Self cloning "blue" crayfish?

[ScatMan]

Not really. They are identical at a genetic level. The ones in my tank are exactly the same as the original ones found in that german pet store back in the 90's. That is what makes them so unique as a species. There are really only a handfull of creatures on the planet (that we know about) that reproduce via parthenogenesis.

Environmental variables can cause differences though. If one gets more food than another, it will grow faster. Assuming color is partly based on food, and 1 cray eats more of a type of food that promotes blue than another, that cray will show more blue. If one cray is attacked by a fish as a juvenile, it might show a greater distrust of fish than it's siblings. It might spend more time hiding.

If some guy decides to split them up and stick them all in jars with different water hardness, they might each show a different color.

You see the same kind of thing in Identical Twins in humans. They can't both experience exactly the same things at exactly the same times in their development, so their personalities can be very different. Genetically they are identical though.

REALLY, there really is genetic variation, even between individuals. the mechanism that duplicates dna is not perfect and often makes tiny mistakes. over time, those tiny mistakes can add up into significant variation.

there are tons of asexual organisms, most are primitive like bacteria but there are more advanced organisms too like plants, quite a few insects, marmokrebs and even komodo dragons (and many many more)! now komodos normally reproduce sexually BUT it has been proven that they can reproduce asexually as well and when they do, all the offspring are male (pretty interesting stuff)!!!

if you don't believe it, do a little googling.

 

[Dark Jester]

Ok, here's a quote from the Wiki on Parthenogenesis:

""Marmorkrebs" are parthenogenetic crayfish that were discovered in the pet trade in the 1990s.[11] Offspring are genetically identical to the parent, indicating it reproduces by apomixis, i.e. parthenogenesis in which the eggs did not undergo meiosis.[12]"

From the Wiki on Marmokrebs:

"Model organism
Marmorkrebs are the only known decapod crustaceans to reproduce by parthenogenesis.[1] All individuals are female, and the offspring are genetically identical to the parent.[5] Because Marmorkrebs are genetically identical, easy to care for,[6] and reproduce at high rates, they are a potential model organism, particularly for studying development.[7] A major drawback, however, is the long generation time (several months) compared to other research organisms.[8]"

Still want to argue that they are not genetically identical? Since the eggs do not undergo Meiosis, the process by which 2 sets of parent DNA are merged to promote genetic variation, all of them are 100% identical. The only variation you will see is produced by environmental variables, as I stated previously.

Also if you read that page, there really aren't a ton of animals out there that do it. Outside of bacteria you're probably looking at less than 50 examples from across the Insect, Crustacean, Snail/Flatworm, Reptile, Shark, Bird, and Mammal groups. Out of the tens or hundreds of thousands of species on this planet, I would hardly call that a ton.

 

[ScatMan]

Ok, here's a quote from the Wiki on Parthenogenesis:

""Marmorkrebs" are parthenogenetic crayfish that were discovered in the pet trade in the 1990s.[11] Offspring are genetically identical to the parent, indicating it reproduces by apomixis, i.e. parthenogenesis in which the eggs did not undergo meiosis.[12]"

From the Wiki on Marmokrebs:

"Model organism
Marmorkrebs are the only known decapod crustaceans to reproduce by parthenogenesis.[1] All individuals are female, and the offspring are genetically identical to the parent.[5] Because Marmorkrebs are genetically identical, easy to care for,[6] and reproduce at high rates, they are a potential model organism, particularly for studying development.[7] A major drawback, however, is the long generation time (several months) compared to other research organisms.[8]"

Still want to argue that they are not genetically identical? Since the eggs do not undergo Meiosis, the process by which 2 sets of parent DNA are merged to promote genetic variation, all of them are 100% identical. The only variation you will see is produced by environmental variables, as I stated previously.

Also if you read that page, there really aren't a ton of animals out there that do it. Outside of bacteria you're probably looking at less than 50 examples from across the Insect, Crustacean, Snail/Flatworm, Reptile, Shark, Bird, and Mammal groups. Out of the tens or hundreds of thousands of species on this planet, I would hardly call that a ton.

