Good morning! I have a reputation for being unnecessarily loud, but today I will be breathing harder than ever. This story may become the most important hypothesis in the future as we carry out the Mini-Earth experiment.
What is allelopathy?
According to Wikipedia, allelopathy is a general term for the effect of a plant releasing substances (= allelochemicals) that suppress the growth of other plants, preventing or attracting animals and microorganisms.
The most famous inhibitory effects are those of Japanese knotweed and asparagus.
They are poisonous and eventually kill themselves or cause crop failure.
On the other hand, the most famous stimulatory effect is that tomatoes and basil grow well when planted together.
Allelopathy itself has been studied for a long time, but it seems that there are still many things that are not understood about it.
In particular, there is still no established theory about the relationship between allelopathy and aquariums, and knowledge about allelopathy has not yet been introduced to the aquarium field.
Allelopathy and the final state
Since the early days of the Mini-Earth experiment, I have observed a phenomenon in which even if a large number of types of aquatic plants are put in, most of them die within the first year or so, and only one or two types remain.
And at some point, this phenomenon was called the terminal phenomenon.
I thought it was strange to use English so much, so in this blog I will call this the "ultimate state" and use the term consistently.
Not only aquatic plants, but eventually the freshwater shrimp and snails will also stop having new generations, so I can't prove from past articles alone what I was referring to when I called them the terminal phenomenon in articles from about 10 years ago, but I was clearly aware that plants would become extinct before shrimp and snails .
So, what I want to say now is this.
(1) Mini-Earth is an enclosed tank, so it is the environment where allelochemicals are most likely to accumulate.
This is only a guess, but the need for aquatic plants to suppress other plants through allelopathy increases when the tank is overcrowded and competition for light, nutrients, and space becomes fierce.
Both of these are more likely to occur in Mini-Earth, and because it is enclosed, allelochemicals are not diluted by runoff.
(2) Allelopathy is highly likely to be the cause of the sudden (although over a period of several months) decline in the number of plant species.
(3) Ultimately, shrimp and snails also became extinct, and it is safe to assume that this was due to the decline of the plants that were supposed to support them in the food chain, but perhaps the allelochemicals were also directly damaging shrimp and snails.
(4) So, I wonder if there is a way to stop the accumulation of allelochemicals in Mini-Earth.
As an additional comment on (1), there is a commercialized shrimp Mini-Earth called Beach World.
They choose plants that grow slowly and have low allelochemicals, and deliberately reduce the number of plant species (maybe to one), which may make it difficult for allelopathy to occur and enable long-term maintenance.
It's amazing what professionals make.
However, I have also been successful in generating successive generations of shrimp.
I have been thinking about (2) and (3) for nearly 10 years, and I feel that the plausibility of these theories has increased from the passive approach of not having any other competing hypotheses.
And the question remains: (4) How to stop the accumulation of allelochemicals?
If all the Mini-Earths we have made so far have a lifespan, and even the strongest species, such as the scallop and the amphipod, eventually went extinct because of the accumulation of allelochemicals, then unless we solve this problem, no matter how big a Mini-Earth we make, we are only extending its lifespan by increasing its size, and it will not become a true "small earth."
In other words, I think we need to add the following as a condition for the success of a "Mini-Earth."
So, let me tell you how I am trying to deal with the problem of allelochemical accumulation in this 1-ton Mini-Earth "Biocube," the biggest challenge of my life.
If allelopathic substances are weapons acquired during the evolution of plants, then it would not be strange if organisms that feed on them have evolved to appear.
Like koalas that have evolved to eat poisonous eucalyptus leaves.
However, we don't know at all which plants release allelochemicals and which organisms have the ability to metabolize them.
In other words, this is a mystery that even researchers don't have an answer for.
So, I thought I would put in as many organisms as possible and create as many different environments as possible in the aquarium.
I hope that as many different things as possible, including microorganisms, will live there and someone will neutralize the allelochemicals.
In a broad sense, that's why I divided it into a river sand zone and a platinum soil zone.
And that's why I didn't make it a bare tank, but also deliberately put in aquatic plants that have strong roots.
I'm looking forward to fungi and bacteria that live symbiotically with the roots.
And that's why I'm happy to have planaria.
Surprisingly, something like the planaria's intestinal bacteria might make a breakthrough.
I'm also looking forward to the filtrating intake of the small snails and corbicula.
There might be a super easy scenario in which the allelochemicals are filtered out by these guys surprisingly easily.
Conversely, a pessimistic scenario could be that none of the creatures currently living in the 1-ton mini-earth "Biocube" have the ability to neutralize allelochemicals.
If that happens, we'll reach the ultimate state as before, the number of plant species will decrease, the plants themselves will decrease, and fish, shrimp, and snails will slowly become extinct.
However, there's also a chance that the pessimistic scenario will turn into a divine development along the way.
To tell the truth, this is the scenario I am most looking forward to.
It would be the ultimate heart-warming development where evolution occurs in the Biocube and some organism suddenly acquires the ability to metabolize allelochemicals.
If this were to happen, it would be fungi or bacteria, which have a fast generational turnover.
Moreover, the more allelochemicals there are in the tank, the higher the chance of this happening, so by the time this miracle occurs, it is highly likely that many of the creatures in the Biocube will already be gasping for breath.
If this miracle were to occur and the allelochemicals that filled the Biocube were suddenly rendered harmless, then in theory I would see the creatures recover from the brink of an ultimate state, something that has never happened before.
However, if evolution were to occur in the Biocube and bacteria were to be born that decompose allelochemicals that do not exist in the outside world, then that would be a dangerous creature that must never be allowed to escape.
The reason this would happen is that allelochemicals and the effects of allelopathy that result from them also exist in the outside world, and it is believed that the outside world maintains a stable ecosystem and biodiversity, including these.
If a new type of bacteria with the ability to decompose allelochemicals escapes from the Biocube and invades, it could upset the delicate balance of nature.
I've heard stories of people collecting a huge variety of poisonous insects like snakes, centipedes, house centipedes, frogs, and other disgusting creatures, raising them in the same container like a jar, and making them kill and eat each other, and then extracting something from the surviving creatures that is called "kodoku."
If the ultimate goal of the Biocube is to create a new species of "kodoku," then what have I bet my life on?
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