginea P.F. Röding, 1798 Pinna ferruginosa P.F. Röding, 1798 Pinna mucronata G.S. Poli, 1795 Pinna paulucciae A. de Rochebrune, 1883 Pinna rudis belma A. De Gregorio, 1885 Pinna rudis blama A. De Gregorio, 1885 [1][2]

Pinna rudis, the Rough pen shell or spiny fan-mussel, is a species of bivalve mollusc in the family Pinnidae. ^[3] It is the type species of the genus Pinna. This species lacks of a thorough knowledge, in the absence of specific studies and literature. ^[4]

Description

Pinna rudis has a shell that commonly reaches a length of 25–30 centimetres (9.8–11.8 in). ^{[2][4][5][6][7][8]} The roughr pen shell has a pair of very fragile, long, triangular, wedge–shaped valves, covered with large protruding scales arranged in quite regular rows. These scales are more prominent close to the opening of the shell. A half dozen low ribs radiate from the pointed end and run the length of the valves. Said valves are almost symmetrical, toothless and transparent on the ends. Their color is usually reddish brown.

The spiny fan-mussel lives with the pointed anterior end of its shell vertically anchored to rock or firm sediment by numerous byssus threads. The rear edge is rounded and free.

Pinna rudis may be confused with juveniles of Pinna nobilis, but the first species shows a more triangular and robust shell, with fewer and larger protruding scales. Moreover in P. rudis the color is more brown or pink-orange, while in juveniles P. nobilis it is homogeneously yellowish. At last the adults of P. nobilis easily exceed the size of P. rudis and totally lose the protuberances on the surface of the shell. Also the habitats of the two species are different, as P. nobilis can be found on muddy or sandy bottoms while P. rudis prefers rock crevices. ^[6][7][8]

Distribution

This species can be found in the Eastern Atlantic Ocean (Azores, Saint Helena, Morocco), in the Mediterranean (Strait of Gibraltar, Almeria, Lipari, Sicily, Tyrrhenian sea, Ionian sea), in the Black Sea and in the Caribbean waters, ranging from Gulf of Mexico, southern Florida to the West Indies and Bahamas. ^{[1][2][6][7][9]}

Habitat

This species lives in small patches of sand in rocky bottoms and in rock crevices, at depths ranging from the surface to 60 m. ^[6][7][4]

Biology

This species is a filter feeder. Water is drawn into the shell from above and passed over the ctenidium before being expelled into the open water at the exposed part of the shell. It is a hermaphrodite, the gonads producing both sperm and ova. The larvae are planktonic and drift with the currents.

References