Protist Love 2--Amoebas!

Life can surprise you.

A few months back, I left an old frosting cup out in the flower bed. It filed with rain water, and I forgot about it. A few days later, I noticed the water was bright green. So, I brought it into the lab, and I had been making periodic observations on the critters growing in it.

My some of my favorite are the amoebas.

Not too long after making observations, I observed this critter.

400x Phase contrast

I was excited because I recognized it from DJS Peterson’s Illustrated Guide to the Freshwater Protists, though I could not remember the name. Luckily, the book is in the library. It keys out as Amoeba radiosa. Unfortunately, but for cool reasons, this species does not actually exist. It turns out this is a common shape taken by amoeba as they float through the water column. When they find a new surface to adhere to, they revert back to whatever shape is normal for them.

Anyway, this cup is full of amoebas, and it is rather cool to see them moving along the slide. Amoeba don’t have discernable arms and legs, nor do they have a flagellum, a long tail-like structure some organisms use as a propeller or an oar. They move using pseudopodia. This is how it works: The amobae pushes tiny string-like structures called microfilaments against the cell membrane, which is like the amoeba’s skin, to form a pointed or rounded area. Cytoplasm, or the insides of the amoeba, flows into the space created by the actin. Basically, amoebas move their skin first and then their insides follow. I happened to get some images of this happening.

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Amoeba use their pseudopodia to feed as well. When they encounter something they might eat, they wrap their pseudopodia around it as if giving it a big hug. As Beautrice the Biologist says, "amoeba hugs are fatal."

Although I have observed amoeba beginning to engulf (or eat) something, I have not had the patience to fully observe it. However, I did come across amoeba, which has engulfed a pine pollen grain.

400x Bright field of an amoeba that has engulfed a grain of pine pollen.

Pine pollen is very recalcitrant, which means it is hard to eat or digest. I bet this critter had a stomach ache later.