The Cambrian Explosion—in the Farmington River?

More than 500 million years ago, life on earth suddenly took a great leap forward. During the time known as the "Cambrian Explosion," multicellular life underwent a rapid expansion. The renowned Burgess Shale fossils record this as a period when many of the major groups of animals first appeared, including invertebrates such as corals, sea anenomes, sea stars, jellyfish, and soon after, bryozoans.

The bryozoan colony that herpetologist Brian Kleinman pointed out during a canoe trip on the Farmington River on Sunday was so strange looking I couldn't help but wonder if it wasn't some alien invader, or a disembodied brain, like one Dr. Frankenstein's assistant Igor might have dropped after robbing a medical school cadaver.



Brian Kleinman holds the bryozoan colony he found in a mucky channel along the banks of the Farmington River.

In fact, it was an ancient form of life rooted in the deep past, when much of the world would have been unrecognizable to us today. Where the river spilled into an impoundment was an example of one of the few freshwater species of bryozoan, Pectinatella magnifica.

Around the outside of this gelatinous colony, we saw what must have been hundreds of smaller rosettes, each comprised of a dozen or more individual animals. The inner area is filled with water that can be forced out with a gentle squeeze. Each animal has tentacles and beating cilia it uses to filter food particles suspended in the river's turbid waters and move them into its mouth.

"I love them," says Marcy Klattenberg, an ecologist and earth science teacher in Durham. "They can grow to over 12 inches across and include thousand of individual animals. This is the time of year when the colonies will soon form statoblasts [nodules or buds], which will then fall off and drift to the bottom where they will overwinter before growing into a new colony next spring."

As strange and primitive as they are, bryozoans like those found in Connecticut rivers, or the salt water of Long Island Sound, offer clues to a very different world, when life began its first great expansion some 500 million years ago.