Petricolaria pholadiformis (false angel wing)
- Summary of Invasiveness
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Water Tolerances
- Means of Movement and Dispersal
- Pathway Causes
- Pathway Vectors
- Impact Summary
- Environmental Impact
- Threatened Species
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Gaps in Knowledge/Research Needs
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Petricolaria pholadiformis (Lamarck, 1818)
Preferred Common Name
- false angel wing
Other Scientific Names
- Gastanella tumida Verril, 1872
- Petricola lata Dall, 1925
- Petricola pholadiformis Lamarck, 1818
International Common Names
- English: American piddock
- Spanish: falso ala de ange
- French: fausse aile d' ange; petricole d' Amérique; petricole pholadiforme
Local Common Names
- Denmark: Amerikansk boremusling
- Germany: Amerikanische bohrmuschel; Engelsflügel
- Netherlands: Amerikaanse boormossel
- Norway: Amerikansk boreskjell
- Sweden: Amerikansk bormussla
Summary of InvasivenessTop of page
P. pholadiformis is a boring bivalve that lives in the shallow waters of coastal areas. Outside its native range, it has established viable populations in most areas that have been invaded. Its introduction has been attributed to its accidental presence in oyster shipments coming to Europe from the USA for aquaculture purposes, but also to shipping and natural dispersal. It appears that reduced salinity facilitates its establishment (Zenetos et al., 2009). Although P. pholadiformis is present in the North Sea for more than a hundred years, its expansion and distribution are relatively limited. It was first reported as an invasive species in the Netherlands and Belgium where it outcompeted a native boring bivalve species Barnea candida, although no such effect has been documented in other countries (Budd, 2005).
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Mollusca
- Class: Bivalvia
- Subclass: Heterodonta
- Order: Veneroida
- Unknown: Veneroidea
- Family: Petricolidae
- Genus: Petricola
- Species: Petricolaria pholadiformis
Notes on Taxonomy and NomenclatureTop of page
Petricola pholadiformis belongs to the genus Petricola Lamarck, 1801, of the family Petricolidae Deshayes, 1831, which belongs to the superfamily Veneroidea Rafinesque, 1815. There are five genera in the family Petricolidae: Choristodon, Cooperella, Mysia, Petricola, and Rupellaria. Members of the genus Petricola include Petricolacaliforniensis Pilsbry and Lowe, 1932; Petricola carditoides (Conrad, 1837); Petricola hertzana Coan, 1997; Petricola lapicida (Gmelin, 1791); Petricola lithophaga (Retzius, 1786); Petricola lucasana Herlein and Strong, 1948.
However, for the purposes of this datasheet the name Petricolaria pholadiformis with be used, with Petricola pholadiformis placed as a synonym, as in agreement with the World Register of Marine Species (http://www.marinespecies.org/).
DescriptionTop of page
Adult P. pholadiformis have a thin fragile shell with an elongate oval outline and cylindrical shape, which is similar in sculpture on both sides. The anterior end is short and rounded, and the posterior is elongated and slightly gaping. There is a well defined lunule in the front, whereas the beaks (tips) of each valve are in the anterior half, and turn downward and inwards. Both valves have clearly visible teeth.
The outside surface of the shell is covered with strong ribs (>40) radiating from the top, that cross numerous and distinct concentric growth lines. Ribs at the anterior end are large, coarse, widely spaced and elevated. These squamous projections are used by the animal to ‘bore’ through the substrate. Ribs at the posterior end are crowded and faint. The inside of the shell is smooth and white in colour. The ligament is external and prominent, stretching a quarter of the way between the beaks to the posterior margin.
The colour of the shell ranges from off-white to dirty cream yellow. Lime white, fawn and yellowish white are the most usual shell colourations, and the periostracum is dark brown. Older specimens are coloured brownish yellow.
The length of the shell ranges from 25-80 mm, but specimens are commonly up to 65 mm long.
Larvae of this species have a total length of 60-185 µm. The straight-hinge stage ends at ~105 µm length, at which time a broadly rounded umbo develops. The anterior end is slightly longer than posterior, the ends of the shell are nearly equally rounded, and the shoulders are straight and slope steeply. There is no distinctive color, though the margin is dark. The eye spot is not pigmented and the shell is heavier than in most clams. Metamorphosis occurs at ~175 µm (Chanley and Andrews, 1971). To summarize, the key identification features of this species are:
- Shell is thin, brittle, equivalve, inequilateral, elongate and oval in outline.
