Exploring the Enormous Organisms of the Carboniferous Period

[Eagle9]

Hello

I have heard that various organisms in Carboniferous period had gigantic sizes because of relatively high Oxygen level in atmosphere. Today it is equal to 21 %, but at that time it was higher:

The growth of these forests removed huge amounts of carbon dioxide from the atmosphere, leading to a surplus of oxygen. Atmospheric oxygen levels peaked around 35 percent, compared with 21 percent today. It also may explain the giant creepy-crawlies that now emerged—the size reached by insects and similar creatures is thought to be limited by the amount of air they are able to breathe.
Deadly poisonous centipedes some six feet (two meters) in length crawled in the company of mammoth cockroaches and scorpions as much as three feet (one meter) long. Most impressive of all were dragonflies that grew to the size of seagulls. One exquisitely detailed fossil of a dragonfly that died 320 million years ago shows it had a wingspan of 2.5 feet (0.75 meters).

https://www.nationalgeographic.com/science/article/carboniferous

So, organisms were very big, but I do not really understand why. What is the biochemical grounding for linkage between Oxygen’s level in atmosphere and organisms’ size? Is there really a direct correlation? Can one make such experiment - creating orangery where Oxygen’s level will be 35 % and then let’s see if plants (ferns for example), insects and other organisms become larger. Of course, many years are needed for plants to grow up, but insects grow much faster. It will be very interesting to see human-size fly or bee in such simulated experiment. Has anybody done this? Will it be very expensive? Or can we apply to genetic engineering to make current insects so large again?

 

[BillTre]

It would be easy to do the experiment you propose; raise some fruit flies in an increased oxygen atmosphere.
It takes about a week or two for a Drosophila egg to grow to an adult.

I don't know that that has been tried, but if it worked it probably would have been in the science news.

I would not expect it to work because there was probably some genetic involvement in size the insects would be able to achieve. It's obtainable size would be part of their adapting to their environment.
Raising flies in an increased oxygen environment for a long enough time for them to evolve increased size would be more difficult because many generations would have to be held in that atmosphere for many generations (probably many, many). You might be able to speed it up by mutating the flies at some level, to increase genetic variability, but it seems unlikely (to me) that you would see any effect very quickly.

 

[Bandersnatch]

So, organisms were very big, but I do not really understand why.

The carboniferous gigantism concerns mainly arthropods (not all organisms; while fern sizes are unrelated to oxygen concentration, but rather due to simple filling of evolutionary niches).
These animals got so large through evolutionary selection over many generations - not by individual exposure to higher levels of oxygen.
And it helped those animals specifically, because they have inefficient respiratory and circulatory systems. When you don't have no fancy lungs, nor veins, to carry the oxygen around your body, and instead have to rely on mostly passive diffusion, you can't grow your body too large. Else the deepest tissues will suffocate.

 

[pinball1970]

Hello

I have heard that various organisms in Carboniferous period had gigantic sizes because of relatively high Oxygen level in atmosphere. Today it is equal to 21 %, but at that time it was higher:
https://www.nationalgeographic.com/science/article/carboniferous

So, organisms were very big, but I do not really understand why. What is the biochemical grounding for linkage between Oxygen’s level in atmosphere and organisms’ size? Is there really a direct correlation? Can one make such experiment - creating orangery where Oxygen’s level will be 35 % and then let’s see if plants (ferns for example), insects and other organisms become larger. Of course, many years are needed for plants to grow up, but insects grow much faster. It will be very interesting to see human-size fly or bee in such simulated experiment. Has anybody done this? Will it be very expensive? Or can we apply to genetic engineering to make current insects so large again?

In terms of why these animals were able to get so large, the oxygen levels would enable effective ATP metabolism.
ATP provides energy to build and getting large would confer an evolutionary advantage for competing for food and mates.

 

[BillTre]

When you don't have no fancy lungs, nor veins, to carry the oxygen around your body, and instead have to rely on mostly passive diffusion, you can't grow your body too large.

Their respiratory system is considered less efficient, but it is a tracheal system to distribute air (for oxygen going in and CO₂ going out). Body movements (during exercise, when gas exchange demands would be greater) help pump air in and out of the blind ended tracheal tubes. The trachea branch throughout the insect's body.
More turnover of tracheal air would increase the concentration differences across the membranes separating the body fluids and inhaled air. The concentration differences would drive the gas exchange. The upper limit of concentration differences ,would be limited by the (oxygen) concentrations in the atmosphere.

The insect circulatory system, which could move internal fluids, to distribute dissolved gasses to some extent. around, is an open system where the eart pumps blood out to the tissues. However, the flow back from the tissues is through tissue spaces and sinus-like spaces (probably also enhanced by body movements).

 

[jim mcnamara]

The simple answer has been given a couple of ways. Arthropods - insects, scorpions, centipedes - have holes in the side of the thorax. Spiracles. They provide oxygen by diffusion only. Passive, no diaphragm. What counts is the oxygen concentration (partial pressure of oxygen) in the atmosphere.

