male/female ratio

Sheri · Sep 6, 2004

This may be a really dumb question...
and I did perform a search but I don't think I know the correct key words to get the results I am looking for...

But,

Does anyone know the ratio of male to female slings in any given clutch? Given the different life spans, I was under the impression it was not a 50/50 split.

Greg Wolfe · Sep 6, 2004

Ratio of males and females...

While I am not aware of any given ratio per eggsac, I would say, in my experience that males have the upper hand in numbers.

Immortal_sin · Sep 6, 2004

I think someone asked the question long ago, and if I remember correctly, it's a fairly even split? I may be wrong though, I often am

Bearskin10 · Sep 6, 2004

Very interesting question Sheri! I have personally never heard of there being a different ratio than 50/50 but I guess you never know? In order for this to be answered many clutches would have to be held back long enough to be sexed or at least kept track of that long, all the people that I know that breed sale most of there sac before that.

Tony · Sep 6, 2004

Yep, who raises a sac long enough to get a count...I think Sherberger presented on this topic at ATS '00.....and I think it was cambridgei and the effects of incubation temps on sex ratio.. I think it leans towards male heavy in general and 75% male on pokies...It always seems that way to me at least

T

pokiecollector · Sep 6, 2004

i heard that with pokies its 75% male and 25% female.

cichlidsman · Sep 6, 2004

Bearskin10 said:
Very interesting question Sheri! I have personally never heard of there being a different ratio than 50/50 but I guess you never know? In order for this to be answered many clutches would have to be held back long enough to be sexed or at least kept track of that long, all the people that I know that breed sale most of there sac before that.

It seems like a lot of work to get a ratio count.

Sheri · Sep 6, 2004

monantony said:
Yep, who raises a sac long enough to get a count...I think Sherberger presented on this topic at ATS '00.....and I think it was cambridgei and the effects of incubation temps on sex ratio.. I think it leans towards male heavy in general and 75% male on pokies...It always seems that way to me at least
T

Hmmmm
Maybe it can be presented again at '05 ATS? Pull some strings Tony, as you know, I will be there.

Tony · Sep 6, 2004

You can only pull strings so much, before people start complaining...I dont think Fred would want to do it again, and really who is going to go through all the trouble....Lets just say when you buy 4 subfusca babies and raise them all to happy malehood, you wonder where your 25% female is..
T

Steve Nunn · Sep 6, 2004

Due to the longevity of the female T's, there need not be as many per clutch as the males. This is researched and published info. (B.Y.Main: Dwarf males in mygalomorph spiders: adaption to envornmental hazards). This is pefectly logical given males cannot reproduce even if they make it past ultimate instar, whereas the females reproduce for many instars after the ultimate moult. Otherwise, the balance would have to be way out, it's just an adaption to suit their lifestyle and maximise offspring

Steve

Joy · Sep 6, 2004

Steve Nunn said:
Otherwise, the balance would have to be way out, it's just an adaption to suit their lifestyle and maximise offspring

Steve

Yes, but as a tarantula keeper, I think it's highly inconsiderate of them!

Joy

word · Sep 6, 2004

i'm glad our ratio is the same as theirs

Sheri · Sep 6, 2004

Joy said:
Yes, but as a tarantula keeper, I think it's highly inconsiderate of them!

Joy

LOL

thanks for that....

I'll add it to the list of other inconsiderate
things they do...

RazorRipley · Sep 16, 2004

pokiecollector said:
i heard that with pokies its 75% male and 25% female.

Genetics, like any other form of statistics/rationalizing says that in any animal, chromosomes combining give it a 50/50 shot at carrying male or female organs.

Sheri · Sep 16, 2004

RazorRipley said:
Genetics, like any other form of statistics/rationalizing says that in any animal, chromosomes combining give it a 50/50 shot at carrying male or female organs.

Yes, but maybe not so much in Tarantulas because of the difference in life span...
Hopefully, it might be covered at this year's ATS...

Tony · Sep 17, 2004

RazorRipley said:
Genetics, like any other form of statistics/rationalizing says that in any animal, chromosomes combining give it a 50/50 shot at carrying male or female organs.

I Dont know how you list genetics as a Form of statistics?
Anyway, in one particular animal (crocs) your statistical crossing is influenced alot by incubation temps, thereby slewing the results heavily beyond 50-50..
T

David_F · Sep 17, 2004

monantony said:
I Dont know how you list genetics as a Form of statistics?
Anyway, in one particular animal (crocs) your statistical crossing is influenced alot by incubation temps, thereby slewing the results heavily beyond 50-50..
T

Buuuut...since we're dealing with inverts instead of herps temp. doesn't really play a part (as far as we know). Due to my limited experience I tend to beilieve that males are a larger part of an eggsac than females. Jut seems to make more sense to me. Most likely it depends on the species though.

RazorRipley · Sep 17, 2004

monantony said:
I Dont know how you list genetics as a Form of statistics?
Anyway, in one particular animal (crocs) your statistical crossing is influenced alot by incubation temps, thereby slewing the results heavily beyond 50-50..
T

No such word as "alot"... Just something to think about :?

Rourke · Sep 17, 2004

RazorRipley said:
No such word as "alot"... Just something to think about :?

Nice, Razor! Even more useless than your first post on this thread....

First, the X-Y scenario--which prevails in humans, and with which most of us are very broadly familiar--has NOT been universally selected by evolution as a means of sex determination in animals. Tony already mentioned the well-documented temperature effect in crocodilians. It has been shown to extend to many other reptiles, and may in fact be a more commonly used determinant, over the range of the entire animal kingdom, than assortment of sex chromosome pairs during meiosis.

Additionally, even where sex depends ultimately upon which sex chromosome is present in the fertilizing gamete, there is absolutely no reason to assume that this assortment would be random. In fact, there are examples in the scientific literature which address this point explicitly, and demonstrate not only environmental effects, but also a very definite impact of genetic background.

Sheri's question is not a simple one, and certainly not an uncommon one. The bottom line is, right now, there are too many unknowns to say with a high degree of confidence what the ratio of the sexes will be from a given egg sac. Cereal box genetics will not help.

(although, I should point out, Sheri, that if you read it on the back of a box of Lefty-O's, you can pretty much bet it's true...)

Rourke

Sheri · Sep 17, 2004

Ok... so we know that the sex ratio is likely different...
But now I have been wondering, for some time now, what further differences there might be dependant on genus etc...
For instance, would arboreals, obligates, opportunistics have different ratios because of proximity issues to one another? For instance, would there need to be a higher ratio of males if females of a species were located, typically, further apart as opposed to perhaps avics, who are known to live in closer proximity to eachother, hence the idea that they are communal. (which, BTW, ALL the pet stores around here beleive)
But, I know its wishful thinking to even contemplate that we might find the answers to these questions in the next 20 years, if not longer...
So, in the words of an italian mobster, "forget about it..."

male/female ratio

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