''Arca zebra'', or the turkey wing ark clam (or simply turkey wing), is a
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 ...
Arcidae, the ark clams.
Description
Distribution
This species is found along the Atlantic coast of North America, ranging from
North Carolina
North Carolina () is a state in the Southeastern region of the United States. The state is the 28th largest and 9th-most populous of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, Georgia and So ...
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 ...
and
Bermuda
)
, anthem = "God Save the King"
, song_type = National song
, song = " Hail to Bermuda"
, image_map =
, map_caption =
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, mapsize2 =
, map_caption2 =
, subdivision_type = Sovereign state
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. It attaches itself to rocks or other hard substrates in shallow water with
byssus
A byssus () is a bundle of filaments secreted by many species of bivalve mollusc that function to attach the mollusc to a solid surface. Species from several families of clams have a byssus, including pen shells (Pinnidae), true mussels (Mytilid ...
threads.
Morphology
The shell of ''Arca zebra'' is boldly striped in brown and white which gives it a resemblance to the wing of a
wild turkey
The wild turkey (''Meleagris gallopavo'') is an Upland game bird, upland ground bird native to North America, one of two extant species of Turkey (bird), turkey and the heaviest member of the order Galliformes. It is the ancestor to the domestic ...
. The whole shell (when both valves are together) has also been likened to Noah's Ark. It is a sturdy shell growing up to 4 in (10 cm) long and 2 in wide. The umbones are separated by a shallow depression, and the hinge is long and straight with about 50 small teeth. There is coarse sculpturing fanning out from the umbones. The inside of the shell is whitish or pale mauve.
File:Arca zebra 01.jpg, Right valve
File:Arca zebra 02.jpg, Left valve
Ecology
Feeding
''Arca zebra'' is a
filter feeder
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feedin ...
, taking in surrounding water and particulates through its reduced
siphons and expelling water while consuming microscopic
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
,
diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...
s, and
phytoplankton
Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
.
Reproduction
''Arca zebra'' is a
protandric hermaphrodite
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.
Many taxonomic groups of animals (mostly invertebrates) do not have sepa ...
, a type of
sequential hermaphrodite
Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes its sex at some point in its life. In particular, ...
with individuals starting out as males and developing female reproductive capacity later in the life cycle.
Reproduction is dependent on food availability and seasonal changes. The gonad tissues of ''Arca zebra'' change in mass throughout the year. The percentage of somatic tissue mass composed of gonad tissue mass sees a large increase from roughly 4% to 40% from May through late September and a large decrease from roughly 40% to 3% from October through January. The percentage then increases slightly from about 3% to 12% in February before decreasing to around 4% between March and April. Highest reproductive activity occurs around July through late September, when the gonad mass is at its greatest.
Gonad development begins when the shells of ''Arca zebra'' are at 18-20mm, and full sexual maturity is reached when the shells are 50-55mm. Larger individuals have greater reproductive output.
''Arca zebra'' has two reproductive periods, one from June to July and the other in September. During each
spawn
Spawn or spawning may refer to:
* Spawn (biology), the eggs and sperm of aquatic animals
Arts, entertainment, and media
* Spawn (character), a fictional character in the comic series of the same name and in the associated franchise
** '' Spawn: ...
, females can spawn up to four million
egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s.
Trochophore
A trochophore (; also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia.
By moving their cilia rapidly, they make a water eddy, to control their movement, and to bring their food closer, to captur ...
larva
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
e, a type of
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 larvae, begin to develop twelve hours after the eggs are
fertilized
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...
. Six days after fertilization, the larvae begin to take on their adult shape.
Eyespots develop seven days after fertilization, with the
foot
The foot ( : feet) is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made ...
developing soon after. Around the same time the foot develops, food-seeking behavior in the
substratum
In linguistics, a stratum (Latin for "layer") or strate is a language that influences or is influenced by another through contact. A substratum or substrate is a language that has lower power or prestige than another, while a superstratum or sup ...
, the sediment at the bottom of the ocean floor, can be observed. Twelve days after fertilization, the larvae begin to settle; about 45% of the larvae reach this stage. Once the larvae reach adulthood, growth mainly happens in the summer, with growth in the summer happening about three times as quickly as in the winter.
