Pholadidae

Pholadidae
Temporal range: Jurassic–Recent
One valve of a shell of Cyrtopleura costata
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Order: Myida
Superfamily: Pholadoidea
Family: Pholadidae
Lamarck, 1809
Genera

See text

Pholadidae, known as piddocks or angelwings, are a family of bivalve molluscs similar to a clam.

Background

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Piddocks are unique in that each side of their shells is divided into 2 or 3 separate sections. Furthermore, one of the piddock's shells has a set of ridges or "teeth", which they use to grind away at clay or soft rock and create tubular burrows. The shape of these burrows is due to the rotating motion of the piddock as it grinds the rock to make its home. The piddock stays in the burrow it digs for the entirety of its eight-year lifespan, with only its siphon exposed to take in water that it filters for food. When the piddock dies and leaves an empty tubular burrow, other marine life such as sea anemone, crabs and other molluscs may use the burrow.

Some species of Pholadidae may reach up to 18 cm (7″). Their coloration is typically white, though through consumption of red tide algae some may develop a pink coloration.

  • The Atlantic mud-piddock, Barnea truncata, often referred to as the fallen angelwing, is classed among the angelwing varieties, growing up to 5.7 cm (2¼″) and is similar to other angelwings but with weaker sculpture. One end is squared off and the other end pointed. Loose accessory plates are located above the hinge on live specimens. It possesses a white exterior and interior. It burrows into mud, clay or softwood. Occasionally it is washed onto sounds and ocean beaches, and has a habitat range from Nova Scotia[1] to Brazil. This fragile shell is rarely dug from mud without breaking. It burrows deeply and has long, united siphons.
  • The false angelwing Petricola pholadiformis, is also classed among varieties of angelwing, growing up to 7 cm (2¾″). It has a thin, elongate shell resembling a small angelwing but lacks the rolled-out hinge area. Its beak is at one end of the shell with strong radial ribbing on the beak end. Teeth are located on hinge and a deep pallial sinus and partially united siphons. It has a white exterior and interior. It typically burrows into hard surfaces such as clay or peat in intertidal zones. It is commonly found on sounds and ocean beaches with a range from Canada to Uruguay.
  • The common piddock (Pholas dactylus) is known for its bioluminescence[2][3] and was investigated by Raphaël Dubois in his 1887 discovery of luciferin.

Genera and selected species

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Two views of a whole shell of Barnea candida
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  • Valves of the Atlantic mud-piddock or fallen angelwing, Barnea truncata
    Valves of the Atlantic mud-piddock or fallen angelwing, Barnea truncata
  • Siphons of the rough piddock, Zirfaea pilsbryi in Puget Sound
    Siphons of the rough piddock, Zirfaea pilsbryi in Puget Sound
  • burrows, 2.5 cm (1″) or less, in calcic rock, coast Boulogne - Calais (France)
    burrows, 2.5 cm (1″) or less, in calcic rock, coast Boulogne - Calais (France)
  • Angelwing and associated burrows
    Angelwing and associated burrows

See also

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References

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  1. ^ http://www.registrelep.gc.ca/virtual_sara/files/cosewic/sr_Atlantic%20Mud-piddock_0810_e.pdf [dead link]
  2. ^ Basic information for Pholas dactylus (Common piddock)
  3. ^ Vincent Pieribone and David F. Gruber. Aglow in the Dark: The Revolutionary Science of Biofluorescence. Harvard University Press, 2005.
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