The evolution of insect swarms from XNUMX million years ago

Chapter 75 The idea of ​​​​landing

Landing on land, for early aquatic organisms, is no less a feat than humans flying into space, but for arthropods, it is inherently simpler.

For animals, leaving the water source and landing on land, the most critical aspects are nothing more than maintaining moisture, breathing air, resisting ultraviolet rays, and supporting the body.

For arthropods, many of these are not a problem.

The first is to stay hydrated. Although it has various shortcomings, it is undeniable that the exoskeleton structure, in addition to the armor, is also inherently capable of locking water in the body to prevent loss.

At the same time, the exoskeleton can also effectively block ultraviolet rays and protect the fragile cell tissue underneath. In this way, two problems are solved at once.

It is precisely for this reason that different groups of living arthropods parted ways in the ocean and landed independently.

Chelicora, the ancestors of later generations of spiders and scorpions, is still unknown among the bottom-dwelling horseshoe crabs picking up trash.

Myriapodia, the ancestor of the centipede millipede in later generations, is speculated based on its morphology. It is most likely that it is currently picking up garbage in the intertidal zone of the coast together with the shrimp.

The Crustacea, the ancestors of later generations of shrimps and crabs, have evolved into bivalve arthropods such as leaf shrimps and baghead shrimps. However, except for the baghead shrimps, which are more competitive, they have chosen to directly kill other garbage-picking creatures. Most of them They also pick up garbage on the seabed in special environments such as the Dikla Crater.

Only Hexapod, the ancestor of later generations of insects, is currently a mystery. However, with the hardware level of these guys at this time, 80% of them don’t know where to put them to pick up garbage.
  Later studies showed that all groups other than Crustacea landed in the Silurian Period and began to flourish in the Devonian and Carboniferous Periods.

The reason why the differences between the major groups are mentioned is to lead to the next question - how to obtain oxygen from the air.

Terrestrial arthropods adopt a valve-type respiratory system, but within the respiratory system, they have a completely different respiratory structure.

The chelicerate subphylum improved the gill structure for breathing in water. In fact, it was simply wrapped into the body to form book lungs - envy, the legs were replaced.
  At the same time, they have copper-containing blue blood that participates in transporting oxygen. The respiratory systems of the other two types of terrestrial arthropods are much simpler. Blood or body fluids do not directly participate in oxygen transportation, but are absorbed directly through the structures on the body wall.

At this point, the new grade finally had a problem that Lin Yi needed to use gene editing to solve.

Since there is already a book gill structure, Lin Yi naturally chooses a more efficient solution to wrap the book gills into the body to form book lungs.

For the relevant gene sequence, Lin Yi had combined the book gills with the water jet propulsion system when he was developing the mother lobe, so it was not difficult to wrap it in the body.

The lung structure of the book lung gradually took shape. At the same time, Lin Yi also arranged for it an active breathing organ derived from the corner stone water jet propulsion system, allowing it to continuously and actively take in air.

An entire structure that can absorb oxygen from the air is completed. As for the problem of missing legs, there are genetic modification methods to cover it up, and Lin Yi can create as many pairs of appendages as he wants.

Now, he has a way to solve the problem without returning the book gills to his ancestors. The relevant gene sequence comes from the previously captured large-appendage genus Helocarpus - Segment Development.

During the growth process of these arthropods, body segments increase with age, which is known as molting. By integrating and modifying these related gene sequences, the body segments of an individual can be increased and more appendages can be grown out of thin air.

The appearance of the new template refers to Gonghao, which is the short-winged horseshoe crab template. Because the main purpose is exploration rather than combat, and there are no other levels on land to provide supplies, the stepping structure and feeding structure designed by Lin Yi for the new level are relatively conservative.

It does not have the ferocious sickle limbs that are highly specialized like those of the soldier. It is still a classic combination of five pairs of appendages and two pairs of chelicerae. It is mediocre but has strong versatility and can take care of eating, hunting and other functions at the same time. need.

When it comes to appendages, it brings up the last problem, which is the problem of continuing to support the body without the buoyancy of water.

Losing the buoyancy of water and supporting the body will become one of the three most important problems plaguing the body shape of arthropods, along with oxygen and nerves.

Even in the era when Lin Yi lived in later generations, the extreme size of marine shrimps and crabs far exceeded that of any terrestrial arthropods of the same period. The largest arthropod ever recorded, the horseshoe crab Rhinejecker, was also an aquatic species.

Therefore, in order for the new class to move normally on land, the first thing that needs to be modified is the thickness of the appendages and the amount of internal muscles.

However, this problem is no longer a problem for Lin Yi now. He directly reduced the double-shell pseudo-endoskeleton structure of the Dreadnaught Soldier and the second-generation Pioneer Mother and installed it on the new grade's body, making the new grade's five pairs of weight-bearing legs particularly strong.

In addition to the overall thickness issue, the structure of the appendage end is also a key factor affecting the creature's ability to move on land.

At this point, arthropods are somewhat inferior to the lobe-finned fish that landed later.

The fleshy fins of fish are spread flat to have enough contact area, and the legs of early arthropods are mostly similar to the legs of later shrimps and crabs, with long and pointed ends, suitable for walking on the sandy ground on the seabed, but on land, it is easy to He sank into the sand and found it difficult to support his body.

Even the orthoshrimps and even the myriapods of later generations were not further optimized at this point, leaving only the crawling trace fossils in the sandstone layers.

The improvement method is also very simple. Transform the last section of the appendage into a wider and flatter shape, and lay it flat in a splayed shape to form a structure called a tarsus.

Later generations of insects also further improved the tarsal structure and evolved two chitinous tarsal claws for better gripping various surfaces. But now Lin Yi doesn't need to fix this, he just needs to increase the gripping area of ​​the hocks.

The five pairs of weight-bearing feet were quickly transformed, and the gene sequence related to the chelicerae did not need to be edited in detail. It was enough to slightly increase its muscle strength so that it could swing normally on land.

At the same time, the sword-like telson from the Brachyphylla template was also retained.

Although theoretically no terrestrial predators in this era need the short-winged horseshoe crab's tail spines for defense, Lin Yi still installed this shorter tail segment to maintain the balance of its body.

In this way, a new level called Exploration Engineer was born. In the plan, they will move forward along the river that flows into the sea area of ​​​​Dikla Crater to see if the inland of this era, at least on both sides of the river, can bring him any surprises.

(End of this chapter)