Biochemistry
Like other marine bivalves, the biochemical composition in the
tissues of ''Arca zebra'' fluctuate in response to environmental conditions including water temperature, nutrient availability, and contaminant concentration. The
soft tissue
Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ligam ...
s see changes in
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
,
carbohydrate
In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
, and
lipid
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
concentrations.
Anthropogenic inputs into habitats of ''A. zebra'' can cause further fluctuations in the biochemical composition in the tissues. Lipophilic organic contaminants can accumulate in the tissues, and too high a concentration of these contaminants can interfere with normal lipid metabolism, impacting
cell membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...
synthesis and integrity as well as
lysosomal
A lysosome () is a membrane-bound organelle found in many animal Cell (biology), cells. They are spherical Vesicle (biology and chemistry), vesicles that contain Hydrolysis, hydrolytic enzymes that can break down many kinds of biomolecules. A ly ...
activity.
Contaminant inputs can also influence the levels of
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
,
polychlorinated biphenyl
Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1979 and internationally by t ...
,
petroleum hydrocarbons, and
tributyltin
Tributyltin (TBT) is an umbrella term for a class of organotin compounds which contain the (C4H9)3 Sn group, with a prominent example being tributyltin oxide. For 40 years TBT was used as a biocide in anti-fouling paint, commonly known as botto ...
(TBT) in the tissues. TBT is utilized in some boat paints, contributing to its input into the marine habitats of ''A. zebra''. Overexposure to TBT has deleterious impacts on ''A. zebra'', including reduced feeding and increased energy expenditure.
Ecological Effects
''Arca zebra'' is the dominant species in its most well-observed habitats of Chacopata, Venezuela. It lives among a number of other species, most notably the
Akoya pearl oyster, the
leafy jewel box clam, the
eared ark clam, and ''Modiolus squamosus''. It is preyed upon by the
apple murex, the
West Indian murex, and the
bent-beak murex, all species of predatory
murex snails.
''Arca zebra'' also lives in association with a variety of microgastropod species,
gastropods
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. Ther ...
that measure less than 5mm in length. The most common ones found among ''A. zebra'' are some species of the
top-snails,
true whelks, and
margin shells. However, their ecological relationship to ''A. zebra'' is not well understood as their small size makes these species difficult to study.
''Arca zebra'' has a large impact in the ecology of its habitat as beds of ''A. zebra serve'' as both food and shelter for a variety of other shallow water marine organisms.
Regions with greater ''Arca zebra'' bed density also see greater abundance, richness, and
taxonomic distinctness in
decapod crustaceans. The crevices that ''Arca zebra'' beds provide also support the development of richer faunal communities.
Aquaria
''Arca zebra'' are sometimes hitchhikers on
live rock
Live rock is rock from the ocean that has been introduced into a saltwater aquarium. Along with live sand, it confers to the closed marine system multiple benefits desired by the saltwater aquarium hobbyist. The name sometimes leads to misunders ...
, ending up in saltwater fish tanks. They blow out debris in little plumes that may be noticed by the tank owner, leading to their discovery.
Human relevance
Fishing
''Arca zebra'' are caught for human consumption and canning. As efficient filter feeders, they convert large amounts of planktonic mass into biomass usable by humans.
A large bed spanning 70–80 km
2 in the Cacopata region of the
Araya Peninsula, Venezuela has been a site of fishing since 1940. The annual catch generally ranges from 15,792 to 33,986 tons per year but has reached 40,000 tons in the past.
It is a significant income source for Venezuelan
artisanal fisheries. These fisheries employ non-selective fishing methods, resulting in significant
bycatch
Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...
of other
molluscs
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 taxon, extant species of molluscs are recognized. The number of fossil sp ...
, including the endangered
music volute.
Bycatch also frequently includes the aforementioned Akoya pearl oyster, leafy jewel box clam, and apple murex as well as non-mollusc species.
References
{{Taxonbar, from=Q3016072
Arcidae
Bivalves described in 1833