• Gynogenesis

     A method of reproduction in which the sperm, penetrating the egg, only stimulates its development, its nucleus does not merge with the nucleus of the egg and does not participate in the subsequent development of the embryo. An organism with a haploid set of chromosomes emerges, and there are only females in the offspring. Silver carp eggs are inseminated by the sperm of other fish species - pike, carp, tench, and even goldfish. Gynogenesis can be induced artificially, using chemicals, X-rays and other rays, and abrupt temperature changes and many other factors.
     The role of the sperm is limited to the activation of the inseminated egg to develop. In nature, gynogenesis is extremely rare. It is known in several species of fish (the holomyanka, silver carp, Amazon mollinsia, etc.). Experimentally, gynogenesis can be obtained by inseminating eggs with the sperm of distant species, by inactivation of the sperm nucleus by physical and chemical agents, or by mechanical removal of the male pronucleus from the egg. The haploid embryos that develop in this process are usually non-viable. Gynogenesis is used to produce strictly homozygous organisms as well as individuals of the same, usually female, sex. To obtain diploid gynogenesis, the cytotomy of one of the divisions of oocyte maturation or one of the first divisions of egg crushing must be suppressed. An obsolete synonym for gynogenesis is merospermia (failure of the sperm nucleus to fuse with the egg nucleus after penetrating it, which is one of the main causes of gynogenesis).

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