The more I observe, the more I think the recovery of the population of Japanese freshwater shrimp is an undeniable fact.
What I have explained so far is the hypothesis that the change in the behavior of guppies is due to the development of biofilms and the proliferation of protozoans.
I further developed my hypothesis and began to think that perhaps our "BioCube" is in a state where the development of biofilms and the proliferation of protozoans are more likely to occur.
I mainly referred to the following paper.
Protozoans in the rhizosphere by Shimano Tomoyuki
https://www.jstage.jst.go.jp/article/rootres1992/11/3/11_3_107/_pdf/-char/ja
I can't help but be impressed by how smoothly the Mini-Earth experiment has progressed so far.
At the start, the walls were covered with moss (biologically, green algae or blue-green algae?) but they have been cleaned up.
The population of Japanese freshwater shrimp, which was thought to have been steadily declining due to predation by aggressive guppies, is now recovering, and the guppies have stopped behaving aggressively and have started pecking at the substrate.
However, here, I noticed that compared to previous Mini-Earths, this 1-ton Mini-Earth "Biocube" has many types of "aquatic plants with roots," including Rotala red, which has expanded into the air, Alternanthera reineckii mini, which has also expanded into the air, and Screwvallisneria, which has taken over nearly half the floor space of the "Biocube."
Of these, only Screwvallisneria has been used in previous Mini-Earths, and even then, it was not filled with as much sand as it is now.
The reason why I decided to focus on roots is because I had always been interested in something written on the legendary website "GOOD AQUA" that (1) in an aquarium with aquatic plants that have strong roots, the concentration of nitrates is less likely to rise.
(2) I had heard that in terrestrial plants, the roots and the microorganisms that attach to them have some mysterious interactions, and I thought that something similar might be true for aquatic plants.
So, I've been doing a bit of research on "roots" recently, and I've found a lot of shocking new facts.
Some of what I'm about to write from here on will be common knowledge for those who are knowledgeable about biology, but unless you're really interested in "roots," there's probably some new information here.
Fact 1: Plants can breathe through their roots.
When I think of plant respiration, the first thing that comes to mind is the stomata we learned about in junior high school, but it seems that plants can breathe through diffusion and osmosis.
Apparently this is not possible in places where the cuticle is developed due to the need to resist desiccation, but this may mean that as the cuticle develops, breathing through diffusion and osmosis is no longer possible, and in exchange, stomata are acquired.
Fact 2: In the case of aquatic plants, oxygen absorbed through the leaves and stems is sent to the roots and leaks out from the roots.
Really?!
This means that in the soil, oxygen is supplied to the area around the roots, creating an environment in which other microorganisms can live!
In fact, in an aquarium, the wall is a cross-section of the soil, so you can see air bubbles forming around the roots of the aquatic plants.
From this point on, it is unclear whether this applies to aquatic plants or not.
Professor Shimano's paper is basically about terrestrial plants, but most of what we call aquatic plants have an evolutionary past as terrestrial plants, so it is likely that many of the same things apply to aquatic plants.
Fact-like 1: Plant roots secrete polysaccharides and grow while peeling off surface cells.
And these polysaccharides have the role of reducing frictional resistance when the roots grow through the soil.
Both the polysaccharides and the peeled off cells become food for bacteria as easily decomposable carbon sources.
Really?!
It's supplying oxygen and even food, so it's basically like raising bacteria!
Fact-like 2 :Protozoa gather around, eating the bacteria.
The bacteria mineralize the organic nitrogen in the surrounding area, but when the protozoa prey on the bacteria, some of the mineralized nitrogen is released and absorbed by the roots. Are you even controlling the protozoa?! Hey, roots. Stop it!
Fact-like 3 :It is known that protozoa prey on bacteria, reducing their population, but also stimulate bacterial activity in some way. The same is true for the nitrification of ammonia. What's that?!
I just can't understand it!
Fact-like 4 :Even taking the above functions into account, it seems that plant roots are "over-growing".
The reason for this is said to be that there are bacteria that produce auxin, a plant growth hormone, and when these bacteria are preyed upon by the protozoa, auxin is released. Anything goes, you guys! I'm going to eat some curry buns and go to bed now!
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