Jewel Box Clam (Pseudochama exogyra)
Contributed by TPERP Kirk Copic
Left Handed Jewel Box Agate Jewel Box
Pseudochama exogyra Chama arcana
Where to find them: They attach to the sides of boulders. They are found in the mid-tidal zone and often live in large clusters along with other clams and tube snails. There are many different types of JBCs; the species that live in our tidepools are found as far north as Oregon and extend south into Baja California.
What’s their life like: The name bivalve is derived from the pair of hinged valves (shells) that surround the body. Jewel Box Clams have a two-part hinged shell that protects a soft invertebrate inside and can grow to be about 5 centimeters. The shells are white and thick with two distinct halves (this differs from most clams, which have symmetrical shells); the right valve is in the shape of a box and the left valve forms the lid.
What do they eat: Most bivalves are filter feeders, using their gills to capture particulate food, such as phytoplankton, from the water.
Who eats them: Sea stars and octopuses
Adaptations: The shape and surface of the valves helps to promote the growth of small plants and animals on it. This growth on the shells provides some camouflage protection from the JBCs main predators, sea stars and octopuses. Like fish, bivalves breathe through their gills. They have adapted to take in food through their gills as well, since they lack a head, jaws and an external mouth. They are called filter feeders because they filter their food through the water they take in.
Reproduction: They reproduce by external fertilization of the eggs and then the embryos develop in two separate stages in the water column before settling to the bottom to attach.
Interesting facts :The JBC fixes itself permanently onto rocks or other solid objects using its foot that extends outside the shells.
The Chama genus is the only surviving clam from a group of clams dating back 200 million years. They may be an intermediary step between two extinct families of the Chamacea superfamily.
Sometimes they are confused with oysters. They are similar but not the same as oysters.
Scientific name: Pseudochama exogyra
Common name: jewel box clams
Last revised 08-Aug-13