Question about spider to spider breeding

[dr del]

Hi,

I was reading a thread which once again mentioned the possibility of the homozygous spider being fatal early in the development.

Have any of you bred spider to spider and been in the habit of palpating to count follicles?

I just wondered if that would be the most reliable way to see if the percentage of any slugs or normal looking but infertile matched what would be similar to the expected homozygous percentage?

I was basing this on the simplistic idea that any homozygous complications could only happen at or after ovulation and the count before then is a relatively good indication of the potential number of offspring.

Does that make any sense at all?


dr del

[wolfy-hound]

I'm not sure how you'd prove that a offspring that never hatched was homozygous for spider.
Unless you're doing genetic testing, and can tell the spider gene apart, how would you know it had a double dose of spider?

[dr del]

Hi,

You wouldn't even try to prove the slugs were double dose spiders.

But if you expected 25% of the resultant eggs to be homozygous if measured over a large enough sample and ( once a statistical average of slugs derived from a non-spider control group had been removed from the numbers you saw ) you were seeing a 25% larger than expected number of slugs or failed hatchings it would definately suggest that there were indeed developmental complications.

I am not very good at explaing this so will try a couple of examples.

.....................Total # of eggs........# of slugs.......# failed to hatch....# ok

Control group......100...................5.......................5................90

a)Spider x Spider.100...................23......................5................72

b)Spider x Spider.100....................5.......................23..............72

c)Spider x Spider.100....................5.......................5...............90


Now that is obviously simplistic but it hints (but only hints ) the following according to group;

a) There is a problem with homozygous spiders and it occurs very early in development.

b) There is a problem with homozygous spiders but it happens much later in the development of the hatchling.

c) There is no problems with homozygous spiders developing.



dr del

[West Coast Jungle]

There have been claims of double spiders and if this being true its seems to me it would be easier to breed the animal, preferably a male, to several female normals and you should see nothing but spiders.

The other thing to do is breed spider to spider and hold back several males and breed them to non spider females and see if one throws out all spiders.

I think so many factors play into slugs so to say it was spider related would be hard to do with any certainty.

[MarkS]

I think I see what you mean. If someone could get an accurate reading on the number of follicles produced by a female spider before ovulation, then compared it to the number of live young hatched after breeding to a male spider you could figure out what percentage if any of offspring that you're missing out on.

It's an interesting idea, but it would probably have to be done by someone with an ultrasound machine to get a completely accurate reading. I know my hands just aren't sensitive enough (nor are my females cooperative enough) to always be able to get an accurate reading on the number of follicles produced by any given female.

[RandyRemington]

There have been claims of double spiders and if this being true its seems to me it would be easier to breed the animal, preferably a male, to several female normals and you should see nothing but spiders.

The other thing to do is breed spider to spider and hold back several males and breed them to non spider females and see if one throws out all spiders.

I think so many factors play into slugs so to say it was spider related would be hard to do with any certainty.

But you have to wonder why 20 years after the founding spider sold no one has come forward with a homozygous spider. It could just be that people are much more interested in using their female spiders for combos and not enough homozygous spiders have been produced for one to get in the hands of someone who would keep records to prove it and report the results. But if spider is homozygous lethal then we will never see a proven one and dr del's statistical method of counting disappearing follicles, slugs, or egg deaths will be as close as we can come to proof depending on how early the homozygous spider genotype is fatal.

[kc261]

Another possibility is to simply count the numbers of live, healthy offspring of spider x spider pairings.

If, after a large enough sample to be statistically relevant, about 3/4 (or higher) of the offspring are spiders, then that would indicate that homozygous spider is just fine.

On the other hand, if only about 2/3 are spiders, that would indicate that the homozygous are dying before they hatch (either as slugs, or perhaps reabsorbed and never even laid).

No ultrasound necessary.

When I first was thinking about this, I thought the possibility of some spiders being bred to get the stats being homo would be an issue because it would throw off the expected ratios. However, it would raise the expected # of spider offspring to even higher than 3/4, so it still would not really be confused with the lower 2/3 number.

[Fearless]

But you have to wonder why 20 years after the founding spider sold no one has come forward with a homozygous spider. It could just be that people are much more interested in using their female spiders for combos and not enough homozygous spiders have been produced for one to get in the hands of someone who would keep records to prove it and report the results. But if spider is homozygous lethal then we will never see a proven one and dr del's statistical method of counting disappearing follicles, slugs, or egg deaths will be as close as we can come to proof depending on how early the homozygous spider genotype is fatal.

Correct me if im wrong but the eggs are never fertilized til after ovulation (hence releasing the egg) so the homozygous genotype wouldn't be a factor til well after the follicle counting is done.

But lets say for example I had something like happened to me just a few weeks ago. I palpated six follicles, like 100 % sure there were six and come time to lay there was five eggs, no slugs. What happened to number six? Is this possible that it just did not get fertilized and she deficated it out? Or would one suspect there are fraternal twins in one of the eggs? Or is it just possible that a female can reabsorb the follicle within about a week of ovulation? And if thats possible then that kinda pisses away the idea of counting follicles to be able to get a controlled number of possible fatal homozygous spiders vs just females that for some uncontrolled reason absorbs them.

[Fearless]

Another possibility is to simply count the numbers of live, healthy offspring of spider x spider pairings.

If, after a large enough sample to be statistically relevant, about 3/4 (or higher) of the offspring are spiders, then that would indicate that homozygous spider is just fine.

On the other hand, if only about 2/3 are spiders, that would indicate that the homozygous are dying before they hatch (either as slugs, or perhaps reabsorbed and never even laid).

No ultrasound necessary.

When I first was thinking about this, I thought the possibility of some spiders being bred to get the stats being homo would be an issue because it would throw off the expected ratios. However, it would raise the expected # of spider offspring to even higher than 3/4, so it still would not really be confused with the lower 2/3 number.

The problem with that is its just odds and to be able to have a well educated guess with that the control number would need to be probably in the thousands.

[GenePirate]

Another possibility is to simply count the numbers of live, healthy offspring of spider x spider pairings.

If, after a large enough sample to be statistically relevant, about 3/4 (or higher) of the offspring are spiders, then that would indicate that homozygous spider is just fine.

On the other hand, if only about 2/3 are spiders, that would indicate that the homozygous are dying before they hatch (either as slugs, or perhaps reabsorbed and never even laid).


When I first was thinking about this, I thought the possibility of some spiders being bred to get the stats being homo would be an issue because it would throw off the expected ratios. However, it would raise the expected # of spider offspring to even higher than 3/4, so it still would not really be confused with the lower 2/3 number.

Yeah, Casey, (and Dr. Del) I contacted one or two of the biggest spider breeders to ask for clutch records from spider x spider pairings (including bumble bees x lesser bees, etc.), but I haven't heard back. This would be a quick and dirty way to gather preliminary data. I've got a stats program that would calculate the number of samples required to do a statistically significant study. If the p value is acceptable, it would give you a good idea whether or not the mutation was indeed lethal.