Bryozoer

Bryozoer, or bryozoans, are a phylum of small aquatic invertebrate animals. Most species form colonies composed of many individual units called zooids that live together in a shared exoskeleton. Each zooid functions as its own animal, primarily feeding and maintaining the colony. Bryozoans are filter feeders that extend a crown of ciliated tentacles known as a lophophore to capture suspended particles from the water.

Colonies vary in form, being encrusting, branching, or stalked, and they attach to substrates such as rocks, shells, seaweeds, or man-made surfaces. The colony’s skeleton is often mineralized, made of calcium carbonate, though some species have weakly mineralized or flexible skeletons. Within a colony, zooids can specialize for feeding, defense, or reproduction, yet they remain genetically identical members of the same organism.

Feeding is carried out by the lophophore, which creates water currents and captures microscopic plankton and detritus. Reproduction occurs both asexually, by budding to expand the colony, and sexually, producing free-swimming larvae that settle to form new colonies. Freshwater bryozoans can produce statoblasts, resistant dormant stages that help them survive adverse conditions.

Ecologically, bryozoans contribute to habitat complexity and can form reef-like structures in some regions. They are found in marine and freshwater environments worldwide, from shallow littoral zones to deeper waters. Their long fossil record, with diverse colony morphologies, makes them valuable in biostratigraphy and studies of past ecosystems. Taxonomically, Bryozoa is sometimes treated within varying classifications, but they are broadly recognized as a distinct, colonial, lophophorate phylum.