Bryozoans (Moss Animals)
Bryozoans are microscopic aquatic invertebrates that live in colonies. The colonies of different species take different forms. Most are attached to a structure such as a rock or submerged branch. Some colonies are rounded, jellylike masses. Others resemble antlers or mosses (bryophyte means “moss animal”), trace delicately like vines across rocks or create furry colonies. The species that creates the round, jellylike masses is Pectinatella magnifica.
Each tiny individual bryozoan (zooid) is attached to a surface at its base. Its body has an outer sleevelike structure (cystid) and a mass of organs (polypide) that moves within it. An opening at the top of the cystid permits the polypide to slide outward toward the water, exposing a headlike structure (lophophore) crowned with tentacles, which filter food from water. At the slightest disturbance, the polypide and tentacles retract instantly.