Production Process of Triploid in Fish_Syekat Fish World

Triploids are fish that have three sets of chromosomes . Triploidy has been induced in a variety of fish species and is of interest to aquaculturist .Because it results in functional sterility and increased growth.There are two method for producing triploid in fish .They are mention below:

First Method:

Triploids are created by shocking newly fertilized eggs , shortly after fertilization .Fish eggs do not extrude the second polar body until they are fertilized . Because of this if a newly fertilized egg is shocked ,the shock prevents the second polar body from leaving the eggs. As a result the fertilized eggs contain three haploid nuclei (one from the eggs ,one from the sperm & one from the second polar body ) .The three haploid nuclei will fuse in form of a triploid(3N ) zygote nucleus.

Fig: Disruption of cellular process associated with meosis-ll ,causing retention of seond polar body .For triploidy the retention of second polar body causing the formation of nucleus with three sets of chromosomes.

Second Method:

Triploid can also be produced by crossing between a tetraploid and diploid.Tetraploid Rainbow trout have also been crossed with diploid to produce triploid.These progeny are referred to as a interploid-triploids.Because no shocked are applied for this system.This method appears to be reliable and avoids detrimental side effects associated with conventional methods of triploidy induction.

Fig:The production of interploid-triploid is achived by fertilization of a haploid egg from diploid female and with a diploid sperm from tetraploid male.

Triploid Are Sterile

In triploid organisms,gametic incompatibility occurs during meosis.Because triploid has three sets of chromosomes.These chromosome can not properly pair align themselves ,which make it difficult to undergo meosis.Because the chromosomes can not be divided into two equal haploid sets.Gametes that are produced are usually ancuploid and they contain unbalanced number of chromosomes. [If ancuploid gamets are formed, they produced abnormal and sub-viable offspring that do not live long .So, triploid are sterile.] 

Triploid Are  Best Grower

On the other hand triploid have an increased DNA size,nucleur size,number of chromosomes and cellular size compared to diploid.Besides the nucleus of triploids contain 33% more allele for growth .And triploids do not driven their energy for growth to gamete production , reproduction or care of young .So triploids have faster growth than others.

Significance of Triploids Production

ü 1. Triploid produce sterile fish .So the species that might cause adverse environmental impacts can be cultured on farms or used in natural resource management.

ü  2.The production of sterile fish can reduce the risk of exotic introduction and contamination wild gene pools.

It 3.It can be safeguard against unauthorized perpetuation of transgenic genomes and project intellectual property.

   4.The development of sterile stocks for food fish producton can be used to control  precocious spawning in fishes that reach market size and may improve growth.

    5.Higher growth rate.

    6.Species with early maturity.

Nazmul Haque Syekat

Fisheries & Marine Science ,NSTU