Moss animals are not from outer space

Last summer I was walking along the banks of the Rock River near Byron when I observed a mass of protoplasm that looked like a large glob of gelatin encircling a stick in shallow water near the shore. I knew immediately that it was neither an alien form of life dropped by some UFO scouting out the Rock River Valley, nor was it a mutant form of life developed by radioactivity from the nearby nuclear power plant. It was a colony of primitive animals named Pectinatella magnifica, belonging to the animal group named Ectoprocta (outside-anus), or more familiarly called the moss animals or bryozoans.

When I taught biological science at the university, hardly a year passed that a student did not bring in a specimen of Pectinatella wanting to know what it was. Usually the gelatinous glob was small enough to fit into a quart fruit jar, but on one occasion a student bought in a bucket containing a specimen as large as a basketball. It was difficult for the non-biology major to believe that this amorphous mass had been secreted by thousands of tiny animals living in close association with each other in a mutualistic relationship.

The moss animals are a primitive and ancient group with fossils dating back some 500 million years ago to the Upper Cambrian period of geological history. There are about 4,000 different species of bryozoans living today, most of which are found in the marine environment in which they evolved. A few, like Pectinatella (“The Blob,” to many biologists) made the transition to brackish and fresh water. “The Blob” is always attached to some solid object, frequently anchoring itself around a stick and can be found in fresh water streams and ponds throughout the United States and southern Canada.

The basic ground plan of moss animals seems to suggest an affinity with the much more primitive corals, but the two belong to entirely different animal phyla. Though the two groups are structurally quite different, it can be said that they are ecological analogs in that they share the same basic mode of life.

If one closely examines the outer surface of the gelatinous mass, he will notice the surface is etched with many rosette-like markings. Each of these rosettes contains many separate individuals termed zooids. Each zooid whose job it is to gather food has a rather unique device called the lopohophore (tuft-bearing), which bears a ring of tentacles that are constantly in motion, creating a current that brings in all types of food items, both living and dead.

Some moss animals have members of the colony that are the strangest of all “freaks of nature.” These zooids afford protection to the feeding individuals and resemble the head of a vulture with an attached flexible neck. These guardians of the colony are appropriately named avicularia. Like an army of alert scouts, they keep their heads moving about in all directions, and with wide-open jaws snap vigorously at any intruding enemy, holding them with bulldog tenacity and eventually killing them. Many of these crushed intruders are then swept into the mouths of the feeding zooids by the current created by the lophophores. I certainly would not relish a swim in an area with moss animals if these vulture heads were as large as they are ferocious.

It is reported that the gelatinous base of these colonies is toxic to fishes, but I cannot find a specific reference regarding the nature of the toxicity.

Moss animals reproduce both sexually by forming sperm and eggs and asexually by budding. They are usually hermaphroditic in that both ovaries and testes are found in the same individual, but self-fertilization does not occur. Nature ensures that in most hermaphroditic forms there are provisions made for cross-fertilization with another individual’s reproductive cells. Variations in the genetic material of each individual are thusly shared.

The little-known moss animals or bryozoans of the animal kingdom are interesting creatures that fill a specific niche in the environment they occupy. If you happen on one of their colonies while communing with nature, appreciate their complexity and don’t believe they came from another planet or that they are a biological warfare agent planted by a terrorist.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960-1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

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