Relevant Synonyms Rapana thomasiana Crosse, 1861 Rapana pontica Nordsieck, 1969 Misidentification Rapana bezoar (Linnaeus, 1758) [Fischer-Piette, 1960]  photo: S. Gofas / Coll. G. Spada

SHORT DESCRIPTION Shell globose, with very large body whorl and low conical spire. Spire whorls with a strong shoulder, continued on the body whorl, and axial folds which make blunt knobs at their intersection with the shoulder; irregular spiral sculpture. Aperture large, ovate, slightly expanded, with thin outer lip with the edge fluted to match external spirals. Siphonal canal broad, widely open and bearing a series of scales. color : grey to brownish with irregular darker blotches or flames, which tend to make an interrupted pattern on the cords. Aperture orange inside. common size : specimens from the Far East up to 180 mm, Mediterranean and Black Sea specimens usually less than 120 mm. DISTINGUISHING CHARACTERISTICS This species resembles the tropical Indo-Pacific species Rapana rapiformis. It is distinguished by having a higher spire with a shoulder rather than a keel, a heavier shell with inside of aperture bright orange; juveniles of R. venosa may have the interior of the aperture more distinctly fluted, more brownish, with dark streaks along the furrows. Another Indo-Pacific species, R. bezoar, is distinguished by a more scaly sculpture overall and a white aperture. BIOLOGY / ECOLOGY Clusters of egg cases about 30 mm high are individually attached to the substrate. Larvae hatch from there after 12-17 days and remain another 14-17 days in the plankton. Adults feed on bivalves and may be scavengers on carrion. Harding and Mann (1999) reported that R. venosa can open a clam by smothering the shell and introducing the proboscis between the gaping valve, without any drilling. It has become a major pest of oyster beds in the Black Sea. Growth is rapid over the first year of life (20 to 40 mm), reproduction occurs from the second ear onwards and large specimens may be over ten years old. habitat : subtidal at 12-14 m depth (Aegean Sea); favours compact sandy bottoms, burrows almost completely, with only the siphon sticking out.

1st Mediterranean record Northern Adriatic Sea, 1974. DISTRIBUTION Worldwide: temperate Sea of Japan, Yellow Sea and East China Sea; established in the Black Sea; introduced to the western Atlantic (Chesapeake Bay and Rio de la Plata), and to Western France (Quiberon) (Mann et al., 2002). Mediterranean: recorded first in 1974 in the northern Adriatic (Ghisotti, 1974b); successively from northern Aegean Sea (Koutsoubas and Voultsiadou-Koukoura, 1991); Slovenia (De Min and Vio, 1997). A single record from Elba by Terreni (1980) without follow-up. ESTABLISHMENT SUCCESS Invasive in the northern Adriatic and the Black Sea. The occurrence in the Aegean Sea is more scanty, with only two specimens collected near natural oyster banks in the Bay of Thessaloniki. speculated reasons for success : dietary flexibility, broad ecological tolerance. MODE OF INTRODUCTION Accidental, ca. 1950 in the Black Sea, possibly independently in the Adriatic. Planktonic larvae may have arrived through ships' ballast water, but the transport of egg masses with marine farming products is more likely. IMPORTANCE TO HUMANS Active predator of epifaunal bivalves, its proliferation is a serious limitation to natural and cultivated populations of oysters and mussels. In Japan, sold as seafood on fish markets.

KEY REFERENCES Ghisotti F., 1974b. Rapana venosa (Valenciennes), nuova ospite Adriatica? Conchiglie, 10: 125-126. Koutsoubas D. and Voultsiadou-Koukoura E., 1991. The occurrence of Rapana venosa (Valenciennes, 1846) (Gastropoda, Thaididae) in the Aegean Sea. Bollettino Malacologico, 26: 201-204. Mann R., Occhipinti A. and Harding J.M., 2002. ICES special advisory report on the current status of invasions by the marine gastropod Rapana venosa. Pp. 117-134. In: ICES Report of the Working Group on Introductions and Tranfers of Marine Organisms, Gothenburg, Sweden 20-22 March 2002, Copenhagen.   FEEDBACK / COMMENTS TO AUTHORS

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