Relevant Synonyms Arca amygdalum Philippi, 1847 Scapharca demiri Piani, 1981 Misidentification demiri is a replacement name for amygdalum  photo: S. Xentides / Coll. A. Zenetos

SHORT DESCRIPTION Shell solid, inequivalve, inequilateral. Outline subrectangular, longer than high. Sculpture of about 29 to 35 radial ribs, with a mean value of 33.1 ± 1.5 ribs, as broad or slighly broader than the interspaces, becoming distinctly nodulose towards the margin. Umbones at the posterior 1/3 of the length, broadly rounded with a slight depression. Upper valve (rv) larger than the lower valve (lv). Taxodont hinge in a straight line, narrower in the middle, wider at the edges. Internal ventral margin strongly crenulate. Periostracum persistent, of appressed lamellae with erect bristles. color : shell whitish with a dark brown periostracum. common size : 20-25 mm in length, 12-16 mm high. DISTINGUISHING CHARACTERISTICS The species resembles most Anadara inaequivalvis. Recent biometric analyses of the two species revealed that A. demiri has a narrower and less globose shell, but no significant difference in the number of ribs of the two species (Morello and Solustri, 2001). Juveniles of the two species are extremely similar and positive identifications should be based on adults or complete growth series. The native Anadara polii (Mayer, 1868) differs in having a more solid shell and much more convex ventral margin. BIOLOGY / ECOLOGY Seems well adapted to harbour conditions and can even prosper in heavily contaminated areas. habitat : rocky and hard substrata as well as muddy and sandy-muddy bottoms.

1st Mediterranean record Turkey, 1977 [1972]. DISTRIBUTION Worldwide: original distribution uncertain; records in the Indian Ocean. Mediterranean: recorded first in 1972 from Izmir, Turkey as Arca amygdalum (Demir, 1977); successively found in 1992 in Greece, Thessaloniki Gulf (Zenetos, 1994) and Italy, Adriatic Sea (Morello and Solustri, 2001). ESTABLISHMENT SUCCESS The species seems established but remains spotty. The Izmir population seems to be confined to the harbour and has not been reported in recent years. The Thessaloniki Gulf population is also declining as the ecosystem is becoming healthier. Abundant in north and central Adriatic with sporadic occurrence in the south Adriatic (Solustri, pers. comm.). A significant settlement of spat was found south of the Ancona area (Morello and Solustri, 2001). speculated reasons for success : possibly an opportunistic species thriving in heavily polluted ecosystems. MODE OF INTRODUCTION Unknown, probably introduced through shipping. IMPORTANCE TO HUMANS None.

KEY REFERENCES Demir M., 1977. On the presence of Arca (Scapharca) amygdalum Philippi, 1847 in the harbour of Izmir, Turkey. Istanbul Universitesi Fen Fakultesi Mecmuasi Sér. B, 42: 197-202, 1 pl. Morello E. and Solustri C., 2001. First record of Anadara demiri (Piani, 1981) (Bivalvia: Arcidae) in Italian waters. Bollettino Malacologico, 37(9-12): 231-234. Piani P., 1981. Scarpharca demiri nomen nuovum pro Arca amygdalum Philippi. Bollettino Malacologico, 17(11-12): 284.   Zenetos A., 1994. Scapharca demiri (Piani, 1981): First finding in the North Aegean Sea. La Conchiglia, 271: 37-38. FEEDBACK / COMMENTS TO AUTHORS

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