- Beaks in anterior half are turned downwards and inwards, sometimes set back from the dorsal edge.
- Colour of the shell is off-white or fawn, with a dark brown periostracum.
- Interior of the shell white, with the coarse anterior ribs showing through.
- Prominent ligament.
- Sculpturing of concentric rings is crossed anteriorly by about 40 ribs that are spined at the anterior end.
- Anterior margin of shell crenulates where the large ribs meet it, while it is smooth elsewhere (Budd, 2005).
To summarize, the key identification features of this species are:
DistributionTop of page
The false angel wing P. pholadiformis originates from the western Atlantic, where it is present from the Gulf of St Lawrence to Uruguay (Abbott, 1974). In Great Britain, it is present along the south and west English coasts (Davison, 1996), from Lyme Regis, in Dorset, to the Humber. It is most common off the coast of Essex (River Crouch) (JNCC, 2009) and the Thames Estuary (River Medway). There are also isolated records from north Wales and Cornwall (Budd, 2005). It is not present in Scotland (Davison, 1996).
In the Netherlands it is present along the entire coastline, is locally very abundant, and is one of the most common species of the Dutch coast (Wolff, 2005). In Denmark, P. pholadiformis was first reported in 1905 from the Wadden Sea, and is presently established in the Wadden Sea, along the Skagerrak coast, the Limfjord, and in the northern Kattegat (Jensen and Knudsen, 2005).
The first record of P. pholadiformis from the Mediterranean Sea was in the Saronikos Gulf (southern Aegean Sea), Greece (Zenetos et al., 2009).
A record of this species from the western Mediterranean (Spain and Tunisia) (Poutiers, 1987), was not substantiated by literature, and was therefore disputed (Zenetos et al., 2004). According to local experts, the species is absent from both areas. However, the species was recently detected in the Nervión estuary, Spain, (southeastern Bay of Biscay) (Zorita et al., 2013), It is also reported as established in France (North Sea) (Müller, 2004; Dewarumez, 2011).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Atlantic, Northeast||Widespread||Introduced||<1890||Invasive||Naylor, 1957|
|Atlantic, Northwest||Present||Native||Not invasive||Harvey-Clark, 1997|
|Atlantic, Western Central||Present||Native||Not invasive||Hill et al., 2005|
|Mediterranean and Black Sea||Present, few occurrences||Introduced||1985||Zenetos et al., 2004||Saronikos Gulf|
|Pacific, Eastern Central||Present||Introduced||1927||Ray, 2005||Newport Bay, San Francisco Bay, Willapa Bay|
|Tunisia||Absent, unreliable record||Introduced||Poutiers, 1987|
|Canada||Present||Native||Not invasive||Harvey-Clark, 1997|
|Mexico||Present||Native||Not invasive||Hill et al., 2005|
|USA||Present||Native||Not invasive||Hill et al., 2005|
|-Washington||Present||Introduced||1943||Cohen et al., 2001|
|Belgium||Present||Introduced||1899||Invasive||Loppens, 1905||unintentionally released|
|France||Localised||Introduced||1992||Dewarumez et al., 2011|
|Germany||Present||Introduced||1896||Schlesch, 1932||In the Baltic Sea since 1927: unintentional-release from oyster farms (Schlesch 1932). In the North Sea|
|Greece||Present, few occurrences||Introduced||1985||Zenetos et al., 2009|
|Spain||Present||Introduced||2007||Zorita et al., 2013|
History of Introduction and SpreadTop of page
P. pholadiformis was introduced accidentally into the United Kingdom, in shipments of the American oyster Crassostrea virginica, sometime before 1890 (Eno et al., 1997). It was subsequently reported from Germany (1896) (NOBANIS, 2009) and the Wadden Sea, Denmark (1905) (Jensen and Knudsen, 2005). The species became common in Kattegat from where it spread to the coasts of Belgium (1899) and the Netherlands (1905) (ICES, 1972; Wolff, 2005). It is unknown how it spread from the British Isles to the shores of continental Europe, although expansion of the larval stage with marine currents is the most likely reason. Rosenthal (1980) suggested that P. pholadiformis may also have spread via driftwood. It was later reported from Norway (1955), and Sweden (NOBANIS, 2009).
