Terebratalia transversa (Sowerby, 1846) 

Common lamp shell , transverse lamp shell, scalloped lamp shell

Synonyms: Terebratalia caurina
Phylum Brachiopoda
 Class Articulata
  Order Telotremata
Terebratalia transversa  photo taken at Rosario beach Marine Laboratory
Photo by: Anna Dyer, 08/02/02
Description:  The valves are broader than long.  As is the rule for members of Class Articulata, the hinge of this species cannot be opened fully without breaking the valves. The anterior opening undulates strongly, involving both valves. The pedicle valve (ventral) has a slightly elevated median ridge and a broadly rounded notch at the anterior margin opposite the pedicle.  The shell’s color may be gray, yellow, tan, brown, or reddish. Width up to 5.6 cm.

How to Distinguish from Similar Species:  Distinguished by location, color, and the fact that it is broader than long. No other brachiopod or clam in this region has such strong undulations in the anterior opening between the valves.

Note: Unlike in clams, the two valves of a brachiopod are dorsal and ventral. In this species the dorsal valve is smaller and underneath, while the ventral valve is larger, has the opening for the pedicle, and is on top so the animal normally lives "upside-down". The hinge is the posterior end of the animal and the opening is anterior.

Geographical Range:  Alaska to Baja California.

Depth Range:  It is found in the low intertidal zone but is more commonly subtidal to at least a depth of 1,800 m in clean, quiet water.

Habitat:  This species, when found, is usually attached to undersides or protected surfaces of large rocks.

Biology/Natural History:  The animal is solitary.  When it reproduces (in winter), the fertilized eggs develop into a characteristic 3-lobed and ciliated planktonic larva somewhat like a trochophore.  The larva does not feed (lecithotrophic).  The larva attaches and then develops into an adult.  Predators of this species include crabs, which chip off parts of the margin of the shell to reach the soft parts, and the seastars Evasterias troschelii and Orthasterias koehleri. The lampshell may survive crab attacks and many show asymmetrical shell growth from repairs that have been made.

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Dichotomous Keys:
  Carlton, 2007
  Kozloff ,1987, 1996

General References:
  Lamb and Hanby, 2005
  Morris et al., 1980
  O'Clair and O'Clair, 1998

Scientific Articles:

General Notes/Observations:

This species is often encrusted with coralline algae.  Photo by Dave Cowles, July 2000

This individual has unusually pronounced growth lines.  Shell found dead at 12 m depth near many live individuals off the Cone Islands by Jim Ramaglia, and provided by Andrew Rice.  Photo by Dave Cowles, July 2005.

Pedicle opening
This view of the under (dorsal) side of the animal shows the dorsal valve. At the top of the photo is the ventral (upper) valve with the hole from which the pedicle exits at the posterior end of the valve. The fleshy pedicle attaches to a rock, and the side shown here would be oriented downward in life. Note that the opening for the pedicle is at the very posterior end of the valve and the posterior end is not pointed. Photo of a 4.2 cm-wide individual by Dave Cowles, August 2020.

Life orientation
This is the normal orientation of the animal in life. The dorsal valve is down, and the larger ventral valve is up. The fleshy pedicle protrudes through the opening in the ventral valve seen on the right and attaches to a rock. Anterior is to the left and posterior to the right. Note that the ventral valve, which is on top and thus would receive more light, is encrusted with coralline algae in this photo while the corsal valve on the bottom is not. Photo of the same individual as shown for the dorsal valve above by Dave Cowles, August 2020.

This photo shows the hinge articulation.  The two valves are interlocking so that they cannot be opened more than in the picture without breaking. The fragile brachidium has already broken off in this individual. Photo by Dave Cowles

The set of brachial arms (brachidium) is a skeletal element which supports the lophophore. It is very fragile and usually breaks free when the animal dies or is disturbed. This photo shows a mostly intact brachidium. Photo by Dave Cowles, July 2020

Authors and Editors of Page:
Anna Dyer (2002):  Created original page
Edited by Hans Helmstetler  11-2002; Dave Cowles 2005-