Due to a scientist's mistake, two species accidentally merged and became a creature no one has ever seen before

Regarding the publicity for protecting wild animals, many people remember the phrase "no business, no killing", and many people still remember the public service advertisements shot by CCTV. A huge clock appeared in the advertisement, and the position of each moment on the clock corresponds to an extinct creature, such as the dodo, moa, thylacine, Antarctic wolf, etc. Every time the pointer passes over a creature, the species Extinct, and the hour hand finally points to human beings.

This advertisement is thought-provoking. In the past 100 years, hundreds of species have disappeared on the earth, and most of the disappearance of species is related to human activities. In short, humans are not the culprit. , is also an indirect cause. Therefore, if you want to save some endangered species, you must reduce the impact of human activities on them. A common method is to establish nature reserves. However, some species have some problems in reproduction and need artificial help to reproduce, such as the national treasure panda.

In foreign countries, there are two kinds of sturgeon that are also endangered, they are the Russian sturgeon and the American white sturgeon. In order to save the two species of sturgeon, scientists conducted a parthenogenesis experiment, which happened unexpectedly, resulting in a hybrid species of the two species. So how did this accident happen? Can the new species formed by hybridization also reproduce?

What is the difference between Russian sturgeon and American white sturgeon?

First let's learn about Russian sturgeon and American white sturgeon. Russian sturgeon originated in Russia, and was later introduced into artificial culture by many countries. Russian sturgeon was introduced in Northeast my country. According to the data, the Russian sturgeon has a body length of about 2.3 meters, a weight of 110 kilograms, and a general life span of 50 years. The most obvious feature of the body surface of the Russian sturgeon is that its back has multiple dorsal bony plates, the number of which is between 8 and 18.

American white sturgeon is a large sturgeon distributed in the United States. Adults can grow to about 6 to 9 meters in length and weigh more than 680 kilograms. It is currently the longest freshwater fish in the world. In fact, a large part of the body length of the American white sturgeon is contributed by its snout, which is one of the most obvious characteristics of it and the Russian sturgeon. Comparing the two species of sturgeon, the American white sturgeon survived in body length and outperformed the Russian sturgeon in snout length.

But in terms of its importance to the cuisine, the Russian sturgeon may be more important, because the raw material in the caviar comes from the roe of the Russian sturgeon. In the end, both sturgeon species have one thing in common, which is that they are now endangered. Russian sturgeon has always been the object of fishermen's catch, people get roe and meat from it, and the meat of American white sturgeon is also pursued by many Americans, so overfishing has led to the survival of these two sturgeon is not optimistic. .

What makes it so difficult for sturgeon to survive?

It is understood that the Russian sturgeon belongs to the river-sea migratory fish, mainly distributed in the Azov Sea, the Black Sea and the Caspian Sea. River-sea migratory fish means that the fish to be produced will swim to the upper reaches of the river to spawn. These fish eggs will move downstream along the river in the upstream, and finally enter the sea to develop and grow. When they need to produce, they will migrate to the river again. Spawn upstream. Fishermen in the Azov Sea, Black Sea and other regions have mastered this feature of Russian sturgeon and ambushed them at certain times of the year.

Some fishermen catch not only Russian sturgeon, but also his freshly laid eggs. This approach has almost wiped out all the possibilities of a sturgeon for the reproduction of the population, and the Russian sturgeon has gradually fallen into a disadvantageous situation in the long run. Although the American white sturgeon is not as dangerous as the Russian sturgeon, its meat is so delicious that humans are willing to kill it for its meat.

In addition to human activities that have put the two species of sturgeon in an endangered situation, the rate of reproduction of the sturgeon itself is also a problem. Sturgeons generally have a lifespan of several decades, but they have only a few chances to produce offspring, and the survival rate of each egg is not high. Therefore, if they only rely on their own efforts in nature, they may inevitably go to extinction, so many scientists have proposed artificial help for the endangered sturgeon.

What method have scientists come up with to save these two species of sturgeon?

There are currently two main ways to save endangered animals: taking conservation measures and increasing reproductive opportunities. In terms of protection measures, we can establish nature reserves, improve the habitat of living things, and issue relevant protection policies and decrees. In terms of increasing the chance of reproduction, it is necessary to carry out artificial cultivation experiments in the laboratory in advance. In order to improve the living conditions of Russian sturgeon and American white sturgeon, some scientists have proposed the concept of "parthenogenesis".

