Lampshells: Brachipoda

Lampshells live as individual animals. Their bodies are completely enclosed, above and below, by a pair of shells. Each shell is called a valve. The phylum is divided into two distinct groups, or classes. In class Inarticulata, the valves are not hinged together. Instead, muscles keep them together. In the Articulata, a special tooth-and-socket hinge joins the valves. The valves of individual lampshells are usually different sizes. The largest valves measure 0.039 to 3.54 inches (1 to 90 millimeters) across, and the outer surface is smooth, pitted, or spiny.

Nearly all lampshells are sessile (SEH-sill). Sessile animals attach themselves to surfaces and cannot move. Lampshells attach themselves to solid surfaces by a soft, flexible stalk, called a pedicel (PEH-dih-sel). The pedicel is part of the body wall and is connected to the lower valve. A few species with pedicels either do not attach themselves to anything or anchor themselves in loose sand so they can still move around. Species without pedicels glue themselves directly to objects.

Lampshells have crownlike ridges with sticky tentacles that surround the mouth. The lophophore (LO-fo-for) is used to help them to breathe, feed, and protect themselves. It is also used to remove body waste from inside the valves. The lophophores are circular, u-, or spiral-shaped. The body wall has special tissues that form the mantle lobes. The mantle lobes make the valves. They have an internal body cavity. The digestive system is u-shaped and may or may not have an anus. The nervous system includes two groups of nerve cells, one in front of, the other behind the mouth. A ring of nerves surrounds the upper portion of the digestive system, with nerves leading into each of the tentacles of the lophophore. The open circulatory system carries clear blood. The blood in open circulatory systems does not always stay inside of tubes, or vessels. Kidneylike organs help to remove waste from body fluids. They are also used to release eggs or sperm into the water.