Ark clam
Encyclopedia
Ark clam is the common name
for a family of small to large-sized saltwater clams or marine
bivalve molluscs in the family
Arcidae. Ark clams vary both in shape and size. They number about 200 species worldwide.
The shells of ark clams are often white or cream, but in certain species, the shell is striped with, tinted with, or completely colored with a rich brown. In life the shell of most species has a thick layer of brown periostracum
covering the harder calcareous part of the shell. In some species such as Barbatia
, this outer horny covering is tufted at the end of the shell into something that resembles a beard, hence the name Barbatia or bearded one.
The group is known as "ark shells" because species such as Arca have a large flat area in front of the boss of the shield, which, in an undamaged shell, can somewhat illustrate a deck
, with the rest of the shell perhaps illustrating an ancient wooden boat such as Noah's ark
is thought to have been.
All ark shells have a long straight hinge line with a single row of numerous small and unspecialized "teeth". This is known as a "taxodont dentition" and represents an ancient ancestor. This kind of hinge line is also found in the bivalve families Glycymerididae
, Nuculidae
and Nuculanidae
.
The thick outer skin or periostracum
of an ark clam can act as camouflage
, such that the shells can sometimes look like stones when lying on the bottom.
Large ark clams, such as Arca zebra
, are commonly used as bait, as well as food, throughout the Caribbean
.
Genera within the family Arcidae include:
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
for a family of small to large-sized saltwater clams or marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
bivalve molluscs in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Arcidae. Ark clams vary both in shape and size. They number about 200 species worldwide.
The shells of ark clams are often white or cream, but in certain species, the shell is striped with, tinted with, or completely colored with a rich brown. In life the shell of most species has a thick layer of brown periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
covering the harder calcareous part of the shell. In some species such as Barbatia
Barbatia
Barbatia is a genus of ark clams, in the family Arcidae.-Species:* Barbatia cancellaria - red-brown ark* Barbatia candida - white-beard ark* Barbatia divaricata...
, this outer horny covering is tufted at the end of the shell into something that resembles a beard, hence the name Barbatia or bearded one.
The group is known as "ark shells" because species such as Arca have a large flat area in front of the boss of the shield, which, in an undamaged shell, can somewhat illustrate a deck
Deck (ship)
A deck is a permanent covering over a compartment or a hull of a ship. On a boat or ship, the primary deck is the horizontal structure which forms the 'roof' for the hull, which both strengthens the hull and serves as the primary working surface...
, with the rest of the shell perhaps illustrating an ancient wooden boat such as Noah's ark
Noah's Ark
Noah's Ark is a vessel appearing in the Book of Genesis and the Quran . These narratives describe the construction of the ark by Noah at God's command to save himself, his family, and the world's animals from the worldwide deluge of the Great Flood.In the narrative of the ark, God sees the...
is thought to have been.
All ark shells have a long straight hinge line with a single row of numerous small and unspecialized "teeth". This is known as a "taxodont dentition" and represents an ancient ancestor. This kind of hinge line is also found in the bivalve families Glycymerididae
Glycymerididae
Glycymerididae, previously known as Glycymeridae, common names dog cockles or bittersweets, is a worldwide family of marine bivalve mollusks, related to the ark clams. In this family the shell is generally round in outline, is slightly longer than it is wide, and the external ligament lacks...
, Nuculidae
Nuculidae
Nuculidae is a family of small saltwater clams in the order Nuculoida. Species in this family are commonly known as nut clams.The nomenclature of the Western European species in this family is still uncertain. Their systematics has been based mainly on their feces. -Genera:* Acila H. Adams and A...
and Nuculanidae
Nuculanidae
Nuculanidae is a family of small bivalve molluscs in the order Nuculanoida.Nuculanidae species are found in all seas, from shallow to deep water.-Taxonomy:* Acutispinula** Acutispinula hilleri...
.
The thick outer skin or periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
of an ark clam can act as camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
, such that the shells can sometimes look like stones when lying on the bottom.
Large ark clams, such as Arca zebra
Arca zebra
Arca zebra, or the turkey wing ark clam, is a bivalve mollusc in the family Arcidae. It can be found along the Atlantic coast of North America, ranging from North Carolina to the West Indies and Bermuda...
, are commonly used as bait, as well as food, throughout the Caribbean
Caribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
.
Genera
- Acar Gray, 1857
- AnadaraAnadaraAnadara is a genus of saltwater bivalves, ark clams, in the family Arcidae.-Species:Species within the genus Anadara include:* Anadara auriculata Lamarck * Anadara baughmani Hertlein, 1951 - baughman ark, skewed ark...
Gray, 1847 - Arca Linnaeus, 1758
- BarbatiaBarbatiaBarbatia is a genus of ark clams, in the family Arcidae.-Species:* Barbatia cancellaria - red-brown ark* Barbatia candida - white-beard ark* Barbatia divaricata...
Gray, 1847 - Bathyarca Kobelt, 1891
- Bentharca Verrill and Bush, 1898
- Samacar Iredale, 1936
- SeniliaSeniliaSenilia is a genus of edible saltwater clams, marine bivalve mollusks in the family Arcidae, the ark shells....
Linnaeus, 1758