''Codakia orbicularis'' , or the tiger lucine, is a species of

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Lucinidae Lucinidae, common name hatchet shells, is a family of saltwater clams, marine bivalve molluscs. These bivalves are remarkable for their endosymbiosis with sulphide-oxidizing bacteria. Characteristics The members of this family have a worldwide ...

. It can be found along the Atlantic coast of North America, ranging from

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

to the

West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater A ...

Description

''Codakia orbicularis'' grows to maximum length of about . The shell valves are nearly circular, the outer surface being sculptured with fine concentric rings and closely-packed radial lines. The lunule, a depressed area near the hinge, is heart-shaped, with the right valve lunule being larger than the left. The

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods and ...

, a thin outside layer, is brown and the valves are mainly white; there is often a pinkish tinge near the interior margin. The shell is more laterally compressed than the smaller dwarf tiger lucine (''

Ctena orbiculata ''Ctena orbiculata'', commonly known as the dwarf tiger lucine, is a species of bivalve mollusc in the family Lucinidae. It can be found along the Atlantic coast of North America, ranging from North Carolina to the West Indies. Description ''Cte ...

''). Like other members of its family

, ''Codakia orbicularis'' does not have an inhalant siphon, instead rolling its elongated foot into a mucus-lined tube and drawing water into the gill cavity through this. It does have an exhalant siphon which is formed from a highly extensible mantle flap and can be inverted and drawn back into the shell. The gill cavity contains chemosymbiotic sulphur-oxidizing bacteria housed in

bacteriocyte A bacteriocyte (Greek for ''bacteria cell''), also known as a mycetocyte, is a specialized adipocyte found primarily in certain insect groups such as aphids, tsetse flies, German cockroaches, weevils. These cells contain endosymbiotic organisms su ...

s which contribute to the clam's nutritional requirements.

Distribution and habitat

''Codakia orbicularis'' is native to the western Atlantic Ocean where its range includes from

and the northern coast of the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

. It lives immersed in soft sediment on the seabed, typically in ''

Thalassia testudinum ''Thalassia testudinum'', commonly known as turtlegrass, is a species of marine seagrass. It forms meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico. Turtle grass and other seagrasses form meadows A meado ...

'' seagrass beds. Its maximum depth is . The bacterial symbionts enable these burrowing bivalves to colonise sulfide-rich sediments with low oxygen levels that are unsuited to many other bivalves.

Ecology

''Codakia orbicularis'' is a large edible shellfish and its life cycle has been studied to see whether it is suitable for

mariculture Mariculture or marine farming is a specialized branch of aquaculture (which includes freshwater aquaculture) involving the cultivation of marine organisms for food and other animal products, in enclosed sections of the open ocean ( offshore mari ...

. In the Bahamas, spawning takes place between May and October. The large-yolked eggs are enclosed in a thick gelatinous membrane and the early developmental stages take place inside this capsule. The later stages of the

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod ...

larva are

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic and

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

occurs about 16 days after fertilisation. During their growth and development, the larvae may obtain nutrition from the

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

chemosynthetic bacteria present in their tissues.

References

{{Taxonbar, from=Q3012702 Lucinidae Molluscs of the Atlantic Ocean Molluscs described in 1758 Taxa named by Carl Linnaeus