Sterility is the loss of reproductive power due to any reason leads better growth and food conversion efficiency. A huge energy is utilised for gonadal maturation and production of gametes in fish. If the sexual maturation is stopped the fish can grow more rapidly. The all foods supplied in that case are transferred to the flesh and no wastage of food or energy for gonadal maturation can be seen in sterile fish. Not only this, sterility avoids prolific reproduction and over crowding of fish. Sterile fish can be produced in various ways –
Induction of autoimmunity of gonads
Extirpation of gonads
Chromosomal manipulation for production of polyploidy
Hybridization
Hormonal sex reversal to super males and super females of giant sized fish
Non hormonal chemicals which can sterile fish
Exposure to UV rays or radioactive substances
Among the above mentioned process hormonal sterility is applied in case of sterile fish production where insufficient application of male hormone or female leads partial change of male to female or female to male and can produce sterile fish. The method is very easy but not acceptable in all countries because hormone treated fish is bad for human consumption.
Non hormonal chemicals like methallibure or cyproterone acetate. Both these are chemosterilants can reduce Gonadotropin production and lower androgen secretion, but do not prevent the gonad maturation. These drugs will have to be administered to the young fry in their diet; hence the utility in commercial purpose is doubtful.
Hybridization of some species can produce sterile fish which is very easy, economical and no doubt to human consumption.
Exposure of fish or fry in UV rays or any other radio active radiation cause gonadal destruction leads to the sterility of fish. The method needs well equipped laboratory with very much experienced workers. The production of such type of sterile fish is not encouraged in commercial purpose.
Polyploidy (Broiler Fish): It is one of the methods to produce sterile fish most easily. The triploid can be achieved experimentally by chromosomal manipulation brought about the suitable exposure to thermal or hydrostatic pressure shock at early stages of development. The mechanism involved to prevention of second polar body from the eggs.
Triploid can produce by a cross between the female common carp and rohu are sterile by following way:
By intergeneric mating between a diploid female of one species (any IMC, for example) and triploid male of another species (common carp)
Induction of autoimmunity of gonads
Extirpation of gonads
Chromosomal manipulation for production of polyploidy
Hybridization
Hormonal sex reversal to super males and super females of giant sized fish
Non hormonal chemicals which can sterile fish
Exposure to UV rays or radioactive substances
Among the above mentioned process hormonal sterility is applied in case of sterile fish production where insufficient application of male hormone or female leads partial change of male to female or female to male and can produce sterile fish. The method is very easy but not acceptable in all countries because hormone treated fish is bad for human consumption.
Non hormonal chemicals like methallibure or cyproterone acetate. Both these are chemosterilants can reduce Gonadotropin production and lower androgen secretion, but do not prevent the gonad maturation. These drugs will have to be administered to the young fry in their diet; hence the utility in commercial purpose is doubtful.
Hybridization of some species can produce sterile fish which is very easy, economical and no doubt to human consumption.
Exposure of fish or fry in UV rays or any other radio active radiation cause gonadal destruction leads to the sterility of fish. The method needs well equipped laboratory with very much experienced workers. The production of such type of sterile fish is not encouraged in commercial purpose.
Polyploidy (Broiler Fish): It is one of the methods to produce sterile fish most easily. The triploid can be achieved experimentally by chromosomal manipulation brought about the suitable exposure to thermal or hydrostatic pressure shock at early stages of development. The mechanism involved to prevention of second polar body from the eggs.
Triploid can produce by a cross between the female common carp and rohu are sterile by following way:
By intergeneric mating between a diploid female of one species (any IMC, for example) and triploid male of another species (common carp)
By subjecting the fertilised eggs involving the egg of one species and sperm of another, to the action of antibiotic cytochalasin or colchicines which are mitotic inhibitor & so disrupt the first cleavage mitosis. By subjecting the normally fertilised eggs, involving artificial insemination of egg of one species (common carp) by the sperm of another species (rohu), to heat cold or hydrostatic pressure shocks. The shocks suppress the release of 2nd polar body (i.e. early metaphase of meiosis II).
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