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Pinctada radiata

SHORT DESCRIPTION
Shell fragile, compressed, inequivalve with the lv more inflated. Outline almost quadrate; higher than long; dorsal margin longer than body of shell; posterior margin slightly concave. Beaks pointing anteriorly. Sculpture of concentic lamellae often with rows of appressed spines. Hinge line straight. No teeth. Ligament in a single triangular depression. Spiny margins. The wide variability in shape, strength of sculpture and color accounts for the large number of synonyms.

color : externally variable, generally brownish with shades of red. Internally very pearly.

common size : usually to 50-65 mm, up to 106 mm in length.

DISTINGUISHING CHARACTERISTICS
Very similar to P. margaritifera. For diagnostic differences see P. margaritifera.

BIOLOGY / ECOLOGY
Protandric hermaphrodite species with sex inversion occurring in shells 32-57 mm. Gonad maturity is controlled by temperature (Zaouali and Zaouali, 1994). Shell morphology varies with salinity, the larger individuals occurring at lower salinity levels. Epifaunal suspension feeders.

habitat : a fouling species, lives attached by byssus to hard substrata (under stones, in crevices of rocks, algae) from very shallow the midwater depths.

1st Mediterranean record
Alexandria, Egypt, 1878 [1874].


DISTRIBUTION
Worldwide: Indo-Pacific, including throughout the Red Sea; recorded in the Suez Canal (Tillier and Bavay, 1905). Mediterranean: recorded first in 1874 as Meleagrina sp. from Egypt (Monterosato, 1878); then from Tunisia (Dautzenberg, 1895); Cyprus (Monterosato, 1899); Israel (mentioned in Monterosato, 1899); Malta (Pallary, 1912); Greece: Saronikos (Serbatis, 1963), Karpathos (Nordsieck, 1969); Lebanon (Christensen, 1972); Libya (reference in Barash and Danin, 1973); France (Zibrowius, 1979); Sicily (Di Natale, 1982); southern Turkey (Kinzelbach, 1985); Syria (Kinzelbach, 1985); W. Peloponnese (Enzenross and Enzenross, identification confirmed by A. Zenetos); Adriatic (Vio and De Min, 1996).

ESTABLISHMENT SUCCESS
Common in most places of occurrence. Accidental occurrences have been recorded in Toulon (scraped off the ship hull of a French nav ship; Zibrowius, 1979) and in Trieste (live specimens attached to an oil platform originating from the Strait of Sicily; Vio and De Min, 1996).

speculated reasons for success :
adaptated to subtropical environment; tolerance to chemical contamination.

MODE OF INTRODUCTION
 Unknown, probably both via the Suez Canal and intentionally introductions. The recent records in Greece correspond to areas where the species was intentionally introduced for marine farming (Serbetis, 1963).

IMPORTANCE TO HUMANS
Pearls. It is overcollected in search of its pearls which are of no commercial value. Used as bioindicator in polluted ecosystems.


KEY REFERENCES

  • Kinzelbach R., 1985. Lesseps'sche Wanderung: neue stationen von Muscheln (Bivalvia: Anisomyaria). Archiv fur Molluskenkunde, 115(4-6): 273-278.
  • Monterosato di T.A., 1878. Enumerazione e sinonima delle conchiglie mediterranee. Giom. Sc. Nat. ed Econ., Palermo, 13: 61-115.
  • Pallary P., 1912. Catalogue des mollusques du littoral méditerranéen de l'Egypte. Mémoires de l'Institut d'Egypte, 7: 69-207, pl. 15-18.
  • Zaouali T. and Zaouali J., 1994. Reproduction de Pinctada radiata (Leach, 1814, Mollusque, Bivalve) dans les îles Kerkennah (Tunisie). Vie Marine, Marseille, 4(1): 41-45.

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