Petricola pholadiformis

Phylum: Mollusca
Class: Pelecypoda
Order: Veneroida
Species name: Petricola pholadiformis Lamarck 1818
Synonyms: Petricolaria pholadiformis
Common name: False angel wing, American piddock
Date of introduction and origin
Petricola pholadiformis was introduced not later than 1890 (Naylor 1957) and found in the River Crouch, Essex (International Council for the Exploration of the Sea; 1972, Tebble 1976). The species is native to the USA and was introduced from there.
Method of introduction
It was an associated unintentional introduction with the American oysterCrassostrea virginica (Rosenthal 1980).
Reasons for success
Rate of spread and methods involved
Rosenthal (1980) indicates that this species has colonised several northern European countries by means of it pelagic larvae. It also possibly spread in drift wood.
It is established along south and east coasts of England from Lyme Regis, Dorset, to the Humber, Humberside (Duval 1963; J. Light & I. Killeen pers. comm.), where it is found living in clay, peat or soft rock shores. It is most common off Essex and the Thames estuary e.g. the River Medway (see Bamber 1985). European populations occur from southern Norway to the Mediterranean and Black Seas (Tebble 1976).
Factors likely to influence spread and distribution
Its spread is influenced by ocean currents as it disperses through larval transport.
Effects on the environment
In Belgium and The Netherlands it has almost completely replaced the native species Barnea candida (International Council for the Exploration of the Sea; 1972). In Britain, however, there is no documentary evidence for its having displaced native piddocks (J. Light & I. Killeen pers. comm.).
Effects on commercial interests
Control methods used and effectiveness
None used.
Beneficial effects
None known.
Petricola is remarkably similar to Barnea candida (an indigenous British species).
Bamber, R.N. 1985. Coarse substrate benthos of Kingsnorth outfall lagoon, with observations on Petricola pholadiformis Lamarck. Central Electricity Research Laboratories Report TPRD/L 2759/N84.
Duval, D.M. 1963. The biology of Petricola pholadiformis Lamarck (Lamellibranchiata: Petricolidae). Proceedings of the Malacological Society. 35: 89-100.
Hayward, P.J., & Ryland, J.S. eds. 1990. The marine fauna of the British Isles and north-west Europe. 2 vols. Oxford, Clarendon Press.
International Council for the Exploration of the Sea. 1972. Report of the working group on the introduction of non-indigenous marine organisms. International Council for the Exploration of the Sea.
Naylor, E. 1957. Immigrant marine animals in Great Britain. New Scientist, 2: 21-53.
Rosenthal, H. 1980. Implications of transplantations to aquaculture and ecosystems. Marine Fisheries Review, 42: 1-14.
Tebble, N. 1976. British bivalve seashells. A handbook for identification. 2nd ed. Edinburgh, HMSO, for Royal Scottish Museum.