The so-called parthenogenesis refers to the use of sperm close to the egg, and then let the sperm induce the egg to produce mitosis and meiosis, and then evolve into an embryo. In this process, the sperm does not fuse with the egg, so this method of asexual reproduction is called "parthenogenesis". There have been many cases of saving endangered animals that have used parthenogenesis, and finally achieved good results. Therefore, scientists believe that parthenogenesis can be tried on Russian sturgeon and American white sturgeon.

So scientists took eggs from Russian sturgeon and sperm from American white sturgeon, and cultured them in special containers. During the experiment, scientists observed that the sperm of the white sturgeon did work on the eggs of the Russian sturgeon, but in the end the two fused together. In other words, the original parthenogenesis experiment became a sexual reproduction hybrid experiment of two sturgeons. The scientists did not interrupt the experiment, but observed the final experimental results.

Finally, the experimental results showed that the Russian sturgeon was successfully fertilized and hundreds of hybrid fry were produced. For this result, all the scientists involved in the experiment expressed surprise, because in theory there is reproductive isolation between the Russian sturgeon and the American white sturgeon, and the reproductive cells of the two cannot be fused together, so they are also surprised by the unexpected phenomenon in the experiment. confused. But there are also some similar cases in reality, such as horses and donkeys giving birth to mules, as well as Russian sturgeon and American white sturgeon.

What does a new sturgeon from crossbreeding look like?

According to the introduction of the research team, they cultivated hundreds of fry produced in the hybridization experiment, and finally cultivated most of the fry to adults. From the appearance of these hybrids, they are more similar to the Russian sturgeon, for example, they have the same back and mouth as the Russian sturgeon, but inherit the fins and snout of the American white sturgeon. In terms of diet, hybrid fish and Russian sturgeon are carnivores.

Scientists conducted an in-depth analysis of the hybrid fish's genes and found that those individuals that resembled the Russian sturgeon in appearance actually inherited double the DNA of the Russian sturgeon. However, some individuals obtained almost the same amount of DNA from Russian sturgeon and American white sturgeon, so they have the characteristics of both in appearance. Some friends may be concerned about a question, can these hybrid offspring produce delicious roe like Russian sturgeon?

This question is currently unsolved, because it is impossible for researchers to dissect them in order to obtain the answer to this question, compared with other aspects of research have more value.

Will scientists continue to create new sturgeons?

Since the germ cells of Russian sturgeon and American white sturgeon can hybridize to form embryos, could this approach improve the endangerment status of both species? Scientists think it's unlikely because of two problems. The first problem is that the survival rate of the hybrid offspring of the two sturgeons is relatively low. Although hundreds of fry were born in the hybrid experiment mentioned above, under artificial cultivation conditions, 70% of the fry died after one month, leaving about a hundred fry.

These fry may also die in subsequent breeding, so the survival rate of hybrid fry is less than 50%. The second question is whether the hybrid fry can reproduce normally. Although scientists have not conducted relevant experiments yet, their theoretical answer is that offspring cannot be reproduced normally. Take a mule as an example. Although it is a hybrid offspring of a horse and a donkey, it cannot reproduce under natural conditions, because its chromosome pair number is abnormal and cannot be paired normally.

From this point of view, it is not feasible to expand the population of the two sturgeons by hybridization, and scientists may need to re-implement a more rigorous parthenogenetic method.

Why is Chinese sturgeon a living fossil? Why does it fall into the predicament of survival?

In fact, in addition to the Russian sturgeon and the American white sturgeon, my country's Chinese sturgeon is also an endangered species, and the endangered situation is even more serious than those two sturgeons. Modern biologists define the Chinese sturgeon as a "living fossil", the main reason is that this species has a history of 150 million years, and its evolution rate is very slow, and it still retains many characteristics of Mesozoic marine creatures, so humans can Obtain information on marine life in the Mesozoic period by studying its body surface and structure.

There are data records that since the 1970s, the number of Chinese sturgeons in the Yangtze River Basin has only been more than 10,000. In the 1980s, when Gezhouba was blocked, the number of Chinese sturgeons plummeted to more than 2,100. It has just entered the 21st century. There were only 363 left in 2010, and only 57 in 2010. The reasons for the endangerment of Chinese sturgeon are actually not difficult to understand. One is water pollution, the other is the early overcapture, and the third is the construction of water conservancy projects.

At the beginning of last year, it was reported that the Chinese sturgeon was close to extinction, and the situation was very critical. If this species eventually became extinct, it would be another typical case of human beings' negative impact on natural creatures.