Common cockle

The common cockle (Cerastoderma edule) is a species of edible saltwater clam, a marine bivalve mollusc in the family Cardiidae, the cockles. It is found in waters off Europe, from Iceland in the north, south into waters off western Africa as far south as Senegal. The ribbed oval shells can reach 6 centimetres (2.4 in) across and are white, yellowish or brown in colour. The common cockle is harvested commercially and eaten in much of its range.

Common cockle
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Bivalvia
Subclass: Heterodonta
Order: Cardiida
Family: Cardiidae
Genus: Cerastoderma
Species:
C. edule
Binomial name
Cerastoderma edule
Synonyms
  • Cardium belgicum De Malzine, 1867
  • Cardium crenulatum Lamarck, 1819
  • Cardium edule Linnaeus, 1758 (basionym)
  • Cardium edule burchanae Girscher, 1938
  • Cardium edule var. batesoni Bucquoy, Dautzenberg & Dollfus, 1892
  • Cardium edule var. loppensi Mars, 1951
  • Cardium edule var. major Bucquoy, Dautzenberg & Dollfus, 1892
  • Cardium mercatorium Coen, 1915
  • Cardium nunninkae Lucas, 1984
  • Cardium obtritum Locard, 1886
  • Cardium quadrarium Reeve, 1845
  • Cardium vulgare Da Costa, 1778
  • Cerastoderma edule var. sinicola Lacourt, 1974
  • Cerastoderma nunninkae Lucas, 1984

Taxonomy and naming

The common cockle was one of the many invertebrate species originally described by Carl Linnaeus in the landmark 1758 10th edition of Systema Naturae, where it was given its old binomial name Cardium edule.[2] The species name is derived from the Latin adjective ĕdūlis "edible".[3] Italian naturalist Giuseppe Saverio Poli erected the genus Cerastoderma in 1795, making the common cockle the type species as Cerastoderma edule.[4] The genus name is derived from the Ancient Greek words keras "horn" and derma "skin".[5] For many years it was referred to by both names.[4]

Other common names in English are edible cockle and common edible cockle.[1] On account of its heart-like shape and its similarity to mussels, it is called the heart mussel in German and Scandinavian languages.[6]

Description
Cerastoderma edule a) foot b) exhalant siphon c) branchial or inhalant siphon d) edge of mantle e) ligament f) umbones or beaks of the shell

It typically reaches from 3.5 centimetres (1.4 in) to 5 centimetres (2.0 in) in length,[7] but sometimes it reaches 6 centimetres (2.4 in).[6] The shells are pale or whitish yellow, grubby white, or brown.[6][7] The shell is oval, and covered by ribs, which are flattened in the middle part of the shell. The digestive glands are light brown to dark green.[4]

In contrast, the similar lagoon cockle has an elongated shell posteriorly, black digestive glands and is found in substrate of stagnant water.[4]

Distribution and habitat

This species is found in coastal areas of the northern and eastern Atlantic Ocean. It is widely distributed from Iceland and Norway in Europe, to Senegal along the coast of west Africa.[6][7] The common cockle is one of the most abundant species of molluscs in tidal flats located in the bays and estuaries of Europe. It plays a major role as a source of food for crustaceans, fish, and wading birds.

Ecology

This species is a filter feeder, meaning that it feeds by straining water to obtain suspended matter and food particles.[8] Water is inhaled through an inhalant siphon, and exhaled through an exhalant siphon.[7]

It tolerates a wide range of salinity (euryhaline), and wide range of temperatures (eurythermic), which helps to explain its very extensive range. It has a first spawning period in early summer, and a second one in the fall. Lifespan is typically five to six years, though it may perish earlier due to predation by humans as well as crabs, flounder, and various birds especially including oystercatchers.[8] A green shore crab (Carcinus maenas) can consume up to 40 common cockles a day, eating smaller cockles (under 1.5 cm diameter) much more quickly than larger ones. Hence they could have a greater impact in lean seasons where cockles did not grow so quickly.[9]

Parasites and diseases

The cercozoan species Marteilia cochillia is a parasite of the common cockle, having caused a collapse in commercial harvests of cockle beds in Galicia in 2012. [10] A survey of cockle beds in Galicia found that infestation by the gregarine parasite Nematopsis was widespread, and that the most common pathological finding was disseminated neoplasia.[11]

Uses
Cockle shell ridges imprinted in fragment of Neolithic Cardial ware

These animals were probably a significant food source in hunter-gatherer societies of prehistoric Europe, and the clay remains of shell-imprints have been found. The clay is imprinted with fine decorations, repetitions of the distinct curved ridges, undulating lines and/or edges characteristic to the cockle shell, a natural resource of coastal waters.

