The ancestors of goldfish invented the original mechanism of aging
At present, the generally accepted version of the origin of numerous goldfish breeds is the domestication of its ancestral form in China in about the 7th century AD. According to this theory, the source material for breeding was the individuals of the Chinese subspecies of the crucian carp (Carassius auratus auratus) living in southern China. However, the “authorship” of the creation by the Chinese of a goldfish may be questioned, due to the discoveries of possible wild ancestors of the domesticated goldfish ... in the waters of South - Eastern Europe.
If you think that goldfish are born gold, you are mistaken. The fry of a goldfish up to the age of 1-2 months looks rather modest: it is an ordinary silver-gray fish. Then the back darkens, spots appear, the color is increasingly changing in the direction of gold and red. In domesticated goldfish breeds, such a "molt" occurs rather early, even before the onset of puberty. This is beneficial to breeders: you can quickly select the best options for coloring. The sex of domesticated goldfish is genetically determined: males come from some eggs, females from others. There are also no known cases of sex change - during the life of the males remain males, and females - females.
At the beginning of the 21st century, the well-known Russian ichthyologist Sergey Borisovich Pillow in the North Caucasus discovered the wild form of a goldfish, which he later called the commercial goldfish (PZR). pandia.ru/text/78/119/113166.phA
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For a number of years, Sergey Borisovich has been studying PZR in aquaculture. It turned out that this form is gynogenetic, represented in nature only by females. Gynogenesis is a form of reproduction in which the egg develops without fertilization, and the sperm cell serves only as a stimulus for the beginning of its development. The mere fact that PZR is a gynogenetic form suggests an idea of ​​its natural origin. Indeed, among the many breeds of goldfish, gynogenetic forms are not known. Crossing of a domesticated goldfish with goldfish when it hit the first one in natural water bodies repeatedly occurred, but there were no cases of parthenogenesis in such hybrids. Subsequently, it became clear that part of the PZR in the process of individual development can "turn" into males. Males showed normal "masculine" behavior, chasing females during spawning. However, it turned out to be almost sterile. The transformation of females into males in fish is not something extraordinary - in the experiment this is done by adding to the water the corresponding sex hormones, for example, testosterone. But the males at the same time are completely fertile, with normal spermatogenesis.
As a result, the PZR males lost their fertility? A plausible version seems to be that over many generations of clonal reproduction, natural selection did not affect the genes associated with spermatogenesis, and as a result of accumulated spontaneous mutations, these genes were simply “spoiled”. Thus, by the number of mutations accumulated during the period of clonal reproduction of PZR in certain genes, and knowing the rate of spontaneous mutagenesis in these genes, one can determine the age of origin of this form.
What about color changes? PZR "molt" at the age of 3 - 4 years, and very unevenly, some earlier, others later. And some may retain the original silver - gray color for a few more years, but at the same time they become sexually mature at the age of the year.
It can be assumed that the color change in the PZR is an adaptation that makes it possible to more efficiently use the limited forage resources of small, and often drying, steppe reservoirs, in which PZR could live. The larger fish that changed color to red were predators, as a result of which relatively small but already mature and numerous silver-gray fishes gained an advantage in the continuation of the genus.
We see a similar adaptation in many plants: when the seeds are ripening, the fruits gradually acquire a bright color, as if inviting various animals: “Eat me!”
Such adaptation in PZR is not beneficial for a single individual, but allows a successful population to exist as a whole. It could appear as a mutation in one or several individuals in a small closed population. If clonal reproduction occurred earlier than the ability to change color, the absence of intrapopulation mating could support the spread of this mutation.
Unfortunately, there are no answers to all the questions raised. And this is greatly facilitated by the secrecy that has arisen around the topic of PZR. Numerous publications by S. B. Pillows are slowly disappearing from the Internet. Aquaculture PZR transferred to the All-Russian Research Institute of Fisheries and Oceanography (VNIRO), and now about it for several years, "no rumor, no spirit." Nobody knows what VNIRO specialists found in the PZR, why there are no publications at least in Russian.
