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"Bring science home" all
Written by Seven Kings
Originally, the "18th generation of ancestors" had no meat and no joy, but in less than 40 years, they began to turn to vegetarianism, and even grew a new body structure in order to be vegetarian. Today we will talk about a creature that can quickly evolve and adapt to the environment - the Italian wall lizard.
Italian wall lizard (Podarcis siculus). Image source: wikimedia
The Italian wall lizard (Podarcis siculus) is a tiny reptile with a body length of less than 13 centimeters. Their home is in the Mediterranean region of Europe, where they are carnivores and love to eat a variety of arthropods, such as insects. Because they are cute and cute and in such numbers, they are not only treated as pets, but also as important experimental subjects for researchers.
But who could have predicted that this seemingly blinking little thing would dare to align itself with Darwin's classical theory of evolution, grow a new body structure out of nothing in a short period of time, and embark on an evolutionary path similar to fat da.
It all started in 1971. That year, Duncan Irschick, a biologist at the University of Massachusetts, and his colleagues came to Croatia to work on a project. They caught five pairs of Italian wall lizards on the island of Pod Kopiste in the southern Adriatic Sea and brought them to the nearby island of Pod Mrcaru.
Five pairs of Italian wall lizards from the island of Pod Kopiste (left) near Croatia were brought to Pod Mrcaru and began to evolve to vegetarianism. Image source: prayoga.org
However, an accident occurred.
The Croatian War of Independence broke out. The war was fought for about 20 years, and it wasn't until the mid-1990s that it was completely over. Due to the war, the researchers had to interrupt their research and leave the lizards on the island.
This accident of human society has brought about the accident of evolution.
In 2004, Croatia resumed tourism on The Island of Bode-Makalu, and researchers were able to return the original experiments. At first, the researchers weren't sure if the lizards were doing well, or even if they were alive. But they were taken aback by the sight of the island.
Irschick recalls, "The island was full of lizards. "This was not a big deal, because Pod Makalu island has its own lizard breed: the Podarcis melisellensis. However, genetic analysis of the Bode-Makalu lizards showed that none of these lizards were Dalmahitian wall lizards, but all were descendants of the original 5 pairs of Italian wall lizards.
The researchers also found another amazing thing: The more than 5,000 offspring of these carnivorous lizards are now all vegetarian. Keep in mind that on Pod Kopiste, the home of these lizards, vegetarian food accounts for only a negligible part (less than 7%). But the Italian wall lizards on the island of Bode-Makaru are not only vegetarian, but also very well fed: vegetarian food accounts for 34% of their rations in the spring and becomes a staple food in the summer, reaching 61%.
Image source: pxhere
In the eyes of most biologists, it is inconceivable that meat-eating animals are suddenly able to eat vegetarian and digest ultra-difficult cellulose and lignin, because only a very few microorganisms on Earth (such as white rot bacteria) can break down these complex organic polymers.
During the Carboniferous Period (about 300 million years ago), it was because there was no biological energy to decompose plants that the remains of plants that could not be decomposed slowly turned into coal underground. Now the animals on the earth can not directly digest plant fiber, cattle, horses and other herbivores need to use microbial fermentation, so it is necessary to grow a huge digestive tract that acts as a fermentation tank.
Coal is actually the "green pollution" of the Carboniferous Earth. Image source: rawpixel
Because of this, many researchers have believed that in order to eat meat to eat vegetarian, it is necessary to grow a larger body, so as to accommodate a larger stomach. In addition, the body temperature of vegetarian animals also needs to reach the high temperature required for microbial activity. In short, before eating vegetarian food, it is necessary to grow into a carbon-based Petri dish, which is a very harsh condition for the lizard of the temperate animal.
The digestive tract (powder) of ruminant cattle is large. Image source: wikimedia
So why are these Italian wall lizards suddenly able to digest vegetarian food?
It turns out that they grew an intestinal structure that their ancestors did not have - the gyrus blind valve.
The ileophilic blind valve consists of a sphincter.
The structure of the gyrus blind valve is a sphincter muscle valve that regulates the digestion rate of food, allowing intestinal bacteria to ferment the plant for sufficient time to convert it into fatty acids that lizards can absorb and utilize.
