Scientists have uncovered the secrets of fish survival, completely abandon sex

CC0 / Vassil / Fish-rivulus that reproduce by immaculate conceptionScientists have uncovered the secrets of fish survival, completely abandon sexCC0 / Vassil /

Unusual tropical fish-rivulose, reproducing by «immaculate conception» for several million years until they became victims of diseases and parasites due to the unusual mechanism, which protects them from degeneration, according to a paper published in the journal Genome.

«We found that some DNA regions of these fish was unexpectedly spotted with the genetic point of view, which was a surprise to us, given their method of reproduction. This has opened a Pandora’s box and made us think about how this could happen,» says Luana Lins (Luana Lins) from Washington state University in Pullman (USA).

Some living creatures, for example lizards, chickens or many insects are capable of parthenogenesis — pregnant, in which two eggs are fused together, forming the embryo, or cell spontaneously begins development, despite the «half» set of chromosomes. For mammals, this method of reproduction is quite typical, and there is no one type of animal that would be able to do this even in theory.

The fact of the existence of these creatures that reproduce by «immaculate conception» is a mystery to evolutionists. Refusing to have sex and exchange genes with other dogs, these animals become vulnerable to parasites that, in accordance with the hypothesis of the red Queen, in this case develop faster than their victims.

Therefore, as believed by scientists, such «asexual» species should exist only for a short time, however, practice shows that many of them exist already tens of millions of years. Lins and colleagues revealed the secrets of survival of one of the most unusual of their representatives, tropical fish-rivulus (Kryptolebias marmoratus), the deciphering of its DNA and observing the process of its reproduction.

These inhabitants of the waters of the Amazon, as the scientists explain, not yet completely lost the ability to sexual reproduction. The vast majority of these fish is a hermaphrodite, however, extremely rare among them there are males can only impregnate, but do not produce eggs.

Analyzing the DNA of these fish, Lins and her colleagues expected to see both parts of its DNA is composed of approximately the same genes that were inherited from a common ancestor, who moved from sex to «the immaculate conception». In reality this was not the case — despite the high level matches, many regions of its genome, especially those related to the immune system, were made of very different sets of genes.

Such differences in the structure of genes, how do you think genetics help these fish to adapt to new pests and changes in living conditions, which may explain why they are still not extinct.

What is even more interesting, this anomaly, as the researchers note, may not result from accelerating the accumulation of mutations in the genome – in this case they would be located randomly, and not concentrated in certain parts of the DNA. Trying to understand how they arise, biologists have studied the results of observations of the reproduction of rivulus that conducted by other scientists.

They showed that the «authors» of all of these unusual genes can be a few male fish are hermaphrodites prefer to interbreed with them and not fertilize their own eggs, and in such cases, they leave more offspring, especially when his father comes from another group of rivulus. This theory Lins and her colleagues will test soon, comparing the structure of DNA «clones» of one mother and representatives of the other fish populations.