Pinna rudis is a bivalve belonging to the Ostreida class and within it to the Pinnidae family. It is a species that is distributed both in the waters of the Mediterranean sea, as well as in the Atlantic ocean, where we can find them in rocky bottoms between 20 to 70 meters of depth and in Posidonia oceanica meadows. It is a rather scarce species, given its density, which is approximately 0.08 individuals per 100 square meters, in other words, every 1.25 km2 we will find on average one specimen.
Pinna rudis specimens can grow up to 40-50 cm in length. Their valves are symmetrical between them and adopt an elongated triangular shape, with its widest point reaching between 15 and 20 cm. A characteristic feature of adult specimens of this species is the presence of scaly protuberances along the length and width of their valves. A multitude of organisms such as different bryozoans, ascidians and algae are frequently associated with its shell.
It is relatively easy to confuse Pinna rudis with Pinna nobilis, especially in the case of juveniles since in these stages both species have scaly protuberances on their shells. A feature that will allow us to differenciate between both speices is the envorinment in which we observe them, as Pinna rudis preffers rocky bottms, while Pinna nobilis is rarely seen on rocky bottoms. Other differential features, although somewhat more complex, is that Pinna rudis specimens have a much rougher shell with larger scaly protuberances, more separated from each other and with the edge of the valves more wavy than in the case of Pinna nobilis. The size is also slightly different, with Pinna rudis being generally smaller than Pinna nobilis. The most easily identifiable distinguishing feature is the color of the mantle, being in the case of Pinna rudis reddish with the upper edge mottled with white spots, while in the case of Pinna nobilis the mantle color is completely uniform.
The populations of Pinna rudis, unlike those of Pinna nobilis, have not been affected by the recent episodes of mass mortality observed in the waters of the Mediterranean Sea. It is estimated that a Pinna rudis can live up to 30 years of age.
The feeding of Pinna rudis is based on the filtration of the water column surrounding the specimen, to capture the organic particles present in the water.
During the summer months is when this species reproduces. Pinna rudis is a sequential protandric hermaphrodite species, that is to say they are initially males and later in life they become females. Reproduction is sexual, generating eggs and sperm that are released into the currents where fertilization occurs.
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