What does cloning mean
Asexual propagation and the formation of asexual propagation
Identical offspring individuals. It’s usually made by biotechnology
To produce an individual or population with exactly the same gene as the original. It may be hard for people to imagine that without the laboratory, cloning still exists in nature, and even “self” unlimited reproduction in this way has become a headache ecological disaster.
Current status of new species of marbled catfish
Crayfish is very common in life, we often eat crayfish also known as
And crayfish. Crayfish is easy to raise, pollution-resistant, food miscellaneous, so all over the breeding. China was introduced from Japan in the 1930s-1940s, and Japan was introduced from the United States earlier, mainly for food and pets. Although its strong survival ability is an advantage for farmers, once the crayfish escape, it will pose a huge threat to the local ecological environment.
February 8, 2018 according to reports, in order to survive, organisms will use gene mutation to adapt to the environment. A variant crayfish called marbled crayfish has the ability of self cloning caused by gene mutation. In the past 25 years, its offspring have invaded all over Europe
In the 1990s, a female crayfish was born in a common aquarium. On the outside, it’s bigger and lays more eggs. The most amazing thing is that she can parthenogenesis, that is to say, without mating with the male crayfish, her own eggs can develop into a complete individual independently, which is unprecedented in the crayfish population. In 2017, scientists identified it as a new species, the marbled shrimp.
Marbled crayfish have been blacklisted in many areas, including the European Union and parts of the United States, and their damage to freshwater ecological resources is incalculable.
First of all, compared with ordinary crayfish, it retains the advantages of miscellaneous food, strong stress resistance and heavy metal environment, and increases the advantages of large size, more eggs and self reproduction, reducing the risk of being hunted when mating. Its invasion brought great threat to species in Madagascar, Germany, Czech Republic, Hungary, Croatia, and then Japan. The local fishery, aquatic plants and clam seedlings are reduced to their food, resulting in countless economic losses.
However, in other words, the invasion of marbled crayfish is mainly due to the curiosity of aquarium lovers. A large number of enthusiasts buy this kind of magic crayfish home, but it often takes less than a year, and this kind of crayfish with strong breeding ability will be flooded, so many owners who are unable to raise them will pour them into the river. With the east wind of economic globalization, they gradually “invade” European countries.
What’s more dangerous is that crayfish marbling crayfish can carry crayfish pestilence fungi. Although the pestilence fungi will not cause harm to themselves, they will be a devastating blow to native crayfish. In just a few days, the shrimp plague fungus can cause a large number of crayfish to die. Therefore, their harm is not only to the local fish, shrimps and aquatic plants, but also to the same kind of competition. Like crayfish, they can survive in a wide temperature range and are very tolerant to pH. However, in the environment of high salt concentration, their reproduction and survival will be greatly affected.
Parthenogenesis of marbled catfish
In the past two decades, biologists have sequenced the genome of crayfish marbled. The results showed that it was probably the offspring of two different crayfish. It is also worth mentioning that the gene arrangement of all crayfish is almost identical. In other words, all marbled crayfish come from the self replication of the original mutant female.
At the beginning of the 21st century, scientists confirmed that the marbled crayfish was indeed parthenogenetic, and the gene sequence showed that the parent was a. gigas. Parthenogenesis is also called parthenogenesis
That is to say, the egg cells can develop into new normal individuals without fertilization. Parthenogenesis is a common phenomenon in some primitive animal species. However, it is occasionally found in vertebrates, such as the spitting ribbon in birds. However, parthenogenesis has never occurred in crayfish.
Scientists have done experiments to determine whether marbled crayfish are permanent parthenogenesis or sporadic parthenogenesis. The content of the experiment is to raise marbled crayfish and male dragon crayfish together to observe whether they can produce offspring. In the experimental tank, the two crayfish did have mating behavior, and the holding time was about one hour. Unfortunately, the genes of the offspring of crayfish marbled after mating were still the same as those of crayfish marbled. That is to say, crayfish marbled cannot mate with males to produce fertile offspring. Based on this, the scientists listed crayfish marbled as an independent species.