The flip side of this is there have been times of lower levels. The range is 15% to 30% per the link below.
See $O_2$ levels during the Phanerozoic (550 mya to today):
https://www.pnas.org/content/96/20/10955

It explains why.

Also, humans have high elevation (lower total oxygen) genetic adaptations for dealing with hypoxia:
http://genesdev.cshlp.org/content/28/20/2189.full

 

[Eagle9]

Raising flies in an increased oxygen environment for a long enough time for them to evolve increased size would be more difficult because many generations would have to be held in that atmosphere for many generations (probably many, many). You might be able to speed it up by mutating the flies at some level, to increase genetic variability, but it seems unlikely (to me) that you would see any effect very quickly.

But if genetic alterations are not absolutely necessary, then during several years (and hence about 100 generations?) we can probably achieve desired goal?

The carboniferous gigantism concerns mainly arthropods (not all organisms; while fern sizes are unrelated to oxygen concentration, but rather due to simple filling of evolutionary niches).

So, can they in principle grow 30-40 m height? If only “niches” matter, then why nobody tried to receive such giant ferns? It would be very attractive achievement

And it helped those animals specifically, because they have inefficient respiratory and circulatory systems. When you don't have no fancy lungs, nor veins, to carry the oxygen around your body, and instead have to rely on mostly passive diffusion, you can't grow your body too large. Else the deepest tissues will suffocate.

Their respiratory system is considered less efficient, but it is a tracheal system to distribute air (for oxygen going in and CO2 going out). Body movements (during exercise, when gas exchange demands would be greater) help pump air in and out of the blind ended tracheal tubes. The trachea branch throughout the insect's body.

More turnover of tracheal air would increase the concentration differences across the membranes separating the body fluids and inhaled air. The concentration differences would drive the gas exchange. The upper limit of concentration differences ,would be limited by the (oxygen) concentrations in the atmosphere.

The insect circulatory system, which could move internal fluids, to distribute dissolved gasses to some extent. around, is an open system where the eart pumps blood out to the tissues. However, the flow back from the tissues is through tissue spaces and sinus-like spaces (probably also enhanced by body movements).

The simple answer has been given a couple of ways. Arthropods - insects, scorpions, centipedes - have holes in the side of the thorax. Spiracles. They provide oxygen by diffusion only. Passive, no diaphragm. What counts is the oxygen concentration (partial pressure of oxygen) in the atmosphere.

So to conclude, primitive internal organs and systems enabled those organisms to reach big sizes, is it correct?

In terms of why these animals were able to get so large, the oxygen levels would enable effective ATP metabolism.ATP provides energy to build and getting large would confer an evolutionary advantage for competing for food and mates.

So, no genetic changes/engineering is needed in order to receive such giant species?

The flip side of this is there have been times of lower levels. The range is 15% to 30% per the link below.
See O2 levels during the Phanerozoic (550 mya to today):

Perhaps, but I am speaking about Carboniferous period of Paleozoic Era I love this period since my childhood

 

[BillTre]

But if genetic alterations are not absolutely necessary, then during several years (and hence about 100 generations?) we can probably achieve desired goal?

If genetic alterations (meaning evolutionary changes) were not necessary, then I would expect changes like these to happen in one to a few generations.
One generation would be the simplest case, all depends only on oxygen concentration.
Possibly, a few generations if there were some "meta-genomic" changes involved.

A hundred generations might be the result of some selection on the genome (but you would need a source of genetic variation which could be selected).

 

[Eagle9]

If genetic alterations (meaning evolutionary changes) were not necessary, then I would expect changes like these to happen in one to a few generations.

One generation would be the simplest case, all depends only on oxygen concentration.

Possibly, a few generations if there were some "meta-genomic" changes involved.

Sound easy to do, why nobody tried to do it?

 

[Tom.G]

Sound easy to do, why nobody tried to do it?

Perhaps for the same reason you haven't done it; doesn't seem to be worth the effort for the possible returns.

 

[256bits]

I have heard that various organisms in Carboniferous period had gigantic sizes because of relatively high Oxygen level in atmosphere.

But the reference you quoted states,
Atmospheric oxygen levels peaked around 35 percent, compared with 21 percent today. It also may explain the giant creepy-crawlies that now emerged.
With an emphasis on the word 'may;.

A higher oxygen level should provide a potential for a larger organism to exist, but it would not be the only deciding factor.

 

[Eagle9]

Perhaps for the same reason you haven't done it; doesn't seem to be worth the effort for the possible returns.

But it seems to be quite easy and interesting (I mean results)

But the reference you quoted states,

Atmospheric oxygen levels peaked around 35 percent, compared with 21 percent today. It also may explain the giant creepy-crawlies that now emerged.

With an emphasis on the word 'may;.

A higher oxygen level should provide a potential for a larger organism to exist, but it would not be the only deciding factor.

Perhaps
But if I had free money I would make such experiments regardless it will yield some practical resulst in biology or not, it is just curiosity