Range: Worldwide Habitat: Rocks, sticks, sand grains, wooden docks, and ice chunks Size: Up to 0.15 inches (4mm) as individuals; Up to 3 feet (91cm) as a colony Diet: Plankton Threats: Urchins, fish, sponges, and tunicates Life span: Theoretically indefinitely as a colony

Transcript:

Today on Animal Fact Files we’re discussing bryozoans. These animals are strange. They look something like a sponge or piece of soft coral, but they’re neither. In freshwater they appear in gelatinous blobs that might lead some people to wonder if they’re some kind of alien egg, but they aren’t aliens. Bryozoans are also known as moss animals - not to be confused with the moss piglets also known as tardigrades. From fresh, to brackish, and marine waters, the over 5,000 living species of bryozoans take up residence in water systems around the world.

These colony organisms have been observed from shallow waters to depths of over 5 miles (8,200 meters). They are often sessile, or unmoving, attaching to hard surfaces like rocks, sticks, sand grains, wooden docks, and even frigid Antarctic ice chunks! Some species do move, though these movements are often limited. There’s also a single known species that both moves and lives on its own, but for the most part these animals live in colonies.

Like the Portuguese man of war we’ve discussed previously, a single bryozoan colony is made up of many tiny animals that work together to form the entire bryozoa organism. The tiny individual animals that make up the bryozoa colony are called zooids. They max out at 4 millimeters in size and have a body topped by circular or horseshoe shaped tentacles and surrounded by an outer casing into which they can hide if startled. This works as an anti-predator defense. Some species also possess the ability to produce toxic chemicals or are covered in harmful spines to deter predators.

Predators to bryozoans include urchins and fish and they can be overgrown by other animals like sponges and tunicates. The zooid’s tentacles are covered in tiny hair-like structures called cilia that circulate the surrounding water. This creates a current that draws food towards the zooid’s mouth. Bryozoans eat plankton particles. They have a U-shaped digestive system with an anus that’s separate from their mouths.

Some of the zooids in the colony don’t eat, their job may be keeping the colony attached to a surface or reproduction, but they still obtain nutrients because the whole colony is connected. They may be connected through fibrous cords of tissue or pores in their bodies that allow exchange of body fluid. It just depends on the species! How long individual zooids may live is tough to determine, however, an entire colony may theoretically live indefinitely.

These animals produce both eggs and sperm, though typically at different times in order to avoid self fertilization. Many species brood their eggs and then release the free-swimming larvae once the eggs hatch. These larvae find a spot to settle and, once settled, reproduce asexually through budding - which is when a clone of the original organism develops from a growth off the parent. The colony itself will then just continue to grow from there. Sometimes they break apart due to extreme weather or predators but the pieces are able to keep on living after this, which is why they have somewhat of an indefinite lifespan!

Some bryozoans, look like gelatinous blobs, others look like a crust forming over a hard surface, and others look like branching twigs or fans. While the individuals that make up the colony are tiny, they colony itself can reach more than three feet (91cm) in length in some species! Have you ever seen one of these animals in the wild?

For more facts on bryozoans, check out the links in the description. Thank you to Michael for today’s request! Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files!