Freshwater and Marine Ectoprocts or Bryozoans: Ectoprocta

Ectoprocts are similar in appearance to corals, seaweeds, and sponges. They live in sessile (SEH-sill) colonies that resemble jellylike masses, crusts, cups, or plantlike structures. Sessile organisms are attached to one place and cannot move. A colony is any group of organisms that lives together. A single colony may be less than 0.039 inches (1 millimeter) high or grow as tall as 3.28 feet (1 meter). Depending on the species, the outer covering of the entire ectoproct colony is either jellylike or made of chitin ((KYE-tehn). Chitin is the tough, flexible material that makes up most of the external skeletons (exoskeletons) of arthropods (insects, spiders, and their relatives). Some ectoproct colonies are covered with a bony or calcified (KAEL-sih-faid) covering. Calcified coverings are made up mostly of minerals called calcium salts.

Individual animals are called zooids (zu-ihdz). Most zooids are so small that they must be studied through a microscope. Each zooid has a circular or u-shaped lophophore (LO-fo-for) surrounding a mouthlike opening. Lophophores have sticky tentacles covered in tiny bristles, or cilia (SIH-lee-uh). They help ectoprocts to breathe, eat, and protect themselves. Inside, they each have a body cavity, a single nerve bundle, and a u-shaped digestive system. In some colonies, all of the zooids are similar in appearance, but in others, there may be several different kinds. For example, some zooids spend most of their time eating. Others exist only to reproduce or to provide extra support for the calcified skeleton. In some colonies, a network of tubes connects the zooids to each other so they can share digested food.