Bryozoa

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Cheilostome Serpulid Cape Cod

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The Childrens Museum of Indianapolis - Evactinopora bryozoan - detail

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Bryozoa, also known as moss animals or ectoprocts, are a phylum of aquatic invertebrate animals. Typically found in marine environments, some species also inhabit freshwater. Bryozoans are most common in shallow coastal waters, where they often form encrusting or branching colonies on submerged surfaces, including rocks, shells, and seaweeds. Despite their small size, bryozoans play a significant role in aquatic ecosystems, contributing to habitat complexity and serving as a food source for other animals.

Characteristics

Bryozoans are characterized by their small, encased individuals called zooids. Each zooid is enclosed in a hard exoskeleton made of calcium carbonate, and they feed through a crown of tentacles, known as a lophophore, which is used for filter feeding. Bryozoans reproduce both sexually and asexually, with colonies growing through the budding of new zooids.

Classification

The phylum Bryozoa is divided into three main classes:

• Phylactolaemata: This class comprises freshwater bryozoans. They are distinguished by their gelatinous exoskeletons and a lophophore that is circular in shape.
• Stenolaemata: Marine bryozoans that typically have tubular zooids. This class includes the oldest known bryozoans, dating back to the Ordovician period.
• Gymnolaemata: The most diverse class, consisting mostly of marine species. Members of this class have a box-shaped zooid and a lophophore that is typically U-shaped or circular.

Ecology

Bryozoans are important components of marine and freshwater ecosystems. They serve as bioindicators, reflecting the health of their environment. Bryozoans can also be bioeroders, contributing to the breakdown of substrates in their habitats. Furthermore, they are part of the diet of various marine and freshwater species, linking them to the broader food web.

Fossil Record

The fossil record of bryozoans extends back to the Early Ordovician period, making them one of the oldest known animal phyla. Their calcareous skeletons make them well-preserved in the fossil record, providing valuable insights into the history of marine life and past environmental conditions.

Human Interaction

While bryozoans are not directly harmful to humans, they can impact human activities. They are known to colonize structures submerged in water, such as boat hulls and marine installations, leading to biofouling. This can increase maintenance costs and reduce the efficiency of affected structures.

Conservation

Bryozoans face threats from habitat destruction, pollution, and climate change. Conservation efforts are important to protect these species and maintain the health of aquatic ecosystems.