The phenomenon of a commercial goldfish may prove to be worthy of publication in prestigious scientific journals, such as Nature, and shed light on many questions concerning the occurrence of gynogenesis, evolution and aging of organisms.
If you think that goldfish are born gold, you are mistaken. The fry of a goldfish up to the age of 1-2 months looks rather modest: it is an ordinary silver-gray fish. Then the back darkens, spots appear, the color is increasingly changing in the direction of gold and red. In domesticated goldfish breeds, such a "molt" occurs rather early, even before the onset of puberty. This is beneficial to breeders: you can quickly select the best options for coloring. The sex of domesticated goldfish is genetically determined: males come from some eggs, females from others. There are also no known cases of sex change - during the life of the males remain males, and females - females.
At the beginning of the 21st century, the well-known Russian ichthyologist Sergey Borisovich Pillow in the North Caucasus discovered the wild form of a goldfish, which he later called the commercial goldfish (PZR). pandia.ru/text/78/119/113166.phA
')
For a number of years, Sergey Borisovich has been studying PZR in aquaculture. It turned out that this form is gynogenetic, represented in nature only by females. Gynogenesis is a form of reproduction in which the egg develops without fertilization, and the sperm cell serves only as a stimulus for the beginning of its development. The mere fact that PZR is a gynogenetic form suggests an idea of ​​its natural origin. Indeed, among the many breeds of goldfish, gynogenetic forms are not known. Crossing of a domesticated goldfish with goldfish when it hit the first one in natural water bodies repeatedly occurred, but there were no cases of parthenogenesis in such hybrids. Subsequently, it became clear that part of the PZR in the process of individual development can "turn" into males. Males showed normal "masculine" behavior, chasing females during spawning. However, it turned out to be almost sterile. The transformation of females into males in fish is not something extraordinary - in the experiment this is done by adding to the water the corresponding sex hormones, for example, testosterone. But the males at the same time are completely fertile, with normal spermatogenesis.
As a result, the PZR males lost their fertility? A plausible version seems to be that over many generations of clonal reproduction, natural selection did not affect the genes associated with spermatogenesis, and as a result of accumulated spontaneous mutations, these genes were simply “spoiled”. Thus, by the number of mutations accumulated during the period of clonal reproduction of PZR in certain genes, and knowing the rate of spontaneous mutagenesis in these genes, one can determine the age of origin of this form.
What about color changes? PZR "molt" at the age of 3 - 4 years, and very unevenly, some earlier, others later. And some may retain the original silver - gray color for a few more years, but at the same time they become sexually mature at the age of the year.
It can be assumed that the color change in the PZR is an adaptation that makes it possible to more efficiently use the limited forage resources of small, and often drying, steppe reservoirs, in which PZR could live. The larger fish that changed color to red were predators, as a result of which relatively small but already mature and numerous silver-gray fishes gained an advantage in the continuation of the genus.
We see a similar adaptation in many plants: when the seeds are ripening, the fruits gradually acquire a bright color, as if inviting various animals: “Eat me!”
Such adaptation in PZR is not beneficial for a single individual, but allows a successful population to exist as a whole. It could appear as a mutation in one or several individuals in a small closed population. If clonal reproduction occurred earlier than the ability to change color, the absence of intrapopulation mating could support the spread of this mutation.
Unfortunately, there are no answers to all the questions raised. And this is greatly facilitated by the secrecy that has arisen around the topic of PZR. Numerous publications by S. B. Pillows are slowly disappearing from the Internet. Aquaculture PZR transferred to the All-Russian Research Institute of Fisheries and Oceanography (VNIRO), and now about it for several years, "no rumor, no spirit." Nobody knows what VNIRO specialists found in the PZR, why there are no publications at least in Russian.
The phenomenon of a commercial goldfish may prove to be worthy of publication in prestigious scientific journals, such as Nature, and shed light on many questions concerning the occurrence of gynogenesis, evolution and aging of organisms.
Source: https://habr.com/ru/post/453820/
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