By LESLIE BISHOP, guest columnist
This time of year mysterious objects reveal themselves in ponds and lakes.
I have heard numerous names from friends and neighbors: Giant Blob, Alien Brain and Jelly Ball. All are appropriate descriptors of the slimy, translucent masses.
With a closer look, you can see each mass is defined by a beautiful design of individual facets each rimmed with moving tentacles.
Indeed, our blob is a living organism, a colony of freshwater bryozoans with the apt scientific name, Pectinatella magnifica, or the “Magnificent Bryozoan.”
Each individual in a bryozoan colony is a tiny animal, called a zooid, whose body resides in a compartment surrounded by a protective case.
Some bryozoan species secrete a leathery or threadlike calcified case, but the Magnificent Bryozoan secretes a dense gelatinous substance that adheres to fallen tree branches or plants under water.
As the colony grows, the zooids secrete more jelly to the inside of the mass that creates more surface area for individuals to live. The mass grows through the summer to reach up to 3 feet in diameter and may be round or oblong.
Even though the zooids live together in a colony, they are responsible for feeding themselves. Each zooid has a crown of tentacles covered in tiny hairs, or cilia, that move rhythmically to create a current bringing small particles such as bacteria, protozoans, and algae toward the mouth. When zooids are undisturbed, their tentacles are expanded with the appearance of tiny flowers in constant motion. With the slightest movement in the water, all the zooids instantly retract their crown of tentacles into their body cavity. It takes a lot of patience to observe these peculiar animals feeding!
As temperatures decrease during the fall, the colony begins to disintegrate and die. During this time, the colony produces thousands of structures called statoblasts that are washed from the jelly surface as the colony dies.
Statoblasts, a type of survival capsule, are resistant to freezing and provide a way for the bryozoan to be dormant until spring brings the return of favorable living conditions. The statoblast then can germinate, giving rise to a new colony.
The Magnificent Bryozoan has a distinct type of statoblast that floats and is covered in flattened barbed spines. The spines can latch onto a duck or goose that visits the pond and hitchhike to another pond.
What I find fascinating about bryozoans is that they are an excellent example of a group of animals that was more diverse in ancient times than it is today. We usually think of the evolutionary process as increasing species diversity through time, but bryozoan diversity has decreased.
Thus, to enjoy bryozoan diversity, you need to be a fossil hunter! You can find bryozoan fossils that are abundant in limestone from the Ordovician layers throughout southern and eastern Indiana. Some of these bryozoan fossils look like branching coral, and others encrust shells of clams or snails.
From their 500-million-year-old fossil record, 15,000 species of bryozoans have been identified.
Today, there are only about 5,000 living species. The majority live in oceans and only 50 species live in fresh water, like our Magnificent Bryozoan.
August and September are the best times to look for Magnificent Bryozoans because they are reaching their maximum size. Check out your neighborhood ponds, as well as Yellowwood Lake and Lake Monroe, for giant floating blobs of bryozoans.
If you see them, be glad, for they indicate clean and unpolluted water.
Aliens from Mars? Maybe not, but they remain an unusual and intriguing part of life in the pond.
Leslie Bishop is a Brown County resident and retired biology professor from Earlham College. She is a volunteer interpretive naturalist at Brown County State Park. She can be reached through the newspaper at firstname.lastname@example.org.