The gyrus blind flap itself is not a new product in evolution, but it is rare in the wall lizard family. In fact, less than 1% of the scaly lizards to which the Italian wall lizard belongs have a ileocity valve. Although other vertebrates, such as Fat Da, have been recorded as carnivorous to vegetarian, this rarely happens in squamous lizards.
In other words, the Italian wall lizard evolved a new body structure in up to 30 generations and 37 years, and changed from carnivorous to vegetarian. Irschick makes an analogy: It's as if humans have grown a new appendix (the original function of the appendix is a plant fermentation tank) within a few hundred years.
The position of the appendix. Image source: wikimedia
In order to be vegetarian, their bodies not only grew new sphincters, but also "outsourced" the work of handling plants to their supporting teammates: a belly "clam". In fact, the intestines of the Bod-Makaru wall lizard are full of bacteria and nematodes that digest plant fiber, but their hometown lizards of the same breed do not, which is also surprising.
Of course, in order to better "graze", the heads of these lizards have become larger and wider, and their bodies have become larger as the theory predicted.
The researchers comment that, in general, it takes millions of years to completely change your diet. But it took these lizards less than 40 years to adapt to the environment, which can be said to be very strange. Irschick said: "This rate of evolution is unprecedented. Andrew Hendry, a biologist at McGill University in Canada, agrees: "The change is amazing. ”
Changes in the body also bring about changes in behavior and group structure. No longer need to pursue their prey, their hind legs become shorter and slower. Moreover, now that everyone loves to eat "grass" and there are many plants on the island, these lizards have weakened their territorial awareness and live closer, and they have produced more small lizards, making the population density very high.
Changes in the body of the Italian wall lizard have also upset the local ecological balance. During the italian wall lizard's transition to vegetarianism, the island's original lizard community was completely defeated. Although the researchers do not know how this process occurs, exotic lizards now completely occupy the habitat of native lizards.
This amazing study was published in the Proceedings of the National Academy of Sciences (PNAS) in 2008. The discovery also changed the researchers' understanding of evolution. The paper suggests that rapid evolution may be a universal phenomenon, rather than a rare exception, as traditional Darwinism believes.
However, the guy who can evolve into a vegetarian in 40 years is inevitably too flexible and stretched, right? When it comes to the place where the meat dishes are shook in the face, can they still be so calm?
Some researchers have begun to wonder how to make these little guys "break the ring" and start eating meat again. Once again, the results of their experiments startled the researchers.
Italian wall lizard (Podarcis siculus). Image source: wikimedia
In 2010, researcher Bart Vervust and colleagues at the University of Antwerp in Belgium published a series of experiments they had done. Over 15 weeks, they fed arthropods (such as insects) to the captured Bode-Makalu Italian wall lizards to see if their bodies would change. Apart from "meat", these wall lizards do not eat any vegetarian dishes.
As a result, the intestines of these lizards became shorter, and the gyrus blind flap even disappeared directly. It turns out that for the Italian wall lizard, this time the blind flap can be switched on and off at will.
In fact, the back blind flap "summoning" may be just a small skill for the Italian wall lizard. Their extreme adaptability has long been studied.
For example, although the Italian wall lizard comes from the dry and hot Mediterranean region, they are able to adapt to the -20 degree Celsius winter on Long Island, New York, and spread to many parts of North America.
This is because they can perform advanced versions of hibernation: let the water in the body directly into the super-cold (below freezing point) state without freezing, and sleep directly through the winter through this "whole machine protection mode".
Slight disturbance of excessive cold water is prone to icing.
They are also good at copying homework to learn. A 2018 study published in Biology Letters found that they could not only apply the experience of the same lizard species, but even learn from lizards of different species, find plastic boxes containing food, and open the lid to remove the food.
In this way, fat Dajun, who has forgotten that the taste of meat can only nibble on bamboo poles, has to work hard.
Vegetarian animals have large heads and large bellies and high body temperatures, and it seems that vegetarians cannot lose weight.
Cover source: pxhere
Resources:
https://docs.qq.com/doc/DVFJqSkVjc1NVUWVL
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