kscans

Chapter 206 - Episode 5: Latter Half, Oxygen Concentration Is an Economic Fluctuation

With almost no exceptions, animals acquire energy by burning sugars and fats with oxygen. Just like an engine, they need not only fuel but also oxygen. There is another method called fermentation that does not use oxygen, but it is about twenty times less efficient.

Moreover, unlike a car, each and every cell has its own engine. Multicellular animals must constantly deliver oxygen to those engines that are not in direct contact with an oxygen source like the outside air or water. Unlike fuel, oxygen cannot be stored. Consequently, the relationship between breathing methods and oxygen concentration has been an extremely significant factor in determining the major direction of animal evolution, their body plan.

To use an economic analogy, oxygen concentration is like an interest rate. Companies absorb money from financial institutions by paying the cost of interest, and then use that money for their activities. If interest rates are high, inefficient companies that cannot cover the interest will go bankrupt. In a world with a five percent interest rate, only companies that can earn a profit of more than one hundred and six yen from one hundred yen can survive. But even a company that can make a profit of one hundred and ten yen from one hundred yen will go under if the interest rate rises to eleven percent.

In biology, this is what is called extinction. A mass extinction is equivalent to an entire industry being wiped out.

For example, it is probably hard to imagine what could cause the extinction of small organisms like trilobites, which existed in massive numbers all over the world. But it can be explained if you consider that their respiratory organs could not adapt to a drop in oxygen concentration. If food becomes scarce, they can just reduce their numbers. While this might be difficult for large animals, it is possible for small ones. But if the oxygen concentration decreases, every single individual becomes equally unable to survive.

In fact, the Earth's past has seen major fluctuations in oxygen concentration. And the mass extinctions known as the Big Five, with the exception of the one that wiped out the dinosaurs, all coincide with a drop in oxygen levels. The largest extinction event, the Permian mass extinction, occurred during a process where oxygen concentration plummeted from an all time high of thirty six percent to twelve percent.

Conversely, the very few companies that develop new methods of adaptation will sprout as new industries. The prosperity of the dinosaurs was due to their adaptation to low oxygen by developing efficient respiratory organs called Air Sacs. After an extinction, as oxygen levels recover, newly sprouted innovative species flourish, giving birth to various new enterprises.

In a sense, the evolution of life is a repetition of this cycle. A rise in interest rates, which is a drop in oxygen concentration, occurs periodically, destroying a large number of inefficient companies. Then, a drop in interest rates, a recovery of oxygen concentration, allows the innovative companies that survived to develop and prosper.

The efficiency of respiration, so crucial to life, is also greatly influenced by body size. For example, single celled organisms have no respiratory organs. This is because they are small. If a body is small, the oxygen that naturally enters through diffusion from the cell's surface is sufficient.

Next, living on land is a battle against dryness. Increasing surface area means losing precious water from the body.

Therefore, terrestrial creatures evolved lungs within their bodies to efficiently take in oxygen. The Air Sacs of dinosaurs and birds are prime examples. They use a large portion of their bodies to constantly bring fresh air to their blood through the lungs. Even human lungs use countless alveoli, like bunches of grapes, to expand their surface area.

But insects, with their small bodies, are different. An insect's respiratory system is nothing more than Spiracles, which are holes open to the outside, and tracheae, which are tubes connected to them. They have no mechanism to actively inhale air like lungs do and simply rely on air diffusion. They are also exoskeleton creatures. An exoskeleton creature is essentially a living being with something like wax spread over the surface of its skin.

Because their bodies are small, simply having tubes open to the outside is enough for the oxygen that naturally enters. The ratio of volume to surface area means that the smaller the body, the greater the relative surface area. As an exception, flying insects that consume large amounts of energy have created pseudo lungs inside their bodies, cavities formed by swelling parts of their tracheae, which they contract with their muscles.

Now, the insectoid monster before us is larger than we are. And I can see no wings. There should not be enough oxygen to support a body of this size. That leaves two possibilities. The first is that it supplements its energy by directly using magic. The other is indirect use.

