Phylum Bryozoa

The bryozoans may well be the most widely distributed and speciose phylum of animals that you have never heard of. Known as the lace corals or moss animals, they are found in freshwater and brackish water as well as all the world's oceans.

Lace corals are mostly social organisms, although one genus contains only solitary individuals. Like the brachiopods, they possess a horseshoe-shaped feeding organ, the lophophore, but whether this reflects an evolutionary relationship or is merely a result of convergent evolution is still being debated.

I really first learned about bryozoans when I started teaching invertebrate zoology. The more I learned about them the more fascinated I became. I also thought back to the hubris of youth. When I started teaching at the University of the South Pacific my boss was Professor John Ryland - a world expert on bryozoans. I used to tease him about working on a backwater phylum and instead of learning about them from him, pursued other interests. I now regret that. I mean these things are crazy - it's like they are from another universe. How's this for starters? The individual bryozoans are called zooids and their bodies are made up of two parts: the cystid, that produces the body wall plus the exoskeleton (which can be chitinous or calcareous) and the polypide which contains the digestive system, the lophophore and pretty much all the structures of the animal. Here's the crazy thing - when the polypides fill with waste products, the cystid destroys them and grows a new polypide. It's kind of like our skin destroying and then regrowing all of our internal organs after we fill up with feces.

There are around 5,000 extant lace corals with a further 15,000 known from the fossil record. Most species are tiny, with individual zooids only reaching 0.5 mm or so, but the colonies themselves can be a meter or more across depending on the species.

The Wikipedia entry on these fascinating animals is particularly comprehensive and I direct you there for further information.

Unidentified bryozoan 1

Unidentified Bryozoan Species 2

Unidentified bryozoan species 3