Atrina rigida

Taxobox
name = "Atrina rigida"


image_width =
regnum = Animalia
phylum = Mollusca
classis = Bivalvia
ordo = Pterioida
familia = Pinnidae
genus = "Atrina"
species = "A. rigida"
binomial = "Atrina rigida"
binomial_authority = (Lightfoot,1786)
synonyms = "Pinna rigida"

"Atrina rigida", commonly known as the rigid pen shell, is a bivalve mollusc found from the North Carolina coast through the West Indies and to Brazil. It has attracted research interest in studies of calcification in its nacre as well as other aspects of its ecology.

Description

As is typical with the Pinnidae, the shell is elogated and wedge-shared, coming to a point at the anterior end. There are fifteen or more ridges running lengthwise, and spines arise from these towards the posterior edge. The exterior of the shell is an olive brown. The interior is nacreous to about half its length, and there is a conspicuous scar in the center of the shell at the border of this area, where the posterior adductor is attached. The mantle of the animal is orange and does not fill the shell entirely. The similar "A. seminuda" has the adductor scar entirely within the nacreous area.

"A. rigida" may grow to 30 centimeters in length, though typical specimens are somewhat shorter.

Ecology

Like most pen shells, "A. rigida" lives in soft bottoms, with the majority of the shell buried, point down, leaving only a few inches exposed, held in place by an extensive net of byssal threads. This pen shell tends to prefer shallower waters, whereas related species prefer greater depths.

It is a filter feeder, taking in water and nourishment through the gap between the valves at the posterior (upper) edge. Commensal crustaceans may live in this opening, apparently feeding upon excess food; barnacles and other creatures may attach themselves to the exposed exterior of the shells.

This species is preyed upon by the horse conch ("Pleuroploca gigantea").

"A. rigida" is noted for its ability to heal breaks and holes made in its shell.

Uses

Pen shells are harvested locally for food, especially along the Mexican coast; the large posterior adductor is similar to the meat of the scallop. Black pearls are produced which are suitable for jewelry.

Scientific interest is the species is extensive. Of late it has been the subject of molecular biology studies of its calcification enzymes and its myosin. It is also studied due to its regenerative capabilities and for the ecology of its commensal crabs and shrimp.

References

*cite web
url = http://www.enature.com/fieldguides/detail.asp?recnum=SS0004
title = Stiff Pen Shell
publisher = eNature.com
accessdate = 2008-02-01
*cite book
title = The Living Marine Resources of the Central Western Atlantic
publisher = American Society of Ichthyologists and Herpetologists
editor = Carpenter, Kent E.
date = 2002
url = ftp://ftp.fao.org/docrep/fao/009/y4160e/y4160e00.pdf
accessdate = 2008-02-01 p. 79
*cite web
url=http://www.gsmfc.org/seamap/picture_guide/Bivalves/atrina.pdf
title = Guide to Shelf Invertebrates - Gulf of Mexico: Family Pinnidae
accessdate = 2008-02-01
*cite journal
last = Grave
first = Benjamin H.
title = Anatomy and Physiology of the Wing-Shell Atrina Rigida
journal = Bulletin of the Bureau of Fisheries
volume = xxix
date = 1909
url = http://books.google.com/books?id=AEJMAAAAMAAJ&printsec=titlepage&dq=atrina+rigida
accessdate = 2008-02-01
*cite web
url = http://www.mitchellspublications.com/guides/shells/articles/0046/
title = American Stiff Pen Shell: Strength and Rigidity
last = Mitchell
first = Patricia B.
accessdate = 2008-02-01