Meet the Bryozoans

Bryozoan on my kayak paddle.                                                                      Photo: Nicole Reggia

In the world of biology, there is a plant, there is an animal, and there is a plant-animal. Specifically, moss-animals, the bryozoans.

I mention this because I recently had a run-in with these creatures while kayaking on a local lake. While moving across the lake, I saw something squishy, gelatinous and blobby near the surface of the water. After taking a few pictures, I was able to scoop one out of the water for further examination. fullsizeoutput_2f2f

The first thing it reminded me of was the brain in the science fiction movie Donovan’s Brain, because it looked just like the thing that scared the bejesus out of me when I was a kid.


After carefully placing Donovan’s Brain in a container with lake water, I took it home for further study and investigation. As it turns out, what I had was a giant freshwater bryozoan—Pectinatella magnifica, “the magnificent bryozoan”.  There are two interesting things about this species. The first is that out of the several thousands of species of bryozoans, they almost all grow in saltwater. The second is that this is a bryozoan here in my freshwater lake!  When starting a colony, an individual animal (called a zoid) hatches from a hard seed-like “statoblast” and the buds form a small number of identical individuals.  This foundling clump of zoids secrete a watery substance that hardens to form the firm gelatinous core where the colony spreads and reproduces. Bryozoans are not a coral but have evolved the same filter-feeding feature as corals. And, they’re really old–like 500,000,000 years old. And some have bizarre details of their biology that have helped them elude the best efforts of biologists to try and pin them down in the Earth family tree.

Bryozoan under observation.                                                                            Photo: Nicole Reggia

Bryozoans evolved in the Ordovician, the geological period that followed the Cambrian Explosion (my favorite), about 500 million years ago, about the same time as the corals they superficially resemble. Bryozoan are colonial or collective organisms not unlike a colony of bees. In some bryozoans, the individual animals specialize their function for feeding, defense or reproduction–much like honeybees. They can settle on virtually any immobile surface and several mobile ones: rocks, kelp, blades, or wandering hermit crab shells.

Bryozoan out of water.                                                                                     Photo: Nicole Reggia

Bryozoans are in their own little group as far as bilogical classification is concerned. They are so mystifying, both morphologically and genetically, that scientists can’t even seem to make up their mind whether the group belongs in the fundamental animal group the protostomes (insects, crustaceans, arthropods, water bears, and nematodes) or the deuterostomes (vertebrates, echiinoderms, and tunicates).

Finally, it’s worth noting that my bryozoan was found in a man-made lake in eastern Pennsylvania.  According to scientists, its presense is a good sign: one of high water quality.


Donovan’s Brain                                               Photo: Nicole Reggia