I stare intently at the Magic Insect's body. The yellow patterns on its back were so prominent I did not notice it before, but there it is.

"Maytyl. Look at the side of that monster’s abdomen. There are some small patterns, right. Don’t they look like something?"

I pointed at a pattern resembling a spiral for Maytyl. Between the body segments, there were patterns that flickered on and off. Looking closely, I could see holes there, and the patterns were surrounding them.

"...They look like the fundamental magic characters for Spiral Flame."

And with the faint flickering of those patterns, the surrounding hairs were subtly swaying. Those patterns are probably manipulating gas molecules, just like Spiral Flame. Perhaps they are actively sending air into the Spiracles. In that case...

"I think that’s the monster’s respiratory organ. And it’s probably its weak point."

A Magic Seal, evolved to actively manipulate air and draw it into the body, just like Spiral Flame. I wonder if the similar shape is due to convergent evolution. In any case, those patterns are what give that monster enough oxygen to be active.

"...So?"

"Hit it with a Spiral Flame just as it lights up. Can you do it?"

"I’ll try, but I’ll have to get quite a bit closer."

"Got it."

I turned my back. Limping, Maytyl climbed onto me. It was autumn, yet we were both drenched in sweat.

A scorching, concentrated gas shot out from Maytyl’s Sorcery staff. The searing gas reached the pattern on the Magic Insect’s abdomen at the exact moment it lit up. The Spiral Flame, which seemed like it would be deflected by the body hair and diffuse, was sucked right into the Spiracle the instant the small pattern glowed. The monster writhed in agony. Smoke spewed from the hole that looked like a Spiracle.

"It’s working!"

Maytyl said, clinging to me from my back.

"A, alright. Next, destroy the Spiracle on the opposite side of the same body segment."

"Understood. Crenne."

Following my instructions, Maytyl and Crenne worked together to release a Spiral Flame. The enraged monster began to store up electricity. But the charge stopped just before the segment with the destroyed Spiracle.

The monster twisted its body in pain.

"Next. Destroy a Spiracle on a nearby segment, on the same side as before if possible."

"Why do we need to aim so precisely?"

"Well... Unlike humans, they have them on each segment..."

For a human, you just need to block a single mouth, but an insect’s Spiracles are on each body segment. Instead of delivering oxygen to the cells through the bloodstream, they extend branches directly to the cells to supply oxygen. Of course, the tracheae are connected inside, but if they are burned by the heated gas of a Spiral Flame, there is a chance they will get blocked. Even if not, I could expect the oxygen deprivation to become severe in localized areas.

"Crenne. Now is not the time for questions. We’ll do as Ricardo says. We need to finish up over here quickly."

Maytyl looked over at the others. Dagobard’s group was struggling against three, no, four monsters. Another Horse-Dragon had been lost, leaving them with eight. On top of that, they were being pushed back, their distance from us gradually increasing. In other words, they were being forced towards the lake.

"I’ll go tell them about the strategy."

"But..."

"I could be wrong, but this monster seems to have a strong tendency to decide its targets based on magic. I can probably get close safely."

From my observation, it had paid me almost no attention. If there was even a single dire wolf in the forest, I would be done for, but from the looks of things earlier, it was highly likely they were afraid of the Magic Insect and were staying away.

"...Understood. Take this with you. It is the seal of a royal who has entrusted you with their full authority."

Maytyl pulled off a ring and handed it to me. "Your Highness," Crenne said in a panic, but Maytyl stopped her with a hand and told her to resume the attack. While they did that, I ran straight towards the lake.

Dagobard was bravely fighting the Magic Insect at the very front. But he still could not do more than keep it at bay.

"Prince Dagobard!"

I shouted at the Empire’s prince.

"Ricardo Vinder. What are you doing here. Don't you see the situation?"

"Look at that. I have a plan to strike the monster’s weak point."

