We are having a debate about the term Pure. Please have your say.

[Disciple]

Ok people time to make history we will start with a simple one for this we just need a yes or no answer we will define the term pure as it will relate to shrimp this is only single gene line shrimp no hybrids ie tibee, pinto, misch etc. Going forward in our hobby pure in reference to shrimp will mean the following any shrimp that produces and has produce all offspring of the same genetic make up as the parents for 3 or more generations shall be deemed pure.

These are some interesting responses that we have had.

1. Yes! But I'm not okay with just 3 generations to call it pure. As I told earlier in another discussion, I've been getting only crs offspring in my crs only tank for the past 2 years until now(2 golden bees after more than 10+ generations approx, meantime no new shrimps were added in the past 1.5 years)

2. Perhaps the term "true-breeding" (or pure-breeding) is more useful than pure, most if not all these things are hybrids after all. There are no wild species that correspond to a Taiwan/Shadow bee, for example. The true breeding stability comes from dilligent selection and line breeding for a given trait until no other traits occur. That's the hard part of the work and down to the quality of the breeder.

3. Well pure means pure, not 80<90 %.

[fishmosy]

Yes from me.

[dash77]

No from me

[OzShrimp]

confused about what you are asking for a yes or no answer and 3 options ? 

[jayc]

I think the question is ...

"any shrimp that produces and has produce all offspring of the same genetic make up as the parents for 3 or more generations shall be deemed pure."

 

3 generations is not enough to deem any shrimp as pure if it has any mixed gene.

Take this article I wrote about genes for example. http://shrimpkeepersforum.com/forum/topic/7637-tibee-taitibee-pinto-mischling-f1-f2-terms-explained/?do=findComment&comment=93580

All it takes is for 2 shrimps carrying the recessive gene in the F2 or F3 generation to produce an unwanted gene.

The fact that you might not see it for several generations (or years) is just down to odds/chance of the shrimps carrying recessive genes mating.

Once a pure shrimp is mixed and carries genes of another type of shrimp( eg PRL with golden bee genes), then it will take many, many generations of breeding, and culling golden genes out before you would even consider it pure again. 

The fact that it might breed True for many generations, just means that the odds are high for the dominant gene.

The fact that it might breed True for many generations, also does not mean it is Pure. Cause, as I mentioned, it just takes that slim chance of two PRL recessive carriers of golden genes to spit out a Golden bee. And a Golden bee is not a PRL.

 

Edited September 19, 2015 by jayc

[OzShrimp]

ohwell i agree 3 generations is not enough !

[fishmosy]

I think the question is ...

"any shrimp that produces and has produce all offspring of the same genetic make up as the parents for 3 or more generations shall be deemed pure."

 

3 generations is not enough to deem any shrimp as pure if it has any mixed gene.

Take this article I wrote about genes for example. http://shrimpkeepersforum.com/forum/topic/7637-tibee-taitibee-pinto-mischling-f1-f2-terms-explained/?do=findComment&comment=93580

All it takes is for 2 shrimps carrying the recessive gene in the F2 or F3 generation to produce an unwanted gene.

The fact that you might not see it for several generations (or years) is just down to odds/chance of the shrimps carrying recessive genes mating.

Once a pure shrimp is mixed and carries genes of another type of shrimp( eg PRL with golden bee genes), then it will take many, many generations of breeding, and culling golden genes out before you would even consider it pure again. 

The fact that it might breed True for many generations, just means that the odds are high for the dominant gene.

The fact that it might breed True for many generations, also does not mean it is Pure. Cause, as I mentioned, it just takes that slim chance of two PRL recessive carriers of golden genes to spit out a Golden bee. And a Golden bee is not a PRL.

 

So if I'm reading this right, and based on my limited knowledge of Mendelian genetics, recessive genes should definitely appear as a phenotype (i.e. affect the morphology or look of a shrimp) within three generations in at least 1/4,1/8 or 1/16 of the offspring depending on the number of generations, ect. Based on my interpretation of the definition of pure in the OP, the colony could no longer be called pure if ANY offspring showed up within three generations that were not the intended variant. If such offspring did show up, the count would need to start again. Hence any variant that has a hybrid lineage would take many, many generations to breed pure, if not ever. As suggested in another thread, a better name for these hybrid variants that breed true (or close to 100% true) would be "line bred".  

Hence I read the OP as CRS, CBS, cherry variants and other non-hybrid shrimp are the only shrimp that can ever be considered "pure" which is fair enough. That said, a hybrid variant that produces close to 100% offspring that are the same variant deserves recognition because this takes a lot of work on behalf of the shrimpkeeper - once again I think the term "line bred" is fitting.

 

[jayc]

Top of the class on mendelian genetics.  

The likelihood of the recessive phenotype appearing is reduced after 3 but it's never completely eliminated. 

[Baccus]

From memory I think they deem 7 generations before a cross bred line becomes pure again. But I suspect that somewhere deep in the genetics there will be some residual of the original cross.

[fishmosy]

Here is a can of worms - I've based my thoughts on Mendelian genetics. What if shrimp genetics dont conform to Mendelian genetics?

[Jo]

I agree that 3 generations isn't enough to determine purity.

However, I also think that the term is of limited use anyway because when buying shrimp you're relying on un-observable information provided by a 3rd party.