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Belgium||1899||Breeding and propagation (pathway cause)||Yes||Loppens (1905)||Unintentional|
|California||1927||Aquaculture (pathway cause)||Yes||Ray (2005)||Unintentional|
|Denmark||1905||Breeding and propagation (pathway cause)||Yes||Bagge (1968)||Unintentional|
|Germany||1896||Breeding and propagation (pathway cause)||Yes||Schlesch (1932)||Unintentional|
|Greece||1985||Yes||Zenetos et al. (2009)||Unintentional, from the Atlantic|
|Netherlands||1905||Breeding and propagation (pathway cause)||Yes||Denker (1907)||Unintentional|
|Norway||1955||Breeding and propagation (pathway cause)||Yes||Rustad (1955)||Unintentional|
|Sweden||1905||Breeding and propagation (pathway cause)||Hessland (1944)||Unintentional|
|UK||USA||<1890||Aquaculture (pathway cause)||Yes||Naylor (1957)||Unintentional|
Risk of IntroductionTop of page
HabitatTop of page
As the animal becomes older, it bores deeper into the substratum. According to the literature, the species in its native range inhabits environments with salinities between 29 and 35 ppt, while in the Baltic Sea it is reported from salinities 10-30 ppt (Gollasch and Mecke, 1996). According to Castagna and Chanley (1973), the lower salinity tolerance of P. pholadiformis is 7.5-10 ppt.
Habitat ListTop of page
|Coastal areas||Principal habitat|
|Inshore marine||Principal habitat|
|Benthic zone||Principal habitat|
Biology and EcologyTop of page
Please see Espiñeira et al. (2009) for more on the genetics of this species.
ClimateTop of page
|Cf - Warm temperate climate, wet all year||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year|
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Cw - Warm temperate climate with dry winter||Preferred||Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)|
Water TolerancesTop of page
|Parameter||Minimum Value||Maximum Value||Typical Value||Status||Life Stage||Notes|
|Salinity (part per thousand)||29||35||Optimum||7.5-35 tolerated (Castagna and Chanley, 1973)|
Means of Movement and DispersalTop of page
There is no record of this species being intentionally introduced in any area.
Pathway CausesTop of page
Pathway VectorsTop of page
Impact SummaryTop of page
Environmental ImpactTop of page
P. pholadiformis bores into clay, peat, mud, sand and other soft sediments, and may therefore modify habitats (Cohen and Carlton, 1995).This burrowing creates a generally uneven surface on a small scale (5-15 cm) providing habitats for other animals that inhabit vacant burrows and crevices in the clay (Marshall, 2008).
Threatened SpeciesTop of page
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Abundant in its native range
- Highly adaptable to different environments
- Long lived
- Ecosystem change/ habitat alteration
- Modification of natural benthic communities
- Reduced native biodiversity
- Threat to/ loss of native species
- Highly likely to be transported internationally accidentally
Similarities to Other Species/ConditionsTop of page
P. pholadiformis may be confused with white piddock (Barnea candida), a native species in several countries, including Denmark, Sweden, Germany, the Netherlands and Britain. P. pholadiformis bears a superficial resemblance to Barnea candida, but has 2 cardinal teeth in the right valve and 3 in the left valve where Barnea candida has none (Tebble, 1966; Budd, 2005). P. pholadiformis may also be confused with the oval piddock (Zirphaea crispata), which can be distinguished by a conspicuous groove in each valve of its shell and a large gape where its foot protrudes.
Gaps in Knowledge/Research NeedsTop of page
Unfortunately, there is very little actual data on most aspects of the biology and ecology of the false angel wing P. pholadiformis.
ReferencesTop of page
Budd GC, 2005. Petricola pholadiformis. American piddock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. http://www.marlin.ac.uk/species/Petricolapholadiformis.htm
Cohen AN, 1998. Ships' Ballast Water and the Introduction of Exotic Organisms into the San Francisco Estuary: Current Status of the Problem and Options for Management. Richmond CA, : San Francisco Estuary Institute.
