The elusive homozygous spider...?

[Chris Rossi]

I bred a spider x spider and got this somehow.

http://www.spiderman-3-trailer.com/spiderman_6.jpg

[RandyRemington]

Well, the reason I think it is more likely that homozygous spiders exist than that homozygous spider is lethal is because I've heard credible rumors of the first, and nothing but speculation of the 2nd. There is a member on this forum who claims to own a spider that has only been bred a fairly limited number of times, but so far has produced 100% spider offspring. I have absolutely no reason to doubt that claim. I've also heard 2nd or 3rd hand of some others who have been bred quite a bit more and still throw 100% spiders. Now, I realize this proves nothing, which is why I said I believe this possibility over the other one, rather than saying this is a fact.

It would be an easy enough thing to get pretty convincing proof if either one big breeder or a group of smaller breeders would pair known het spider to known het spider (or spider combos would work as well of course), and document the offspring ratios. 3/4 spider means it is non-lethal dominant with no visible homozygous form, 2/3 spider means it is co-dominant with a lethal homozygous form.

The nature of the problem of proving a mutation homozygous lethal is that it's much harder to produce credible evidence of something not existing than that it might exist.

I'll have to find and re-read the evidence from the keeper here. I didn't doubt at all that the info was accurate; my only question was if it was enough to be very significant. I remember when I first read it just didn't seem like enough spiders in a row. I also remember there where a lot of dead eggs which should be randomly distributed between spiders and non spider offspring so really shouldn't matter but it did make me wonder if somehow the dead eggs tainted even the streak of spiders that was presented. It would have also been nice to know if that male spider even had the chance to be homozygous by having both spider parents. Hopefully that male will be able to produce some more full term eggs this year.

I think I've only heard detailed results from a single spider x spider breeding so too small to be significant that 1/4 of the eggs where undersized and didn't hatch.

[ctrlfreq]

Is it just me, or have they been around long enough that the probability is that there isn't an homozygous spider?

The real issue is the absence of a BP genome map and the genetic tests such a map would allow for. Since there is no documented super form, it's assumed the homozygous and heterozygous forms are visually identical, and thus, a particular animal can only be suspected of being homozygous.

While you can suspect an animal bearing a dominant trait of being homozygous, the only "proving" you can do is when it's shown to be heterozygous by throwing even a single non-spider offspring.

[Mike Schultz]

While you can suspect an animal bearing a dominant trait of being homozygous, the only "proving" you can do is when it's shown to be heterozygous by throwing even a single non-spider offspring.

I've heard of albino x albino pairings producing normal offspring before though :shrug:

[GenePirate]

3/4 spider means it is non-lethal dominant with no visible homozygous form, 2/3 spider means it is co-dominant with a lethal homozygous form.

To get some preliminary data for a study, it would be a good idea to conduct a poll, either online or by querying reputable breeders. The question would be something like: "Not counting slugs or dead eggs, what were the spider ratios in every clutch ever produced from two parents each carrying the spider mutation?"

1) Data should be compiled from trusted breeders who keep meticulous records. 2) There must be enough data to compile a statistically significant sample population. 3) Unfortunately, slugs/bad eggs can not be counted because the genetics of the dead embryos are unknown, and unfertilized eggs can't count. It would be helpful to know, however, if the 2/3 ratio clutches also produce an overwhelming number of dead eggs. So, although they can't be counted, they might help support a conclusion in a large population study.

Regardless of whether the breeder was breeding... spider x spider... or spider desert ghost woma x spider woma axanthic, the other genes do not have to be revealed, so "secret" crosses can be protected. However, this may affect the data if other combinations prove to produce lethalities. So, double woma crosses obviously must be left out.

If any herp folks out there think this type of study would be worthwhile, please post your ideas, suggestions, caveats, etc. And, if there's a stats guru out there, wanna volunteer your expertise?

[Ben Biscy]

I've done a lot of thinking on this one recently, and will probably be producing a homozygous spider line (long term goal) to see what comes from it.

my thoughts are a dominant trait that is passed on easily to offspring has been bred so because of how easy it is to produce more of the same morph. wanna make spiders? get a spider and a normal, problem solved.....

too many people out there like to take the cheap route. many are much more particular, but also much more reclusive. i'm sure there will be more on this in the next few years.

[Raven86]

I'm fairly new to ball python genetics and I believe it's safe to say it far more complicated than I expected lol!

Anyway, on the topic of homozygous spiders... I've played around with just percentage points on potential genetic outcomes and can never seem to get more than a 25% overall chance of producing any spider morph that is homozygous. Granted this 25% is theoretical and simply on paper things seem to change a fair bit in real life practice though. I have however found a coupling that produces potential for many awesome spiders if it worked. If I had 2 mahogany cinnabees you even have chances of homozygous super cinnamon spiders. I'd like to see that since super cinnamon is solid black and I'm not certain what spider would do to that.

I've torn through many different pairings but this seems to be one of my favorites as far as high variance in offspring.

[Eric Alan]

I'm fairly new to ball python genetics and I believe it's safe to say it far more complicated than I expected lol!

Anyway, on the topic of homozygous spiders... I've played around with just percentage points on potential genetic outcomes and can never seem to get more than a 25% overall chance of producing any spider morph that is homozygous. Granted this 25% is theoretical and simply on paper things seem to change a fair bit in real life practice though. I have however found a coupling that produces potential for many awesome spiders if it worked. If I had 2 mahogany cinnabees you even have chances of homozygous super cinnamon spiders. I'd like to see that since super cinnamon is solid black and I'm not certain what spider would do to that.

I've torn through many different pairings but this seems to be one of my favorites as far as high variance in offspring.

And for your first trick (and first post), you will bring a 3.5 year old thread back to life! Much discussion has been done since then - still no such thing as a homozygous spider. No concrete reason why, but there are many theories.

[MasonC2K]

I'm fairly new to ball python genetics and I believe it's safe to say it far more complicated than I expected lol!

Anyway, on the topic of homozygous spiders... I've played around with just percentage points on potential genetic outcomes and can never seem to get more than a 25% overall chance of producing any spider morph that is homozygous. Granted this 25% is theoretical and simply on paper things seem to change a fair bit in real life practice though. I have however found a coupling that produces potential for many awesome spiders if it worked. If I had 2 mahogany cinnabees you even have chances of homozygous super cinnamon spiders. I'd like to see that since super cinnamon is solid black and I'm not certain what spider would do to that.

I've torn through many different pairings but this seems to be one of my favorites as far as high variance in offspring.

I hereby anoint thee Thread Necromancer!

[tjohn310]

And for your first trick (and first post), you will bring a 3.5 year old thread back to life! Much discussion has been done since then - still no such thing as a homozygous spider. No concrete reason why, but there are many theories.

I think that the person with the "dominant" spider should breed the babies back to it, even though it's in-breeding and incest, but it will also help determine the answers. Don't know whether that particular ball python is left but the thing is that most of these spiders have a genetic head wobble and we don't have the answers to that yet either. The spider morph is beautiful alone and is great for creativity and it would be great if we knew more about them so its actually a great thing that Raven86 has re-sparked this conversation.