"the process by which 2 sets of parent DNA are merged to promote genetic variation"
^this is not the only factor that causes genetic variation. radiation from sunlight, chemicals and random copying errors all change dna. it's simply wrong to state that they are identical.

the animals are not 100% genetically identical. they say "identical" for all intents and purposes, but it doesn't mean 100%. it's a reflection of the way that they test for genetic similarity with "short tandem repeats" instead of actually looking at every base on the whole strand of dna.

while there are relatively few organisms (and there are more than the 50 listed on wiki) that asexually reproduce, i would hesitate to call it rare.

 

[Dark Jester]

"the process by which 2 sets of parent DNA are merged to promote genetic variation"
^this is not the only factor that causes genetic variation. radiation from sunlight, chemicals and random copying errors all change dna.

Considering radiation from sunlight, and chemicals would be external environmental factors, I think you are proving my point.

Another quote from the Parthenogenisis wiki:

"A litter of offspring resulting from parthenogenesis may contain genetically identical siblings. In organisms possessing an XY chromosome system, parthenogenic offspring are always female, but they are not necessarily genetically identical to one another or to their mother (some chromosome segments may differ because of meiosis)."

That would be what you are referring to by 'random copying errors'. However, the statement at the end is what causes the variation: "some chromosome segments may differ because of meiosis"

Marmokreb embryos do not undergo meiosis. They are thought to reproduce via apomixis. The subjects tested really, seriously, truely do not show genetic variation. Tests have shown that all marmokrebs are 100% genetic clones.

Do you have any links to sources stating that these random copying errors exist in Marmokrebs? I'm sure there are some laboratories and universities that would be interested in those results. I would personally be interested as well, since I have not located anything stating such in my exhaustive search across the internet about these guys.

However, I have read a couple papers about them really being genetic clones. Take a look at this paper: http://www.springerlink.com/content/9276u270122046n8/

Quote from abstract: "Based on its exclusively parthenogenetic reproduction mode, it has been suggested that the Marmorkrebs (Crustacea, Decapoda, Astacida), a recently discovered crayfish, is an excellent candidate for research addressing the aforementioned questions. However, until now, a study using molecular markers that clearly proves the genetic uniformity of the offspring has been lacking. Here, with this first molecular study, we show that this crayfish indeed produces genetically uniform clones. We tested this with 19 related individuals of various generations of a Marmorkrebs population by means of six different microsatellite markers. We found that all examined specimens were identical in their allelic composition. Furthermore, half of the analyzed loci were heterozygous. These results and the absence of meioses in previous histological studies of the ovaries lead us to conclude the Marmorkrebs propagates apomictically. Thus, a genetically uniform organism with complex morphology, development, and behavior is now available for various laboratory studies."

This is the reason they are being looked into for study in developmental biology. They all start out identical, and environmental variables cause change. Essentially it's the same as the experiment I proposed above. Take a bunch of identical offspring and subject them to differing water hardness to observe possible visible changes in color.

Think I'm done on this topic until a research paper shows up stating that a genetic variation has been located.

 

[ScatMan]

Considering radiation from sunlight, and chemicals would be external environmental factors, I think you are proving my point.

i believe your point was that they don't genetically mutate and are 100% genetically similar. my point is that this is not true.

Another quote from the Parthenogenisis wiki:

"A litter of offspring resulting from parthenogenesis may contain genetically identical siblings. In organisms possessing an XY chromosome system, parthenogenic offspring are always female, but they are not necessarily genetically identical to one another or to their mother (some chromosome segments may differ because of meiosis)."

That would be what you are referring to by 'random copying errors'. However, the statement at the end is what causes the variation: "some chromosome segments may differ because of meiosis"

no, meiosis is one possible cause of genetic variation.

what i mean by random copying errors is; dna is split in half by a protein, then another protein matches the bases on the one half of the dna with other bases floating around in the cell until it puts the dna back together and this is where the errors occur because it is not a perfect process. this is one way in which organisms evolve, and is common knowledge with scientist which is why it's not specifically stated, as it is implied.

Marmokreb embryos do not undergo meiosis. They are thought to reproduce via apomixis. The subjects tested really, seriously, truely do not show genetic variation. Tests have shown that all marmokrebs are 100% genetic clones.

they're not 100% genetically identical, this is where you are mistaken (see further down this post where i show you why you are mistaken). meiosis is not the only way to change dna.

