Amoeba attack sequence

[ddy5]

Several times I've seen amoeba change course, apparently to go to a potential meal. Are amoeba able to detect prey/food without actually coming in contact with it? Here is an example:

I was photographing the pretty gold amoeba (a flamellid?) when a large (100-200 µm), dark, spindly amoeba appeared some distance away. (The white, spikey blob is a hypotrich ciliate out of focus.)

Amoeba attack A copy.jpg (116.48 KiB) Viewed 1426 times

The intruder was moving past, but then made a right-angle turn and went toward the flamellid.

Amoeba attack B copy.jpg (98.99 KiB) Viewed 1426 times

Amoeba attack C copy.jpg (103.74 KiB) Viewed 1426 times

The intruder then ripped its prey apart and devoured it. Brutal.

Amoeba attack D copy.jpg (101.69 KiB) Viewed 1426 times

This all happened quite quickly, at least in amoeba-time: the killing commenced less than a minute after the intruder appeared. The black blobs in the photo are rough body outlines of the attacker.

Attack timing.jpg (246.01 KiB) Viewed 1426 times

The intruder did appear to 'sense' a meal nearby, and respond by changing course. It's not definitive, however. Both species had very long pseudopodia, and it's possible that they touched somewhere out of the plane of focus. Has anyone else seen comparable behavior and/or know what's going on?

Cheers, David

[Wes]

Hi David,

Thank you for this superb sequence. Fascinating subject and excellent quality! Looking forward to more

[Dennis]

ddy5,
So.....
An Amoeba ate another Amoeba.

Good stuff !!!

-Dennis

[Javier]

Such a cool register! Congratulations.

I have also seen amoebas to change direction to chase food.

[imkap]

Thanks for this. Excellent photos, I can't help but to ask about your setup. Please share, thanks

[Dubious]

An excellent forensic record!

I don't know exactly what first alerted the amoeba here, but amoebas are able to sense and follow chemical gradients in the water to get to prey.

https://onlyzoology.com/how-does-amoeba ... ar-stimuli

[xioz]

I would guess most microbes are able to detect chemical gradients, I read somewhere that this is very basal to most organisms. Basically what the sense of smell and taste developed from.

Anyone know more?

[ddy5]

Thank you all for your comments. They stimulated me to do some more digging on the question of chemical signals and signal detection. Most of the research is on Dictyostelium (slime mold), a 'social' amoeba that uses chemical signals extensively. That's a special case, however. A few papers dealt with medically important amoeba (live in brain, gums, and gut) that also probably use chemical signal detection. I did find one study on a normal, aquatic amoeba that does not use chemical detection for hunting. Bottom line: chemical detection is important for hunting and general navigation in amoeba, but may not be universally used, i.e., more research is needed.

The setup for taking the photos was nothing exotic: Nikon microscope and camera, normal DIC, and a high-speed flash (hardly necessary for amoeba photography). Editing and creating the overlays in Photoshop.

Cheers, David

[blekenbleu]

Bacteriophage viruses seemingly detect changing levels of CtrA protein in host bacteria.
https://www.frontiersin.org/articles/10 ... 18015/full

[xioz]

Thank you all for your comments. They stimulated me to do some more digging on the question of chemical signals and signal detection. Most of the research is on Dictyostelium (slime mold), a 'social' amoeba that uses chemical signals extensively. That's a special case, however. A few papers dealt with medically important amoeba (live in brain, gums, and gut) that also probably use chemical signal detection. I did find one study on a normal, aquatic amoeba that does not use chemical detection for hunting. Bottom line: chemical detection is important for hunting and general navigation in amoeba, but may not be universally used, i.e., more research is needed.

Great that you did the digging even if the answer is as if often the case "more research needed"! Interesting to know there are exceptions but that raises the question if chemical signals aren't used for hunting, what do they use? Vibration is the only other thing I can think of.