Relevant Synonyms Tapes quadriradiatus Deshayes, 1853 Tapes semidecussatus Reeve, 1864 Tapes violascens Deshayes, 1853 Tapes philippinarum (Adams and Reeve, 1850) Misidentification -  photo: L. Mizzan

SHORT DESCRIPTION Shell large, solid, equivalve, inequilateral. Outline almost rectangular, longer than high. Beaks at the anterior 1/3, pointing towards the front. Coarse sculpture of numerous radial and concentric striae which become nodulose at the point of intersection; radial ribs slightly more prominient than concentric ones. Lunule narrowly heart shaped. Pallial sinus heel-shaped. Internal margin smooth. color : extremely variable in color and pattern. Exterior generally cream, variously rayed, banded or blotched with brown. Interior white to pinkish-white; within the pallial line flushed with pale yellow. common size : shell 25-57 mm in length. Commercial size ca 40 mm. DISTINGUISHING CHARACTERISTICS Similar to the native Tapes decussatus (Linnaeus, 1758) from which it is distinguished by the much more pronounced decussate sculpture, the more angulated shell both posteriorly and anteriorly and the almost fused siphons. BIOLOGY / ECOLOGY Studies carried out in Thau/France and Venice (Italy) lagoons revealed that the best growth period is during phytoplankton bloom (spring and autumn) at temperatures between 10 and 20°C and the reproduction period extends from May to October (Maitre-Alain, 1983, 1985). habitat : brackish waters species. Burrows in sand or muddy-gravel bottoms below the mid tide level to a few meters deep, usually in quiet waters. From the intertidal zone to 4 m deep.

1st Mediterranean record Languedoc, France, 1981 [1980]. DISTRIBUTION Worldwide: original distribution in Japan; introduced for marine farming on the Atlantic coast of France where it has become established in the wild since the 1980's. Mediterranean: introduced first in 1980 in France (Bodoy et al., 1981); in 1983 in the Venice lagoons for experimental aquaculture (Cesari and Pellizzato, 1985; Breber, 1985 as Tapes semidecussatus): now found on the coasts of Romagna and Sardinia. A recent record in the Turkish North Aegean Sea, difficult to explain, is until further evidence considered accidental (Albayrak et al., 2001). ESTABLISHMENT SUCCESS Well established; acclimatized and rapidly spread, forming natural populations (Lazzari and Rinaldi, 1994), with densities >1000 ind./m² (Breber, 2002) occasionally limiting or even replacing the native Tapes decussatus. speculated reasons for success : favourable conditions for larval dispersal and settlement (Lazzari and Rinaldi, 1994). MODE OF INTRODUCTION Intentionally; rapidly expanded outside the farming areas. IMPORTANCE TO HUMANS Edible. Clam farming.

KEY REFERENCES Bodoy A., Maître-Allain T. and Riva A., 1981. Croissance comparée de la palourde européenne Ruditapes decussatus et de la palourde japonaise Ruditapes philippinarum dans un écosystème artificiel méditerranéen. Vie marine, 2: 39-51. Breber P., 2002. Introduction and acclimatisation of the Pacific carpet clam, Tapes philippinarum, to Italian waters. Pp. 120-126. In: E. Leppäkoski et al. (eds.), Invasive aquatic species of Europe: distributions, impacts and management. Kluwer, Dordrecht. Cesari P. and Pellizzato M., 1985b. Molluschi pervenuti in Laguna di Venezia per apporti volontari o casuali. Acclimazione di Saccostrea commercialis (Iredale and Roughely, 1933) e di Tapes philippinarum (Adams and Reeve, 1850). Bollettino Malacologico, 21(10-12): 237-274.   Maitre-Allain Thierry, 1985. Données sur la reproduction de la palourde Japonaise Ruditapes philippinarum dans l'étang de Thau (Hérault, France). Rapport et Procès-verbaux des Réunions, CIESM, 29(4): 109-110. Mizzan L., 1999. Le species alloctone del macrozoobenthos della Laguna di Venezia: il punto della situazione. Bollettino del Museo Civico di Storia Naturale di Venezia, 49: 145-177. FEEDBACK / COMMENTS TO AUTHORS

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