Cohen AN; Berry HD; Mills CE; Milne D; Britton-Simmons K; Wonham MJ; Secord DL; Barkas JA; Bingham B; Bookheim BE; Byers JE; Chapman JW; Cordell JR; Dumbauld B; Fukuyama A; Harris LH; Kohn AJ; Li K; Mumford TF; Radashevsky V; Sewell AT; Welch K, 2001. A rapid survey of exotic species in the shallow waters of Elliott Bay, Totten and Eld Inlets, and Willapa Bay. WSEE 2000. Report prepared for the Nearshore Habitat Program, Washington State Department of Natural Resources., 1-52 pp.
Cohen AN; Carlton JT, 1995. Biological Study. Nonindigenous Aquatic Species in a United States Estuary: A Case Study of the Biological Invasions of the San Francisco Bay and Delta. A Report for the United States Fish and Wildlife Service, Washington DC, and The National Sea Grant College Program, Connecticut Sea Grant, NTIS Report Number PB96-166525., 701. http://elib.cs.berkeley.edu/TR/ELIB:701
Dewarumez JM; Gevaert F; Massé C; Foveau A; Desroy N; Grulois D, 2011. [English title not available]. Les espèces marines animales et végétales introduites dans le bassin Artois-Picardie. UMR CNRS 8187 LOG et Agence de l'Eau Artois-Picardie, 140 pp.
Espiñeira M; González-Lavín N; Vieites JM; Santaclara FJ, 2009. Development of a method for the genetic identification of commercial bivalve species based on mitochondrial 18S rRNA sequences. Journal of Agricultural and Food Chemistry, 57(2):495-502. http://pubs.acs.org/journals/jafcau/index.html
Gollasch S; Mecke R, 1996. [English title not available]. (Eingeschleppte Organismen) In: Warnsignale aus der Ostsee [ed. by Lozan JL, Lampe R, Matthaus W, Rachor E, Rumohr H, Westernhagen H] Berlin, : Parey Buchverlag, pp. 146-150.
Hessland I, 1944. [English title not available]. (Petricola pholadiformis - en nordamerikansk mussla under frammarsch pa Sveriges västkust.) Fauna och Flora, 39(1):15-26.
Hill M; Baker R; Broad G; Chandler PJ; Coop GH; Ellis J; Jones D; Hoyland C; Laing I; Longshaw M; Moore N; Parrott D; Pearman D; Preston C; Smith RM; Waters R, 2005. Audit of Non-native species in England. English Nature Research Reports, No 662:82 pp.
Marshall CE, 2008. Mytilus edulis and piddocks on eulittoral firm clay. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth, : Marine Biological Association of the United Kingdom. http://www.marlin.ac.uk/habitatecology.php?habitatid=95&code=2004
Poutiers JM, 1987. Bivalves. In: Fiches FAO d'identification des espèces pour les besoins de la pêche. - Méditerranée et Mer Noire. Zone de pêche 37. Révision 1 [ed. by Fischer W, Schneider M, Bauchot M-L]: CEE, FAO, 369-512.
Ray GL, 2005. Invasive estuarine and marine animals of California. Technical Notes Collection (ERDC/TN ANSRP-05-2). Vicksburg, MS, : U.S. Army Engineer Research and Development Center. http://el.erdc.usace.army.mil/ansrp
Zenetos A; Ovalis P; Vardala-Theodorou E, 2009. The American piddock Petricola pholadiformis Lamarck, 1818 spreading in the Mediterranean Sea. Aquatic Invasions, 4(2):385-387. http://www.aquaticinvasions.ru/2009/AI_2009_4_2_Zenetos_etal.pdf
Zorita I; Solaun O; Borja A; Franco J; Muxika I; Pascual M, 2013. Spatial distribution and temporal trends of soft-bottom marine benthic alien species collected during the period 1989-2008 in the Nervión estuary (southeastern Bay of Biscay). Journal of Sea Research [XVII Iberian Symposium of Marine Biology Studies, Donostia-San Sebastian, Spain, 11-14 September.], 83:104-110. http://www.sciencedirect.com/science/article/pii/S1385110113000804
ContributorsTop of page
15/02/16 Updated by:
Argyro Zenetos, Institute of Marine Biological Resources and Inland Waters, Hellenic Centre for Marine Research, P.O. BOX 712, Anavissos 19013, Greece
21/07/09 Original text by:
Argyro Zenetos, Institute of Oceanography, Hellenic Centre for Marine Research, P.O. BOX 712, Anavissos 19013, Greece
Distribution MapsTop of page
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