Do you have any links to sources stating that these random copying errors exist in Marmokrebs?

marmokrebs specifically, no. it applies across all organisms though.
http://evolution.berkeley.edu/evosite/evo101/IIIC1aRandom.shtml

I'm sure there are some laboratories and universities that would be interested in those results. I would personally be interested as well, since I have not located anything stating such in my exhaustive search across the internet about these guys.

However, I have read a couple papers about them really being genetic clones. Take a look at this paper: http://www.springerlink.com/content/9276u270122046n8/

Quote from abstract: "Based on its exclusively parthenogenetic reproduction mode, it has been suggested that the Marmorkrebs (Crustacea, Decapoda, Astacida), a recently discovered crayfish, is an excellent candidate for research addressing the aforementioned questions. However, until now, a study using molecular markers that clearly proves the genetic uniformity of the offspring has been lacking. Here, with this first molecular study, we show that this crayfish indeed produces genetically uniform clones. We tested this with 19 related individuals of various generations of a Marmorkrebs population by means of six different microsatellite markers. We found that all examined specimens were identical in their allelic composition. Furthermore, half of the analyzed loci were heterozygous. These results and the absence of meioses in previous histological studies of the ovaries lead us to conclude the Marmorkrebs propagates apomictically. Thus, a genetically uniform organism with complex morphology, development, and behavior is now available for various laboratory studies."

"allele" google it, it's a short sequence of dna used to identify individuals and determine relatedness. it is not anywhere near the whole dna sequence. just because 2 orginisms have the same alleles does not mean they are 100% genetically identical.

This is the reason they are being looked into for study in developmental biology. They all start out identical, and environmental variables cause change. Essentially it's the same as the experiment I proposed above. Take a bunch of identical offspring and subject them to differing water hardness to observe possible visible changes in color.

Think I'm done on this topic until a research paper shows up stating that a genetic variation has been located.

i'm sorry you don't understand the genetic processes of evolution enough.

 

[ScatMan]

The Causes of Mutations
http://evolution.berkeley.edu/evosite/evo101/IIIC3Causes.shtml

 

[Dark Jester]

So wait, you're counting on the possibility of a random genetic mutation happening, not only happening but one that does have the ability to be passed on to offspring, and using that as basis for stating that they are certianly not currently identical?

Quite a bit of random there for you to be so certian. Any specific case studies you can provide of genetic mutations being passed down among creatures that reproduce apomictically?

i'm sorry you don't understand the genetic processes of evolution enough.

Maybe not yet, but I'm an extremely fast study. I'll probably be able to pass a first term genetics college exam by tomorrow morning. We'll see how well your theories hold up.

 

[knifegill]

I think what we have here is a differing opinion of how stable the transcription process really is. One is saying the genetic pattern is fragile and easily mutated. The other is of the impression that such mutations are uncommon at best and that marbled crays do not deviate in any way unless a catastrophic environmental factor is involved. Amirite?

 

[Dark Jester]

Pretty much. Way to simplify it!

I don't deny the instability of DNA in species that reproduce via other methods. I question the possibility of occurrance in a species that is proven to only reproduce apomictically.

Edit: Perhaps I should amend my stance to state that they are 100% identical, with the possibility to go 99.9999999% identical if some environmental factor causes a change in the dna capable of being passed on to offspring?

 

[ScatMan]

So wait, you're counting on the possibility of a random genetic mutation happening, not only happening but one that does have the ability to be passed on to offspring, and using that as basis for stating that they are certianly not currently identical?.

it's more than a possibility, it's almost a certainty that some of the billions of base pairs will be changed during the process of dna duplicating itself.

Quite a bit of random there for you to be so certian. Any specific case studies you can provide of genetic mutations being passed down among creatures that reproduce apomictically?

look around man, i can't do all your homework. dna is not perfectly stable.

if you believe in evolution, you believe that we all started out as asexual single celled organisms right? well, how do we go from there to here? answer, genetic mutation in an asexual organism.

Maybe not yet, but I'm an extremely fast study. I'll probably be able to pass a first term genetics college exam by tomorrow morning. We'll see how well your theories hold up.

they're not my theories, they're scientific fact.