I yelled while holding out the ring.

"Those yellow patterns on its side. Hit them with a Spiral Flame the moment they light up. They’re the Magic Insect’s respiratory organs, and they’re its weakness."

"How am I supposed to understand with just that explanation?"

"Here!"

I threw the jar filled with IG-1 that I was holding in my hand at the monster. With a basha sound, the monster’s Spiracle was stained green. At the same time, its flickering ceased. The Magic Insect seemed annoyed and rubbed the inhibited Magic Seal with its leg.

"...Knights of the Kingdom, dismount your Horse-Dragons. Craig, while we provide a diversion, aim for that pattern with Spiral Flame. He says it’s on the complete opposite side."

"Understood."

At Dagobard’s words, Craig-dono and the others dismounted their Horse-Dragons. Dagobard’s group approached the monster I had thrown the IG-1 at.

Dagobard drew the Magic Insect’s attention. Meanwhile, Craig-dono got closer to its side. Craig-dono and his men focused their Spiral Flames. Their accuracy was not quite on par with Maytyl’s group, but one of the Spiral Flames caught a small pattern. The Spiracle spewed smoke. The monster that had been bearing down on Dagobard’s Horse-Dragon troop, about to crush them, began to struggle. The Horse-Dragons slipped through the gaps between its legs.

Behind me, there was a thud. The Magic Insect Maytyl had been fighting had flipped over onto the ground, its legs twitching. With that, the balance tilted in favor of humanity, our side.

With Maytyl’s group joining the attack, the outcome was decided. After Dagobard’s spear gouged out the Magic Seal on the Spiracle of a monster whose current had died down, the last and largest Magic Insect fell.

"We managed somehow, didn’t we."

Maytyl said as she joined us, wiping her cheek. Crenne was supporting her limping superior.

"...We lost two Horse-Dragons."

Dagobard said. Fortunately, the knights riding them were apparently unharmed, but the knights who had received an electric shock through the Horse-Dragons were still unable to stand. One could not say it was only two. Horse-Dragons are precious. It could mean that a village in the Empire that could have been saved will now perish. Dagobard’s gaze fell upon me, and I stiffened involuntarily. This exploration was my proposal.

I believed it was necessary, but if I were to be accused of underestimating an unknown danger after seeing the purple magic, I could not argue.

"I trust this will yield results worthy of the cost."

The fact that he had no intention of blaming me emotionally was, conversely, a heavy pressure. I looked straight at Dagobard and nodded.

"For that, please give me just a little more time."

I explained about the Glacial Varved Clay. In truth, we should probably leave this place as soon as possible. But Dagobard decided to continue. In the meantime, Maytyl proceeded with collecting samples.

"As expected of a place next to the Blood Mountains, they have some incredible creatures here."

"It’s the Mountains of Despair. Now that we know how to defeat them, they’re no longer a threat, but still..."

Craig-dono and Dagobard were talking in front of the monster’s carcass.

"As usual, Ricardo, who figured out the monster’s weakness, is up to something."

"Hmph. What is he planning?"

I casually tried to avoid the two of them and approached the monster. Of course, I was spotted.

"No, I was just checking something..."

As I said that, I looked at the tips of its slender legs. They were single-pronged. Covered in short body hair, they did not look like they could carve stone. Next, I moved to its back. I peered into the gaps between the segments that corresponded to its thorax. ...There was not even a trace.

But it still bothered me. This thing looks like something.

"Just in case, can we take one of the smallest ones back with us?"

I pointed to the smallest individual, one about the size of a Horse-Dragon.

"Give me a reason."

"At this stage, I can only say it bothers me. But if this monster, no, this Magic Insect was drawn to the purple light, it might be related to the calamity."

"...We’ll carry it as far as Mardras. We might be able to obtain new materials from it."

Dagobard prodded the exoskeleton covering the Magic Insect's body with his spear. In short, he would grant my request, but ownership would belong to the Empire.

"That is more than enough."

I nodded.