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July, 2015


by Valerie

Poking around in ponds is one of my favorite activities. That mysterious world beneath the water's surface is populated by all manner of alien creatures and unusual plants. The fact that it is hidden from our human eyes, and we must expend a certain amount of effort to gaze into its secretive realms, makes it all the more intriguing.

Some of my earliest memories have to do with playing in the streams and pools around my home in Illinois. It was easy to learn about the fish, salamanders, frogs, snakes and turtles, as we had our library of little Golden Guide books that identified all these. There was even a volume called "Pond Life" and I practically memorized some of the pages. Besides the books, we also learned about our environment through the age old method of hands-on exploration. We caught all sorts of larvae, worms and anything else that looked remotely alive and kept them in an aquarium. A drop of water from the scummy bottom of a lake yielded incredible tiny organisms when viewed through the eyepiece of our microscope. Back in the days before computers and internet, when we had questions, and we often had loads of them, we checked our books or headed to the library.

There always seemed to be books that identified microscopic animals and algae, as well as adult insects such as water beetles, oarsmen, and water scorpions. Big insects were easy to figure out too; I knew from a very young age that hellgrammites turned into dobsonflies, and caddisfly larvae became adults that looked like moths with strange faces. But there were still numerous smaller insects and other things that were persistent mysteries. I don't think we ever knew what the white maggot-like larvae that grossed out my mother were (I now think they were probably horse flies), and we just made up a name for the flat round insects that clung to the bottoms of rocks. We called them chitons, although the creatures were arthropods that only superficially resembled the mollusks of that name; now I know they were beetle larvae called water pennies. That name never occurred to us, as they were much smaller than a penny and not all that copper-colored. I wondered why the horsehair worms that I put in my aquarium always died fairly quickly. It turns out that the adult worms have no mouths or digestive system, so they don't live very long, but I didn't learn this until decades later.

Some of the strangest things we found were the nondescript slimy or spongy globs that were attached to rocks and sticks. Some were undoubtedly freshwater sponges and others were types of algae. One kind that I definitely remember was not only a mystery, but a BIG one, and very unique. It was some sort of colonial animal (like a sponge or maybe a strange sort of waterlogged plant matter?) that ranged in size from marbles to softballs. The texture was firm but jelly-like. They reminded me of the fruits of Osage orange trees, but not so hard and definitely not that bright green. Maybe they were just very moldy and rotting fruits. These musings were about as far as I ever got in identifying the gelatinous balls. Then I left Illinois and the places that I played as a child. I went to college, had a career, traveled around, and moved to different places. I forgot all about the large slime balls in the ponds of the Chicago area.

Several decades later, I was attending a wedding in a lovely retreat with a lake near Dallas, TX. There was plenty of time to explore around the lake and, with digital camera in hand, photograph the mushrooms, insects and flowers in the area. While peering into the water, I saw something that caught my attention: some sort of round form with a pattern on it. It looked vaguely familiar but I couldn't place it. I pulled it out of the water and the memories flooded back. Here was one of the firm jelly balls that I used to find as a kid! With the insight and experience of many years, I could now tell that it was definitely a colonial animal, and bryozoans came to mind. This seemed an awkward fit, though, as I knew bryozoans by their common name of moss animals: very small creatures that coated pieces of driftwood on the beach with a network pattern. Even the fossil bryozoans that I had seen were flat and crust-like organisms, not big gelatinous spheres.

Of course, the internet came to the rescue and I was able to find out all sorts of illuminating data about what I now know is Pectinatella magnifica, commonly called the Magnificent Bryozoan or sometimes given the much more imaginative and descriptive name of Water Brains. Yes, the globs I used to find often had the vague shape and size of a brain but we always suspected they were some sort of "lower" animal like sponges or corals - nothing with a well-developed nervous system, so we never thought up that colorful moniker.

Water Brains are a distinctive species of freshwater bryozoan and are native throughout the eastern U.S. In recent decades, they have been found in places west of the Mississippi River, which accounts for why I found one in Texas. The animals can only live in warm, unpolluted water. They are filter feeders and the thick protein gel that surrounds them is a sort of exoskeleton that gives them structure. Each tiny animal in the mass is called a zooid. When conditions are no longer warm, wet or clean enough, the whole colony disintegrates and that's that. There is one detail, though, that makes these fragile organisms much more persistent: they produce the equivalent of seeds. The zooid grows a structure called a statoblast, which is a small grain with a bivalve shell of chitin and little hooks around the edge. This "escape pod" remains intact after the animal has disappeared, and it can withstand desiccation and temperature extremes. The tiny granules can be moved by animals, water or wind. When conditions are again favorable, the statoblast revives and grows into a zooid with the ability to start a new colony. In northern latitudes, the statoblasts explain why the bryozoans can survive the cold winters and also why they are most noticeable at the end of summer, after their colonies have had time to grow. It also explains why they can turn up almost anywhere.

It is wonderfully satisfying to solve a mystery, especially one that has lasted for many years. It is also nice to find a small segment of our environment that is not so familiar that everyone takes it for granted. The best thing, though, is that with each riddle solved, I will never run out of others, whether it be past curiosities I've all but forgotten, or future enigmas I have yet to discover.

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