Cardial ware is the name of the Neolithic pottery from maritime cultures that colonized Mediterranean shores c. 6000 – 5,500 BC, this name being based upon the old binomial name of the species: Cardium edule.

In the 1800s, a song called "Molly Malone" was first published (also known as "Cockles and Mussels"), later becoming the unofficial song of Dublin, Ireland. The lyrics describe Molly Malone selling the common cockle in the streets of that city.[6]

As food
Cockle bed with cockles (Cerastoderma edule) near De Cocksdorp on the island of Texel in the Dutch province of North Holland

This cockle is cooked and eaten in several countries (including the United Kingdom, France, Germany, Ireland, Japan, Portugal and Spain). It is also sometimes eaten pickled, or raw.[6]

An important species for the fishing industry, it is commercially fished in the United Kingdom, Ireland and France by suction dredge (like a huge vacuum cleaner) and also raking by hand. Previously the greatest catch was from the Netherlands, but now fisheries restrictions have been put in place due to environmental concerns. Similar measures have been established elsewhere, for example in Scotland where dredging with vehicles is prohibited, and in parts of England and Wales where only old-fashioned hand-gathering is permitted (using a long plank that is rocked back and forth on the sand).[12]

This species is also used in aquaculture. Farming of cockles is ongoing in the UK, the Netherlands and Portugal. However, production in those countries has not been very stable; for example, production fell from 107,800 tons in 1987 to 40,900 tons in 1997.[13]

Gathering this species can be dangerous. In 2004, the incoming tide at Morecambe Bay in England caused 23 cockle-gatherers to die.[5] In addition to being a food source, their shells have also been used industrially as a source of lime.[5]

References
  1. Jan Johan ter Poorten & Serge Gofas (2011). "Cerastoderma edule (Linnaeus, 1758)". World Register of Marine Species. Retrieved April 20, 2011.
  2. Linnaeus, Carl (1758). Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis (in Latin). Vol. I (10th revised ed.). Holmiae: (Laurentii Salvii). p. 681 – via The Internet Archive.
  3. Simpson, D.P. (1979). Cassell's Latin Dictionary (5th ed.). London: Cassell Ltd. p. 207. ISBN 0-304-52257-0.
  4. Boyden, C. R. (1971). "A note on the nomenclature of two European cockles". Zoological Journal of the Linnean Society. 50 (3): 307–10. doi:10.1111/j.1096-3642.1971.tb00765.x.
  5. Chambers, Paul. British Seashells: A Guide for Collectors and Beachcombers, p. 158 (Casemate Publishers, 2009).
  6. Davidson, Alan. The Oxford Companion to Food, p. 201 (Oxford University Press, 2014).
  7. Considine, Douglas and Considine, Glenn. Van Nostrand's Scientific Encyclopedia, p. 2086 (Springer Science & Business Media, 2013).
  8. Dauvin, Jean-Claude. Biological heritage and food chains, p. 25 (Quae, Centre de coopération internationale en recherche agronomique pour le développement, 2006).
  9. Sanchez-Salazar, M.E.; Griffiths, C.L.; Seed, R. (1987). "The effect of size and temperature on the predation of cockles Cerastoderma edule (L.) by the shore crab Carcinus maenas (L.)". Journal of Experimental Marine Biology and Ecology. 111 (2): 181–93. doi:10.1016/0022-0981(87)90054-2.
  10. Villalba, Antonio; Iglesias, David; Ramilo, Andrea; Darriba, Susana; Parada, Jose M.; No Couto, Edgar; Abollo, Elvira; Molares, Jose; Carballal, MJ (2014). "Cockle Cerastoderma edule fishery collapse in the Ría de Arousa (Galicia, NW Spain) associated with the protistan parasite Marteilia cochillia". Diseases of Aquatic Organisms. 109 (1): 55–80. doi:10.3354/dao02723. PMID 24781796.
  11. Carballal, Marıa Jesus; Iglesias, David; Santamarina, Jesús; Ferro-Soto, Beatriz; Villalba, Antonio (2001). "Parasites and Pathologic Conditions of the Cockle Cerastoderma edule Populations of the Coast of Galicia (NW Spain)" (PDF). Journal of Invertebrate Pathology. 78 (2): 87–97. doi:10.1006/jipa.2001.5049. PMID 11812111. Archived from the original (PDF) on 2017-12-01. Retrieved 2017-11-26.
  12. Aikens, Tom. Fish, p. 547 (Random House, 2012).
  13. Spencer, Brian. Molluscan Shellfish Farming, p. 103 (John Wiley & Sons, 2008).
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