Blue Zoo: Bryozoans

Featuring one amazing marine animal per week.

Bryozoans are tiny animals that live in colonies, and they are sessile, or attached to a solid surface. Most species live in the ocean but some are found in freshwater.

Bryozoans often encrust on other surfaces, such as kelp. Photo by Magdalena Almonrode-Rosario via Flickr, Creative Commons License. 

You may not have noticed bryozoans before. The individual animals, which are called zooids, are less than 1mm long. And although colonies of bryozoans are big enough to be seen, to most people bryozoans just look like a plant or some moss. However, once you know what to look for, they can be found in many places – such as growing on kelp!

They make up their own phylum, Bryozoa, and are part of a superphylum called Lophophorata, which also includes clam-like and worm-like organisms. All of these animals are filter-feeders that use a lophophore, a special set of tentacles, to collect food particles that drift by in the current.

The intricate patterns bryozoans make are better appreciated up close. In the middle of this photo is also a well-camouflaged nudibranch, which preys upon the zooids. Photo by   Ken-ichi Ueda via Flickr, Creative Commons License. 

Each zooid lives in a hard outer casing that protects it. It has an opening on the top through which the zooid can poke its lophophore when it feeds. Otherwise it retracts it inside the casing, which is known as the zooecium. Although a colony is composed of many separate zooids, they are connected by a fluid transport system. The zooecium has pores in it that allow all of the zooids to communicate.

Different species of bryozoans have diverse shapes and patterns. They can be very beautiful and intricate, like lace. When you look even closer, the protective zooecium can have interesting textures and even armor.

A microscope reveals the interesting patterns that occur on the hard, protective zooecium. Photo by Susannah Anderson via Flickr, Creative Commons License. 

Bryozoans are the subject of some very interesting and important research

Bryostatins are a group of chemicals being studied for use in cancer treatment, but they are very difficult to collect or create. Scientists discovered that one species of bryozoan, Bugula neritina, lives in symbiosis with special bacteria – and it turns out that those bacteria produce bryostatins. Efforts to clone some of the genes from these bacteria could make it possible to create bryostatin in amounts large enough to produce drugs for treating cancer.

Some species grow up and out instead of encrusting. Photo by Ken-ichi Ueda via Flickr, Creative Commons License. 

Because they make a hard shell, bryozoans are prominent in the fossil record. Photo by Grand Canyon NPS via Flickr, Creative Commons License. 

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