Originally Posted by
Tom
LOL we are not allowed the truth as to why
now hands up please
Update just found this a study of Triploids.....they may still upset spawning runs
Triploid Trout:
I was recently very surprised to learn that Triploid Trout can develop gonads. What
exactly is Triploid Trout or Salmonids then and what are the benefits of using them in
aquaculture production systems?
Triploid trout are also known as 3N
or sterile trout. Triploids are infertile and thus
remove
the risk of genetic interaction with wild stocks in waters where they are
introduced for recreation purposes. Male triploids may still develop functional gonad
tissue and may participate in spawnin
g behavior, which could interfere with
reproduction of wild stock. Female triploids do not develop mature gonads and do not
exhibit spawning behavior. This reduces the potential for harmful interaction with
spawning wild fish, and increases somatic growth
and over
-
winter survival. Female
triploids in an aquaculture production system will have better flesh quality
,
for
instance
color at harvesting
,
as compared to diploids.
You can produce triploid trout by fertilizing the
normal
green trout eggs with normal
sperm and then heat shocking the eggs to induce polar body retention. Triploid fish
contain three sets of chromo
somes. One
-
half of the fish will be XXY, or triploid
males, and one
-
half will be XXX, or triploid females. Both males and females should
be ste
rile. To produce triploid fish simply fertilize the eggs with normal sperm, wait 10
minutes, and then heat shock the eggs, either at 29
°
C for 10 minutes or at 26
°
C for
20 minutes. Triploid males will probably show more gonadal development than
triploid f
emales. Gonads from a mature
triploid male may appear similar to those of a
normal fish except they will be smaller and will not produce sperm. Gonadal
development should be inhibited in triploid females. Triploid females should have
string like gonads. Go
nads of both triploid males and females can be compared to
those of normal males if they are sexed at around six months of age. All Female
Triploids are normally produced to limit any form of gonad development.
Development rates appear very similar, until
the onset of sexual maturity in All
Female/diploid trout. It is difficult to differentiate visually between triploids and
diploids, particularly when both are immature. Diploids will develop spawning
coloration, and the males develop kypes, when they matur
e whereas triploids will
maintain their non
-
mature appearance.
You might be concerned
about whether triploids are “genetically modified
organisms”. No, they are not because
no genes were introduced
at all. A genetically
modified organism (GMO) or genetica
lly engineered organism (GEO) is an organism
whose genetic material has been altered using genetic engineering techniques.
These techniques, generally known as recombinant DNA technology, use DNA
molecules from different sources, which are combined into on
e molecule to create a
new set of genes. This DNA is then transferred into an organism, giving it modified or
novel genes. Genetically modified organisms
thus
have had specific changes
introduced into their DNA by genetic engineering techniques
. These tech
niques are
much more precise than mutagenesis (mutation breeding) where an organism is
exposed to radiation or chemicals to create a non
-
specific but stable change. Other
techniques by which humans modify food organisms include selective breeding (plant
br
eeding and animal breeding).
Triploid individuals should have one
-
third more DNA
in their cells because they have three sets of chromosomes, compared with two sets
in normal diploid animals. You can buy expensive equipment that can measure the
amount of DN
A in an individual’s blood cells, but the easiest way to verify that triploid
animals have been produced is to sex them by dissection after they’re six months old
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