Lives within lives

Life on this world takes many forms, and science sometimes discovers aspects of biology which are as strange and fascinating as anything one might expect to encounter on an alien planet.  Consider the case of Mixotricha paradoxa.

Mixotricha is a protozoan -- a microscopic one-celled organism (there are many species of protozoa, amoebas being another example).  Under the microscope, it appears vaguely pear-shaped, covered with roughly a quarter million "cilia" -- tiny hair-like growths which wave in a synchronized way to propel it through its environment.  (That environment itself is of some interest, but I'll be getting to that in a moment).  Many protozoa have cilia, but Mixotricha is different.  Its cilia are not really cilia.  They are separate organisms, bacteria of the "spirochete" type, long and thin and active.  These spirochete bacteria are attached to the surface of the Mixotricha by brackets and are symbiotic with it.  They have been compared to rowers propelling a ship.

You might be surprised that so many bacteria could be attached to one protozoan; however, even though bacteria and protozoa are both microscopic one-celled organisms, there is a tremendous difference in size between them.

There exist on Earth two distinct types of cells.  The "prokaryotic" type is tiny and simple, with very little internal structure; the "eukaryotic" type is far larger, with complex internal structure including a distinct nucleus.  Bacteria, and a class of similar organisms called "archaea", are prokaryotic cells.  All protozoa are eukaryotic cells.  All multi-cellular living things -- animals (including humans), plants, fungi, etc. -- are made of eukaryotic cells.

Aside from the spirochetes, three other species of bacteria are symbiotic with Mixotricha, living on or even inside it, performing a variety of functions without which it could not survive, such as extracting energy from the nutrients which it absorbs from its environment.

(It's now believed, by the way, that eukaryotic cells first arose as symbiotic combinations of the original, simpler prokaryotic cells.  Modern animal cells contain small fuel-processing bodies called mitochondria, which have their own DNA and whose "ancestors" must have been bacteria which became symbiotic with larger cells billions of years ago and ended up being absorbed by them.  The same is true of the chloroplasts (photosynthesizing bodies) within plant cells.  Modern Mixotricha's symbiotic relationships may resemble the arrangements which gave rise to eukaryotic cells in the first place.)

Mixotricha are not solitary creatures; they swarm through their environment in substantial numbers.  And each individual one of them is, as we have seen, host to a whole community of hundreds of thousands of bacteria.

And what is that environment in which these Mixotricha live and move?  It is the digestive tract of a termite -- specifically, a termite of a species native to northern Australia.  You probably know that termites cannot, on their own, digest the wood they eat; they are dependent on micro-organisms inside their digestive systems to do it for them.  Mixotricha is one such micro-organism.  (Different species of termites use different species of microscopic helpers.)

Termites, of course, are social insects, living in colonies which, for some species, can number in the millions.  Most of the termites in a colony are sterile, with a few "queen" termites functioning as egg-laying machines.  Rather than viewing each termite as an individual, it's probably more correct to think of an entire colony as a super-organism, with the "queens" being analogous to stem cells which replenish the colony's numbers to replace worker termites as they die off; and the flying termites which sometimes leave to start new colonies are the super-organism's reproductive organs, or spores.

So that super-organism consists of a swarm of individual termites, each of which contains countless Mixotricha in its gut, each of which in turn is host to its hundreds of thousands of symbiotic bacteria.

Lives within lives within lives within lives.....

Videos of the day -- Ruth Aisling

On my post about travel last week, a couple of people expressed an interest in Scotland.  As it happens, one of the YouTubers I most frequently watch is Ruth Aisling (pronounced ASH-ling), who specializes in travel around Scotland and makes spectacular videos showcasing the country.  She has some experience with travel, having lived in Mexico and Japan (and can speak Spanish and Japanese), but eventually returned to her own country for some in-depth exploration.  She's been traveling around Scotland by herself for three years and has covered some very remote places as well as major ones.  She uses a camera drone, which explains the numerous aerial views (and how she can include herself in moving shots from a distance without a camera crew).

Her videos are on the longer side, generally twenty to thirty minutes -- much longer than I will generally watch, but I always find them so absorbing that I almost end up wishing they were longer.

This one is about Stirling, the "smallest city in Scotland" at thirty-five thousand people ("city" in the UK has an exact legal definition which isn't entirely based on size).  While small enough to get around easily, it's crammed with interesting relics of centuries past.  The visit to Stirling Castle starts at 14:50, but the whole thing is well worth watching if you're interested in the country -- use fullscreen of course.


An example of a remote place, which tourists usually overlook, is the small island of Gigha on the west coast.  With fewer than two hundred inhabitants, the island used to be the property of a big landowner, but was bought by its people in 2002 and is now community-owned.


Aisling's video channel is here, and she has a general website here.

Truths and inspirations for 25 May 2026

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[For the link round-up, click here.]

Evidently my assessment of this song was correct.

I'll be surprised if I get even that.

Keep resisting.  Stand up for the innocent.

We need both, and it's a plain fact that vaccines revolutionized human survival in the face of disease.  But prevention, especially healthy eating, is seriously neglected in the US -- and note that it's mostly the same kind of people who are anti-vaccine who are also belligerently assertive about eating the flesh of filthy animals and processed junk full of fat and/or refined sugar.

Yes, it is actually possible to be this stupid.