When T's or other spiders for that matter have babies, is the ratio of males to females 50/50, or relatively close to it, like in several other species? Or are there 5 males for every female. Just curious. Tried to find the answer in a search before I posted but no luck.
Ratio of Males to females
- Thread starter Bengal21
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What animals have a 50/50 ratio?
Most animals with parents contributing x and y chromosomes have a ratio of approximately 50/50. Those numbers are based on counting in groups of 100 at the VERY least.
Reptiles may have all-male or all-female clutches based on temperature, but in mammals, the numbers stay fairly close to the 50/50.
As for Ts, one would have to keep track of the majority of the young and verify their sex. Or, one might be able to randomly sample 25 out of the clutch, and see how the numbers looked. Again, it would depend on the total number of hatchlings.
Just my input, having done a lot of equine genetic research and crunched a lot of numbers.
Marga
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Hmm.. I did not know that.
I think a study into that would be very interesting. Someone should do a sample of 15-25 slings or more if they can and do it with species from the same genus to start out with. And do that a couple times. Then they can move on and study the subfamilies. I think breeders on here could get this study done pretty well.
I think a study into that would be very interesting. Someone should do a sample of 15-25 slings or more if they can and do it with species from the same genus to start out with. And do that a couple times. Then they can move on and study the subfamilies. I think breeders on here could get this study done pretty well.
that is correct mate, L.violaceopes have a hell of alot more males than females, so if bought 2 slings, the chances are you may have 2 male's, so best to grab a girl if you can find one with these :}
In this case, I would wonder about temperature and incubation (as with some reptiles). Again, records of the temperature that the female and egg sac were kept in would be vital to determining this.
Marga
Not all animals have X and Y chromosomes. Reptiles, for example, do not. Your X/Y ratio sounds like just basic Mendellian genetics, which has limited application. Would work fairly well in equine genetics, but not in all animals.
In many animals sex is determined or at least influenced by factors other than direct genetics. Temperatures at incubation can shift male/female ratios in some animals, and some species (some fish, for example) can start life as one sex and shift to the other under certain conditions.
To come up with valid predictions in tarantulas, I think we'd need to start by directly observing tarantulas. And even then it may vary a lot according to species and conditions.
Correct, which is why I specifically said animals with parents contributing x and y USUALLY have 50/50. In chickens, the genes are opposite what you expect. Mammals traditionally have a 50/50 ratio. Reptiles do not. Insects do not - look at bees and ants. The gender of the bees is controlled by the way the larvae are raised, not only with genetic but with environmental influence.
Again, one would have to take either a completely random sampling from the egg sac (ie, keep 25 3rd instars to maturity or be able to sex the microscopic molts) or raise an entire brood and check gender. To make it valid scientifically, the female should be mated to a different male for three or more sacs, and the gender ratio of the offspring recorded.
Now, if anyone has confirmed male/female from Sac number 1234 from the pairing of So-and-so's female named Whatever, then you have the start of a study.
Marga
Even then the idealized 50/50 can be shifted. For example, I remember years ago there was speculation that the reason that in humans more males tend to be born (Not far from 50/50, but still consistently leaning toward the male side) is that the sperm carrying the Y chromosome is a tiny bit lighter than the one carrying the X chromosome and can therefore swim faster, giving a slight advantage to fertilization by male chromosomes.
Not entirely true, but it has been proven that one is faster and one longer lived... so again environmental factors (time factor of conception, temperature and Ph of the womb, etc) can effect which sperm make it where and when. Such as the old wives tale of eating bananas to produce a male... actually has some truth.
Marga
maybe im lucky 2 slings 2 females
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I've had 5 Brachypelma smithi slings, and crazy enough all five of them turned out to be female. I've always had more luck getting Brachypelma SP Female's than any other species.
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It appears I'm lucky, too- at least on B boehmei. I finally was able to get an unshredded exuvia and see the spermatheca on the biggest one I'd previously thought was male. 
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Lorum
Arachnosquire
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A friend of mine had 3 spiderlings of Lampropelma violaceopes, and we now know that two of them are males and one is a female.
I bought myself two spiderlings of the same species (with another dealer), and I now have one male and one female.
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I think the only way to make a conclusion as to the ratio of males to females would to take an entire egg sac, raise them up and sex them all. If you took 50 out of a 100 eggs you could very well take 50 males and leave 50 females. (that is if its 50/50) IMO thats the only correct way to find out the ratio.
I brought up the temperature vs male/female ratio and i believe Schoolman volenteered to do an experiment. Raising a sac at room temp and one at elevated temps.
I brought up the temperature vs male/female ratio and i believe Schoolman volenteered to do an experiment. Raising a sac at room temp and one at elevated temps.