Vacuoles, Form and Cannibalism?

A collection of miscellaneous images

By Paul James, UK

Clearly it seems that one of the very first hurdles encountered by the emerging unicellular life forms was the problem of dumping excess water that seeped into the cell by the osmotic process. The established method : that of collecting this unwanted water into an expanding 'vacuole' ready for pumping back out evolved to deal with this rapid hydration. The novice soon learns to spot the presence of these ubiquitous cavities quite quickly throughout the huge range of protists that soil/pond water hosts.

Sometimes it is not easy to distinguish between water and food vacuoles, but all unicellular life forms must have to rid themselves of excess water, so if only one vacuole is present at the moment of observation it is likely to be one dealing with the osmotic problem. Food vacuoles are not always present of course, and the various species of amoeba deal with food particles in slightly different ways. Often we see particles of food tumbling inside beside the rest of the cell contents without any apparent self-containment inside a vacuole. Some varieties have more than one water vacuole which often fuse together into a very large cavity before expelling the water through the ectoplasm, whilst others appear to constantly possess several simultaneously.

I thought of posting a few images of amoeba gleaned over the years which illustrate the variation water vacuoles take in size, position and number. The soil/pond water enthusiast soon learns that there are many amoeboid varieties throughout the species, ( literally thousands ) a few of which become familiar to the eye over the years. My own home patch sports various forms which I give simple personalised names such as the 'Carpet Slipper' ...... ' Balloon'......'Skull'......' Formula 1' etc. as I recognise them during observation !

Water or food vacuole ?.......... it's large for a tiny amoeba

Two water vacuoles fusing into one. Note the nucleus pinched between

the ectoplasm and vacuole.

Almost perfect clock dial formed symmetry from resting amoeba which nevertheless

has to continue pumping out water regardless.

Curious form showing 'tail' water vacuole imitating the

neck of a balloon.

Three large vacuoles in an unusually rectangular cell form I've not seen before.
Difficult to distinguish between water and food vacuoles from a single

image like this. Prolonged observation will provide the answer but can

take longer than expected for the water to eject in some examples.

At around the time of collecting together the images for this article during a session of observation, I chanced up a rather curious sight of an a soil amoeba which seemed to have engulfed another, albeit a lot smaller. The best image of this from a large sequence recorded onto my digicam's memory card is shown above, which incidentally has been contrast enhanced to make the illustration of the endoplasm a little clearer. On the right is an example of a tiny soil amoeba at about the same amplification as the main image. Though there is no doubt that there is a similarity between the two, I cannot be certain that this is an example of 'cannabalism', but the ingested amoeboid form appears to be genuine. I wonder how many other observers have noticed a similar feeding habit ?

If my images appear a little soft it is simply because I have left them so and importantly removed all noise from them, then compressed the files into small sub 10k packets. As a frustrated dial up subscriber I have to consider my own uploading times, and no doubt too hopefully at least, someone somewhere with similarly poor web access might be glad of an article that's easily down loaded.


All comments welcome by the author Paul James


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