While crayfish may win the award for most lots in the NCSM NMI collection, the group bryozoans is a little bit harder to quantify. Considering there are about 5,000 known species living today, we have comparatively few lots actually representing the phylum Bryozoa – the real trick is: how many lots contain bryozoans? This is a loaded question. To answer it, we first need to know what a bryozoan is!

Bryozoans are also refered to as moss animals and are called that for a reason. First off, they are colonial, which means there are many individuals physically connected to one another. The zooids (the individual animals that make up the colonies) are quite small whereas entire colonies can be quite large. Finally, they have a ring of tentacles (the lophophore) surrounding their mouth, and a U-shaped gut. When all the lophophores in a colony are extended, they look like a soft and delicate underwater moss to the naked eye…that has thousands of little mouths and feeds on tiny plants in the water column. You can imagine that under the microscope, their uniqueness really shines.

bryo image summary
Illustration done by Megan McCuller, NCMNS NMI.

The need for a microscope is why bryozoans were lumped with other groups including corals and plants (together called the corallines) in the 1700s. Linnaeus in the mid-1750s coined the term Zoophyta – animals which cannot move and resemble plants. In the early 1800s, multiple researchers with the aid of a microscope independently recognized distinguishing characters between zoophytes, such as having ciliated tentacles and both mouth and anus. As a result, the terms Polyzoa and Bryozoa were both in use. A separation of Bryozoa was proposed a few years later: Ectoprocta (anus outside the ring of tentacles) and Entoprocta (anus inside the ring of tentacles). While today Entoprocta (also known as Kamptozoa) is regarded as a separate group, bryozoans can still be referred to by three different names: Bryozoa, Polyzoa, and Ectoprocta, with Bryozoa being the most widely accepted. If you ask us… the taxonomists who study bryozoans just don’t want to consider themselves ectoproctologists!


There are 3 classes within the phylum Bryozoa: Phylactolaemata, Gymnolaemata, and Stenolaemata. Phylactolaemata includes all the freshwater species, including the blob-like species Pectinatella magnifica that we have posted on our Facebook page about. Both Gymnolaemata and Stenolaemata are saltwater groups. The stenolaemates and many of the gymnolaemates have a hard skeleton that protects the soft tissue of each zooid. There is a huge variety of growth patterns within each of the 3 classes: raised domes, encrusting sheets, arborescent (branching like a tree), creeping (like a vine), ruffled masses, and squishy blobs. However, when it comes down to species (at least in the marine groups), there’s a lot of uncertainty. This is due in large part to the fact that species can change in response to the environment! For instance, if there are sea slugs that eat the bryozoan, it may develop spines in response to deter feeding. A taxonomist (someone who studies the classification of organisms) must consider whether the spineless and spined colonies are actually of the same species.

So let’s bring it back to the NCSM NMI collections… Bryozoans live in most marine environments and grow on many different things (rocks, coral skeletons, barnacle shells, algae, crab exoskeletons, plastic, etc.). This means that despite not having many jars specifically labeled “bryozoans”, we likely have many jars that, by coincidence, have bryozoans in them! How will we know? By keeping a sharp eye out for any specimen with a crust or branching thing growing! And as we find them, we will be sure to keep y’all posted.

by Megan McCuller.

freshwaterbryozoan copy
Freshwater Bryozoan. Photo courtesy of Andie Woodson, NCMNS NMI Unit.

Thanks for reading our Bryozoan Creature Feature! Please tell us what you think in the comments, and if you enjoyed what you read, share it with your friends and follow us on Instagram (@bwwilliamslab)!

Leave a Reply

Your email address will not be published. Required fields are marked *