A Star Shaped Amoeba w/Video

Images made through a microscope. All subject types.

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Mitch640
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A Star Shaped Amoeba w/Video

Post by Mitch640 »

I have been looking for one of these guys for weeks. This is the first one I have found, although I have seen pictures of them. I got this from a Petri dish I had put some moss in and enough creek water to cover the moss, then let it grow for a week or so. It has been producing some great subjects.

He is also being pestered by a whipping Nematode blundering through.

I have some great video of the Star. I have posted the link on my YouTube. For some reason, the T1i does better video than stills.

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This seems to be a different strain of amoeba, that I have not ID'd yet. He is like a moving junk pile, and I saw a few of these in the water.
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Ferry
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Post by Ferry »

Hi Mitch,

A star-shaped amoeba is an amoeba in its floating form, caused by disturbing. It can stay in that shape for hours. At least it changes to its normal locomotion form like the small limax-shaped amoeba which passed below. You can't use this shape for determination.
Did you notice the third amoeba, disc-shaped and covered with a little debris which passed underneath the star-shaped one (in the video)?

Best wishes,

Ferry

Mitch640
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Post by Mitch640 »

Thanks for the information Ferry.

I did see the little one below the star. In fact, there were a number of those in the sample and was the first form I did see. There seemed to be a number of different kinds. They are so interesting, that I think I am going to do some amateur study of amoebas as I go along. They are very entertaining animals.

In fact, when I first heard about them in school, it crossed my mind, that the very first amoeba that ever developed, is still alive. They multiply by dividing and before long, there are so many of them that even a large natural disaster could not kill them all. So, by definition, one part of that very first amoeba is still crawling around. ;)

john sp.
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Post by john sp. »

Hi Mitch, you've got a lively collection of protozoa in your sample, there. Quite a variety of ciliates and amoeba swimming about.

Thanks, Ferry, for the comment on that star-shaped form being typical for some amoeba when they are free-swimming and not attached to any surface. I was unaware of that.

John

Mitch640
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Post by Mitch640 »

John, this collection of moss, I have 4 different kinds, collected in the woods, is turning out to be a goldmine for everything from water bears to ameoba, and a lot of stuff in between. Being new to this, I was kind of worried that it would be hard to find subjects when the hard freeze comes this winter, but it's not going to matter. Between the moss, which I can collect any time, and my toilet bowl scrapings, I have plenty to look at. LOL

I have found this site that gives some help with identification of amoeba's and explains the free swimming stage.

http://amoeba.ifmo.ru/guide.htm

rjlittlefield
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Post by rjlittlefield »

Mitch640 wrote:In fact, when I first heard about them in school, it crossed my mind, that the very first amoeba that ever developed, is still alive. They multiply by dividing and before long, there are so many of them that even a large natural disaster could not kill them all. So, by definition, one part of that very first amoeba is still crawling around. ;)
It's an attractive thought, but the world doesn't work that way.

The average amount of ancestral material in each amoeba drops by half each generation, being replaced by newly assembled atoms. Once the population gets large enough to become stable, the total amount of ancestral material in all amoebae combined also drops by half each generation, the remaining part being lost to individuals that die.

This gives us a classic decay model, with a "half life" of one generation.

Using that decay model, and estimating the number of atoms in one amoeba as perhaps 10^17, we find that the expected time to lose even the last atom is remarkably short: less than 60 generations! After that, the odds having one left drop by a factor of a million roughly every 20 generations. I'll let you work the rest of the odds yourself, but be sure that you have space for lots of zeros!

Of course atoms do get recycled, so one could alternatively think about the odds that even one atom of that original amoeba now occupies some place in some current amoeba, albeit in a far different role. That number turns out to be substantially larger and does not diminish much over time. But it's still something like one in a trillion.

So alas, it is almost certain that no physical part of that first amoeba is left crawling around. Only the pattern remains. But isn't it cool that that happens? :D

--Rik

Ecki
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Post by Ecki »

In many older books the floating form of the amoebae is shown as a distinct species, Amoeba radiosa or Astramoeba radiosa. As Ferry pointed out, today it is known that many amoebae can adopt this form.

"Radiosa" is translated "star".

Regards
Ecki

Mitch640
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Post by Mitch640 »

Great information Ecki. I can see where unless you were able to watch him for hours, you might never know he could change to what looks like another species. And usually, the water on a slide evaporates long before you could see the change.

Ferry
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Post by Ferry »

There is a simple way to avoid your slide dries up: put it in a so called moist chamber, a plastic box with a little water on the bottom and something to put your slides on. In this way you can keep your amoeba alive for weeks. They will settle down and can easily be studied. Another advantage is that amoeba which were hidden in the debris before come out. It is the best way to study amoeba, without making cultures.

Success!

Ferry

Mitch640
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Post by Mitch640 »

Ferry, that's a great idea. I bet I can find a Tupperware type seal-able box somewhere. Lining the bottom with a sponge to fit and adding water to the sponge would keep the humidity up and keep the slide off the bottom and out of the water. :)

>Update< I found a Pyrex rectangular shallow dish with a snap on tight fitting plastic lid at Walmart for about $3.50. On the way out, I bought a cheap sponge that I could trim with scissors. I now have the sponge in there, enough water to come half way up the sponge, and wet slide sitting on the sponge, to see how long it will keep water under the coverslip. :)

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