#pelomyxa

"Pelomyxa are giant amoeba, capable of growing as much as 5 millimeters in length. So it doesn't seem like they should be that difficult to find. In fact, Jame--our master of microscopes--found hundreds of them filling up his pond tank, completely visible without the help of a microscope. They were so large that he actually took one and touched it. So, if you would like to know what it feels like to pet an amoeba, he is now an expert. He says, "It's squishy.""

Journey to the Microcosmos- The Microbe That's Big Enough to Pet

Images Originally Captured by Jam's Germs

cc: "I will occasionally have an argument with my four year old about the size of microbes. We'll look under the microscope and at a mere 40x magnification, whatever we're looking at might fill the whole view, I will shout "It's huge" and he will retort "it's tiny!" and then we will laugh because, of course, we are both right.

Journey to the Microcosmos- Bursaria: Giant Gravity-Sensing Vacuums

Images Originally Captured by Jam's Germs

"Scientists have been observing unicellular organisms doing this for centuries. There are a few different ways microbes move through their environment. They may move in response to sensing chemicals, which we call chemotaxis. They might move in response to light, which we call phototaxis. Then there's moving in response to sensing gravity. Maybe you have a guess at what that might be called... gravitaxis."

Journey to the Microcosmos- Bursaria: Giant Gravity-Sensing Vacuums

Images Originally Captured by Jam's Germs

"When a microbes is traveling down but not swimming, it is sedimenting. Scientists measure the sedimentation rate of microbes by immobilizing them and watching them fall through water. Using that method, they've found that the sedimentation rate of Paramecium tetraurelia is about 67.4 micrometers per second, and the sedimentation rate for Paramecium caudatum was about 123 micrometers per second. So that gives you a baseline for some ciliates."

Journey to the Microcosmos- Bursaria: Giant Gravity-Sensing Vacuums

"But while they may be in our pond tank, they're often harder to pick out with a microscope. They move incredibly slowly, and their cytoplasm tends to fill up with grain of sand and other particles, so they often blend into the background with the other debris we find in our slide. So despite being giants, the pelomyxa can be deceptively difficult to recognize. And as we will see, that is not the only trick thing about them."

Journey to the Microcosmos- The Microbe That's Big Enough to Pet

Images Originally Captured by Jam's Germs

CC: "But it's lovely to think of the Pelomyxa--our very own mysterious, hidden giant--helping to undo some of the myths that we hold about simplicity and evolution. It's not the sort of story that gets passed down through generations, but you know, maybe it should be."

Journey to the Microcosmos- The Microbe That's Big Enough to Pet

Images Originally Captured by Jam's Germs

CC: [P]elomyxa are so large that, even with our lowest magnification, we can't show an entire one in one shot. This image was created by stitching together a bunch of photos of this roughly 2mm Pelomyxa.]

Journey to the Microcosmos- The Microbe That's Big Enough to Pet

"That might sound like an odd way to describe eating until you realize that Pelomyxa eat by just engulfing stuff around them. And when you're a giant amoeba living at the bottom of a pond, the stuff around you is sludge. Lots of pond sludge, though if you want to get technical about it, that sludge is called sapropel. And while sludge may not sound particularly delicious, sapropel is made up of decaying organic matter. It is rich in nutrients, making it a feat for amoeba and endosymbionts alike. So while calling them a sewage treatment plant may not seem the most glamorous comparison, it is a life that probably works well for all microbes involved."

Journey to the Microcosmos- The Microbe That's Big Enough to Pet