The oyster crab is a very small crab that ranges in color from pale orange to a shade of yellow that is so light that it is nearly white. Zaops ostreus is the Latin name for this species of crab, which is from the Pinnotheridae family. The crab has translucent body parts. Oyster crabs get their name from the place where they live — inside the gills of a clam or oyster.

As an oyster crab has to live within the body of another kind of shellfish, it must be very small. An adult specimen from this species is usually no larger than half an inch (1.27 centimeters) across. This tiny crustacean has very few natural defenses. In fact, its key line of protection is the shell of the oyster or clam in which it resides. Its food source also comes from the oyster or clam that protects it. It does not eat the clam or oyster that it lives inside but ingests some of the food that the larger shellfish collects for its own nutrition.

Oyster crabs are most commonly found in shellfish that live in the Atlantic Ocean, particularly in northern waters. The incredibly small crab as consumed as a delicacy and are added to stews and sometimes omelettes. Sometimes this kind of crab is considered to be a "baby" soft shell crab. As the oyster crab is not easy to fish for and because of the incredibly small size of the shellfish, it is an expensive ingredient and is not always easy to find.

Some plants that process clams and oysters do not even bother to harvest any oyster crabs that the come across during the shucking process. Sometimes the crabs are simply found as a sort of culinary surprise when they are opened by chefs. For this to happen, the clams or oysters have to be shipped live to the restaurant kitchen. There are some companies that also ship life shellfish to individual home cooks who love preparing gourmet food. In this case, there is also the opportunity for a surprise oyster crab.

Because this kind of crab is so rare, there are few recipes that call for them. One of the best ways to bring out the flavor is to simply saute them in butter. The flavor of the crab is sometimes compared to the flavor of shrimp.