In order to explain this sudden variation, scientists have done a lot of research, and found that crayfish marbled has three sets of chromosomes, while crayfish ordinary has only two sets of chromosomes, which is called diploid from the biological point of view. That is to say, the reason why marbled crayfish can only reproduce by itself is that its extra set of chromosomes can’t pair with the chromosomes in male sperm.
Scientists speculate that this may be because when the male or female parent of crayfish produced germ cells, due to low temperature or other reasons, the germ cells that should have only one chromosome divided abnormally and contained two chromosomes. When the sperm and egg cells combined, triploid individuals were produced. As for why the extra chromosomes didn’t affect their life activities, scientists have no way to know. Maybe they can only sigh about the magic of the creator. Parthenogenesis may sound like breaking down many barriers to sexual reproduction, and it is enviable that an independent individual can reproduce the next generation. However, in fact, the vast majority of asexual creatures in the world are far behind the sexual ones in evolution. It is because of sexual reproduction that the gene combination of two different parents greatly increases the chance of gene mutation, provides more possibilities for biological evolution, and reduces the harm of genetic diseases to the whole population. In the long run, this kind of marbling crayfish, which makes people headache, may be extinct in tens of thousands of years because of a small opportunity.
This phenomenon has also occurred in humans, often due to multiple sperm fertilization at the same time lead to mixed ploidy embryos, but this kind of embryo can rarely develop normally. Even birth is accompanied by physical deformities or mental disorders.
However, no one knows why the two unpaired chromosomes can successfully complete fertilization and individual development, and no one knows why the extra chromosomes did not cause the female crayfish to die abnormally.
Can eating solve the problem of marbling shrimp?
Marbled crayfish has not yet appeared in the wild environment of China, but many netizens who have heard of its existence have begun to ask questions: can we solve the problem of invasive species by eating it? Whenever we hear about alien invasive species, there are always people eager to try, trying to solve the problem of invasive species by eating. We must say that we should not be confused by official account. Invasive species such as bullfrog, tilapia, even though delicious, are also rampant. In order to eliminate the economic losses caused by water hyacinth, how much manpower and material resources has China paid.
First of all, although marbled crayfish is edible, its taste and meat yield are not as good as those of Procambarus clarkii. As mentioned earlier, marbled crayfish are large in size, but also compared with dragon crayfish. The body length of Procambarus clarkii can reach 5.5-12 cm, which is larger than that of crayfish marbling. On the contrary, if marbled crayfish is introduced, the loss it brings is immeasurable.
In Madagascar, the worst hit country, the poor grab crayfish, a cheap protein supplement. In fact, in the wild environment, small lobsters often eat rotten fish and shrimps or toxic substances with high content of heavy metals because of their miscellaneous food. Therefore, this kind of crayfish is still listed as “low economic value” in the world and should not be introduced.
The more serious consequence is the harm of crayfish marbling to species diversity. For other animals and plants, when they enter the rice fields, the roots of the rice seedlings are their favorite food. The rice fields will greatly reduce their output, and the blow to the local fisheries will also be fatal – the fry are also in their diet. For the local crayfish, the invasion of marbled crayfish will seize the original resources and reduce the living space. In Madagascar, the range of the crayfish has increased from 1000 square kilometers to 100000 square kilometers in the last decade, more than 10 times. Today, the population density has threatened seven native wild crayfish species in Madagascar.
European countries and parts of the United States have listed marbled crayfish as “forbidden.”. It is forbidden for people to smuggle, raise and release marbled catfish in the wild. At present, China has not issued relevant laws and regulations, but if you raise this kind of crayfish in your family, please don’t release it everywhere or fish with its live bait. Inadvertent behavior may cause damage to the ecological environment. In general, the introduction of marbling crayfish is tantamount to introducing wolves into the house.
Crayfish marbling has many rare properties in biology. We may make use of this kind of variation to study its genetic law, character performance and development process, and apply the experimental results to benefit human beings.