What does a green amoeba eat?

Charles Krebs · Post by **Charles Krebs** » Fri Oct 06, 2006 1:32 pm

Well the ones I have in my current sample really seem to enjoy spirogyra chloroplasts. I've observed about 5 or 6 different occurances of these amoeba up against a spirogyra cell with pseudopodia extended into the cell. In a relatively short time (for an amoeba

) the cell contents were pulled into the test. I found this fascinating and it raises all sort of questions in my mind... need to research this a bit.

The top shot shows one instance of this event.

The second image is a tight shot of one of these amoeba on the move. You can clearly see what I have called "zoochlorella" (I hope thats the correct term) inside the amoeba cell.

The last shot is a nice look at the test itself. The green color is the result of the numerous algae cells in the amoeba.

Wim van Egmond · Post by **Wim van Egmond** » Sat Oct 07, 2006 2:05 am

Great! That first image is almost like someone emptying a glass.

Wim

Ken Ramos · Post by **Ken Ramos** » Sat Oct 07, 2006 4:41 am

Wim commented:

That first image is almost like someone emptying a glass.

Quite right Wim...an amoeba at "happy hour." Cocktails anyone? Great image(s) as usual Charlie.

bernhardinho · Post by **bernhardinho** » Sat Oct 07, 2006 6:49 am

Hi Charles,

great images!! Well, we had a big discussion recently in our german forum concerning Paramecium bursaria and the biology of it's zoochlorella. As far as I know and read, only algae of the genus Chlorella when living as symbionts in a host are referred to as zoochlorella. They live in special vacuoles called perialgal vacuole the chemistry of which prevents the algae from being digested. Here the chloroplasts seem to be prey only.

Best wishes

Bernhard

Charles Krebs · Post by **Charles Krebs** » Sat Oct 07, 2006 9:31 am

Bernhard... thank you for that information! It will help my search for answers. That is exactly what I meant when I said this raises questions in my mind. It does seem like the spirogyra would be no more than "prey". But to my (uninformed) eye, it sure does look like these amoeba carry many "healthy looking" alga cells around inside them.

If you remember the 100X shot of the one that had been "squashed":
http://www.photomacrography.net/forum/v ... .php?t=609
the alga cells look pretty good. If they are no more than food I wonder how long it takes before there is any obvious sign of deterioration. Also the appearance of the alga in the amoeba is so different from the spirogyra chloroplasts.

.... and how do they make those cool looking tests?
Selecting the perfect size particle and "glueing" it in place like an experienced stone mason!

... these little creatures are quite amazing.

Ken Ramos · Post by **Ken Ramos** » Sat Oct 07, 2006 9:56 am

You know in my few years of fly fishing and studying the biology of trout streams, I ran across a case caddis that does something similar. It uses fine bits of sand or rock to build its home, gluing them in place with its silk. Actually when I think about it, they are quite similar in appearance, well almost.

Wim van Egmond · Post by **Wim van Egmond** » Sun Oct 08, 2006 3:21 am

Interesting info on the symbiotic algae, Bernhard! So they don't ingest them? What is the benefit for the host? Is it a bit like ants and aphids? Does the Paramecium bursaria gets some sort of honeydew from the Chlorella?

I always thought they would grow and digest the algae a bit like a green house. Silly me!

Wim

bernhardinho · Post by **bernhardinho** » Sun Oct 08, 2006 7:17 am

Hi Wim,

as it is a symbioses, both partners should benefit from each other (by definition) As a matter of fact the algae perform photosynthesis and produce the sugar maltose (here's your honeydew) and oxygen which the host absorbs and uses partly (about 57%) for its own metabolism. To keep the amount of algae constant, the dividing rates of both organisms have to be (and in fact,are) well coordinated. The great advantage for P.bursaria is of course, a certain indepence of food supply from the envirenmont and therefore can be found in a wider ecorange in the watercolumn (depths).

I have to correct myself in one point: I just read in another book that certain foramimiferes harbour endosymbiontic Chlamydomonas species and the term "zoochlorella" is being used for these too.

Bernhard

Wim van Egmond · Post by **Wim van Egmond** » Mon Oct 09, 2006 2:31 am

Thanks for that useful information Bernhard!!!

Wim

Charles Krebs · Post by **Charles Krebs** » Mon Oct 09, 2006 10:59 am

Rather than start another subject, I'll add this image and a few more observations to this thread. After this subject was initially posted, I looked at few more wet mounts from this sample. I found numerous instances where these amoeba were working on spirogyra... stopped counting after about a dozen. This image is a typical example.

Olympus 10X, brightfield illumination

One thing that I watched for was an instance where the amoeba was able to breach the cell wall of an apparent healthy spirogyra cell. I never came across this, but frequent observations similar to the above image have me curious if they have that capability.

Wim van Egmond · Post by **Wim van Egmond** » Tue Oct 10, 2006 4:00 am

That's a great pic! And now we'll have to wait patiently until the amoeba has managed to pierce the Siprogyra's cell wall!

Wim

thomasr · Post by **thomasr** » Fri Oct 13, 2006 10:46 am

Charles Krebs wrote:Olympus 10X, brightfield illumination

Hello Charles,

that is one of my favourite images, great composition and colors.
Was the water really that clean or did you remove some speckles by image editing?

Thomas

Charles Krebs · Post by **Charles Krebs** » Fri Oct 13, 2006 7:40 pm

Thomas... I tried the "Olympus background subtraction" program that Bernhard mentioned in a post.
http://www.mic-d.com/curriculum/imagepr ... tools.html

I don't know why I had not seen it before, but it is a very nice tool, especially with brightfield illumination. (Thanks for the tip Bernhard!) I do also remove spots from the background with editing software. This is from a stack of 22 images (using Helicon Focus) and spots are sometimes "multiplied" during the process.

thomasr · Post by **thomasr** » Sun Oct 15, 2006 9:02 am

Hello Charles,

I like that Olympus explained their maths for the background subtraction. I must say that your image has made me to "believe" in brightfield again, after all these fantastic DIC micrographs.

Really, you should make a coffeetable picture book with all your work. I don't think it would be hard to find a publisher.

Thomas

Charles Krebs · Post by **Charles Krebs** » Sun Oct 15, 2006 3:59 pm

Thanks Thomas!

I have found thay my DIC does strange things with amoeba tests that are composed of these small pieces of sand and quartz. Many of the particles are birefringent, and seem to "mess up" the light shear that the DIC effect relies upon. So good old brightfield works better. Actually I rarely use "straight" brightfield, generally opting to offset the condenser diaphram at least a small amount to get oblique brightfield.