MTF
>This is just a though, but is it possible that ph triggers a mechanism
>such as a lethal
>gene etc., that causes either male or female eggs to not even hatch and
>therefore skew the
>sex ratio?
>
>Bjorn
>
>Who is up too late and is probably spouting nonsense ;)
>
>Bruce Hansen wrote:
>
>> This is probably the 64000 $ question - IMO the egg comes first, then the
>> sperm and determines the genetic sex of the embryo. Perhaps during the
>> process of development within the egg of that embryo external factors
>> especially temperature can affect the hormonal and other chemical signals
>> that are programmed into the genetic code for that individual so that
>> differentiation into male or female will be either enhanced or obstructed
>> or even unmodified. The end result is as observed in sex ratios in the
>> offspring.
>>
>> The trick is to find out the critical temperatures (for each species
>> probably). In nature this is probably ironed out by some variability in
>> temperatures for fry produced in smaller and larger bodies of water as well
>> as early and late in the season. In the circumstances of artificial raising
>> and trying to initiate a more desirable sex ratio in fry the evidence so
>> far seems perhaps in favour of lower temps influencing more females but it
>> also appears that we need more accurate info on what actual temperatures
>> our eggs are being incubated at before we have a starting point for
>> manipulation. It sounds too painstaking and persistent for me :-(
>>
>> Regards,
>> Bruce.
>>
>> Bruce Hansen, ANGFA, caring for our aquatic ecosystems.
>>
>> Please visit us at http://www.ozemail.com.au/~fisher/angfa.htm
>>
>> ----------
>> > From: Adrian R. Tappin <atappin at ecn.net.au>
>> > To: rainbowfish at pcug.org.au
>> > Subject: Re: [RML] sex reversal was Male or Female Kubutu Rainbowfishes
>> > Date: Friday, 20 March 1998 8:05
>> >
>> > At 00:01 19/03/98 -0700, Julie wrote:
>> >
>> > >snip,snip.
>> >
>> > >Hope this helps some. You may also want to know that I do not usually
>> pull
>> > >out the lunkers, so some of the difference *may* be due to cannibalism
>> by
>> > >the larger, faster growing ones (males?) on the runts (females??). Just
>> a
>> > >thought. I have a sm batch of 6 now and they are beginning to look like
>> > >mostly gals, but are still small yet.
>> >
>> > Personally, I think its probably temperature influenced as Gary
>> mentioned. I
>> > was reading an aquacultural article (still in press) and it mentioned
>> > temperature "in passing" but didn't go into details.
>> >
>> > some extracts:
>> >
>> > "Sex reversal is the manipulation of the fish either with the use of
>> > hormones or temperature to drive a population towards being completely
>> one sex"
>> >
>> > "The sex of an animal is determined by one of two methods:
>> > 1.Sex determination occurs at the time of fertilisation, when the
>> > chromosomes from the male and the female join forming a zygote.
>> >
>> > 2.Sex differentiation occurs as the larvae is developing and there are
>> > bundles of cells in its body that become various organs. The
>> differentiation
>> > into either male or female occurs as a group of cells are developing into
>> > gonads."
>> >
>> > Does anyone know when the sex of rainbowfishes is determined.
>> >
>> > And I don't want any funny answers Bruce! - although 'tongue in cheek'
>> > answers would be alright ;-)
>> >
>> > Adrian.
>> >
>> >
>> >
>> >
>> >
>>...............................................................
>> > Adrian R. Tappin
>> > "Home of the Rainbowfish"
>> > http://www.ecn.net.au/~atappin/home.htm
>> >
>>...............................................................
>> >
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