 | This article includes a list of general references, but it lacks sufficient corresponding inline citations .(April 2009) |
| Atrina rigida | |
|---|---|
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Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Bivalvia |
| Order: | Pteriida |
| Family: | Pinnidae |
| Genus: | Atrina |
| Species: | A. rigida |
| Binomial name | |
| Atrina rigida (Lightfoot, 1786) | |
| Synonyms | |
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Atrina rigida, commonly called the rigid pen shell, is a species of bivalve mollusc in the family Pinnidae.
The rigid shell has a pair of thick spiny valves held together by ligaments that run along the entire dorsal side of the bivalve. The bivalve is triangular with 15 to 25 low ribs radiating from the pointed anterior end (or umbo) to the large posterior edge. The exterior of the shell is usually a dull brownish color with many small tube-like spines along the crest of its radiating ribs. Its anterior end is typically buried in fine substrate and attached by byssal threads, with its wider posterior gaping end extending just above the sea bottom surface to facilitate filter-feeding. Algae (e.g. Lobophora variegata ) and invertebrates such as sponges and encrusting corals tend to grow on the exposed part of the shell and may camouflage it very well.
The rigid pen shell can be found in coastal western Atlantic waters, ranging from southern Florida across the Caribbean and the West Indies to Brazil and the southern part of India. It is a benthic shallow water species and is typically found in soft-bottom silty habitats, with its narrow anterior end (umbo) burrowed down and attached to underground substrate by its byssal threads. Its wider posterior gaping end extends just above the sea bottom surface to facilitate filter-feeding. Algae, invertebrates such as sponges and encrusting corals tend to grow on the exposed part of the shell and may camouflage it very well.
The rigid pen shell burrows as it grows, but the wide posterior end of the shell always remains exposed so water from above the seafloor can be drawn through the inhalent chamber of the mantle cavity. Typical of bivalves, water is drawn over gills or ctenidium by the beating of cilia where oxygen from the water is absorbed. Suspended food and other water-borne nutrients also become trapped in mucus, which is then transported to the mouth, digested and expelled as feces. Unique gutter-like waste canals in the viscera of the inhalent chamber also help to keep gills and other organs clear from silt and other unwanted water-borne particules by expelling these as pseudofeces. [1]
Commensal symbionts such as crustaceans and a cardinal fish, Astrapogon stellatus , may be found sheltering inside the shell's mantle cavity. [2] This species is preyed upon by starfish, and other carnivorous gastropods, including the horse conch Triplofusus papillosus.
Scallop is a common name that encompasses various species of marine bivalve mollusks in the taxonomic family Pectinidae, the scallops. However, the common name "scallop" is also sometimes applied to species in other closely related families within the superfamily Pectinoidea, which also includes the thorny oysters.
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 (Mytilidae), and Dreissenidae.
Dreissena is a genus of small freshwater mussels in the family Dreissenidae in the class Bivalvia. They are found attached to firm substrates by threads from underneath the shells and are the only freshwater bivalves to attach to hard substrates in high densities while having a planktonic larval stage. They are considered the most aggressive freshwater invader in the world because of their ability to invade environments in every one of their life cycle.
The Rostroconchia is a class of extinct molluscs dating from the early Cambrian to the Late Permian. They were initially thought to be bivalves, but were later given their own class. They have a single shell in their larval stage, and the adult typically has a single, pseudo-bivalved shell enclosing the mantle and muscular foot. The anterior part of the shell probably pointed downward and had a gap from which the foot could probably emerge. Rostroconchs probably lived a sedentary semi-infaunal lifestyle. There were probably more than 1,000 species of members of this class.
Atrina fragilis, the fan mussel, is a species of large saltwater clam, a marine bivalve mollusc in the family Pinnidae, the pen shells.
Pinna is a genus of bivalve molluscs belonging to the family Pinnidae. The type species of the genus is Pinna rudis.
Atrina is a cosmopolitan genus of bivalve molluscs belonging to the family Pinnidae.
A bivalve shell is the enveloping exoskeleton or shell of a bivalve mollusc, composed of two hinged halves or valves. The two half-shells, called the "right valve" and "left valve", are joined by a ligament and usually articulate with one another using structures known as "teeth" which are situated along the hinge line. In many bivalve shells, the two valves are symmetrical along the hinge line — when truly symmetrical, such an animal is said to be equivalved; if the valves vary from each other in size or shape, inequivalved. If symmetrical front-to-back, the valves are said to be equilateral, and are otherwise considered inequilateral.
Mya truncata, common name the blunt gaper or truncate softshell, is a species of edible saltwater clam, a marine bivalve mollusk in the family Myidae.
Atrina squamifera, one of several species known as the horse mussel, is a species of bivalve pen shell. It is a marine mollusc in the family Pinnidae. It is endemic to South Africa.
Chlamys hastata, the spear scallop, spiny scallop or swimming scallop, is a species of bivalve mollusc in the family Pectinidae found on the west coast of North America from the Gulf of Alaska to San Diego, California. A limited number of these scallops are harvested by divers or by narrow trawls off the west coast of Canada.
Pteria colymbus, the Atlantic winged oyster, is a species of bivalve mollusc in the family Pteriidae. It can be found along the Atlantic coast of North America, ranging from North Carolina to Bermuda and Brazil.
Pinna carnea, commonly called the amber pen shell, is a species of bivalve mollusc in the family Pinnidae.
Atrina seminuda, the half-naked pen shell, is a species of bivalve mollusc in the family Pinnidae.
Arca noae or the Noah's Ark shell is a species of bivalve mollusc in the family Arcidae. It is found in the Mediterranean Sea from low tide mark to a depth of 60 metres (200 ft).
Crassadoma is a genus of rock scallops, marine bivalve molluscs in the family Pectinidae. It is monotypic, the only species being Crassadoma gigantea, the rock scallop, giant rock scallop or purple-hinge rock scallop. Although the small juveniles are free-swimming, they soon become sessile, and are cemented to the substrate. These scallops occur in the eastern Pacific Ocean.
Atrina zelandica, one of several species known as the horse mussel, is a large species of saltwater clam. It is found around New Zealand.
Laternula elliptica is a species of saltwater clam, a marine bivalve mollusc in the family Laternulidae, the lantern shells. It is the largest bivalve found under the surface of the seabed in the Southern Ocean.
Astrapogon stellatus is a species of ray-finned fish in the family Apogonidae, the cardinal fishes. It lives in the tropical western Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. It is commonly known as the conchfish because it typically conceals itself in the mantle cavity of a living queen conch by day.
Atrina pectinata is a species of bivalves belonging to the family Pinnidae.