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Excuse me, Sir. There's a Moss-animal in my Lake

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In the world of biology, there is plant, there is animal, and there is plant-animal. Specifically, moss-animals, the bryozoans.

I mention this because someone in Virginia recently had a run-in with these creatures that was startling enough to result in a press release. And when a bryozoan generates a press-release, that is in itself kind of news-worthy.

It all started when someone in Newport News, VA, was out walking their boss's dog in October and discovered something floating in a man-made lake. Something squishy. Something blobby. Something alive. Though this isn't the same specimen, here is a youtube video that shows what you might have seen had you been walking the dog that day.

After much scratching of heads and exchanging of emails by scientists at the Virginia Marine Institute at the College of William and Mary, the blob was deemed a giant freshwater bryozoan -- Pectinatella magnifica, "the magnificent bryozoan". There are two interesting things about this: 1. It's a freshwater bryozoan -- they almost all grow in saltwater. And 2. it's a bryozoan! Bryozoans are like the whales of the coral world -- they are not coral, but have evolved into the same filter-feeding polyp-like niche. They're really old -- like 500,000,000 years old. And some bizarre details of their biology have helped them elude the best efforts of biologists to try and pin them down in the Earth family tree.

Bryozoans evolved in the Ordovician, the geological period that followed the Cambrian Explosion about 500 million years ago, about the same time as the corals they superficially resemble. Bryozoa are colonial or collective organisms not unlike a colony of bees, Volvox, or marine salps. Each individual colony member is a little animal that sometimes secretes a calcium carbonate shell that fuses with that of those all around it. Others, like our magnificent bryozoan, are mostly jelly and water (the latin name Pectinatella is a good clue to this).

The little animal – adorably called a zooid – is very simple: it has a U-shaped gut and a crown of ciliated tentacles called the lophophore that it can evert to feed. The cilia on the tentacles beat to draw in food, an effect you can see vividly at about 1:35 in this stirringly-(for bryozoa)scored video, after lophopher eversion at about :42. Here's a different look. The mouth is inside the ring or horseshoe-shaped crown. A simple body cavity, a secreted protective coating, a few nerve and muscle cells, and perhaps an ovary and/or testis is about everything else there is. To breathe, the zooid exchanges gas through the large surface area created by its ciliated tentacles. To excrete waste (the equivalent of urine, which in vertebrates is collected by the intricate structure of the kidneys), it does the same.
 
 

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