Reptile & Amphibian Forums

I'm reposting this cuz i didn't get any info the last time i post this and i'm sure lots of people are still curious.

What is the relationship btwn incubation temperatures and the sex of hatchlings? I read a long time ago that the sex of baby turtles, alligators and other reptiles is determined by the temperature the eggs are kept. so how does this relate to Colubrids? has any research been done on this... the reason i ask is because of the sex ratios we see in Kings and Milks... some may produce an entire clutch of females or males, or high male low female or hi female low male while others have an even distribution so why is that??

Exert i just found:
Although the exact mechanism by which temperature determines sex is not
known, it appears that temperature determines whether the embryo develops
testes (becomes male) or ovaries (female). Early embryos have indifferent
gonads capable of becoming either testes or overies. In many turtle
species, higher incubation temperatures turn the early gonads into ovaries,
resulting in females, while lower temperatures turn the gonad into testes,
resulting in males. The reverse is true in alligators, where higher
temperatures yield males and lower, females. In mammals, the same process
occurs, but is regulated by genes rather than temperature: a particular
gene called the testis determination factor on the Y chromosome transforms
the early gonads into testes in males. Females, with 2 X chromosomes,
don't have the gene so ovaries develop.

One way in which temperature might affect the development of the gonad is
by regulating steroid hormone production. For instance, if turtle eggs are
incubated at high, female-producing temperatures but treated with the male
steroid testosterone, males will develop. Or, if eggs at low,
male-producing temperatures are treated with the female steroid hormone
estrogen, females develop instead. All steroid hormones are synthesized
from the cholesterol molecule, and share common features in their synthetic
pathway. Testosterone can be converted to estrogen by the enzyme
aromatase, for instance. So it is possible that in reptiles, certain
enzymes involved in the synthesis of estrogen and testosterone are
temperature-sensitive.

Louise Freeman

Mary Baldwin College

Source: An Introduction to Behavioral Endocrinology, by R. J. Nelson
(2000) pp. 122-124

Here are additional question which came up:

Posted by: crimsonking at Mon Sep 19 20:48:30 2005 [ Report Abuse ] [ Email Message ]

..or at least qualify it a bit..
(Speaking of colubrid snakes here)
Is the temperature at a certain time during incubation a deciding factor??
I would assume yes, but I have no clue really.
During the say..60 days it takes to incubate some colubrid eggs, would a "spike" in temps at the first/mid/last 20 days for a set duration have an effect??
I think some would think a prolonged "spike" in temps generally has a negative (early hatch, kinks, etc) but what about a shorter one? And is it more/less a difference at a certain time during the incubation period?
I wonder if most deformed (visually) snakes are one sex or the other.
Obviously, there is a lot to be discovered and I for one have let opportunities go by when things like this have happened to me by not documenting much more info.
I really have only questions...
I would also assume (possibly quite erroneously) that snakes tend to nest and lay in spots where temps do not fluctuate wildly or stay too hot or cold either for extended periods.(FR??)
In a long, hot, dry year are there more of one sex hatching?? I have a feeling there are not but it's just a feeling.
In my experience, I have had both high male to female ratios in some clutches and nearly equal ratios in others just about every year. All incubated at the same conditions.
I'd like to see someone do an in depth study on all this.
It'd be interesting.

link to original post

-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

As far as I remember..

Snakes have chromosomal sex determination just like birds and mammals. It works a little differently in that snakes use the ZW system of birds rather than the XY system of mammals.

So a female mammal has two matching sex chromosomes (XX) while a male has an unmatched pair (XY).

A male bird or snake has a matching pair of sex chromosomes (ZZ) while a female has an unmatched pair (ZW).

Therefore the sex of a snake is determined at the moment of fertilization (depending on the "sex" of the egg). Incubation temperatures do not affect the gender.
-----
Chris Harrison
San Antonio, TX

i gotta disagree with you...
i think temperatures do play a role in Gender as far as reptiles go...there is documentation that it effect the outcome of some reptiles and since ALL reptiles are from a common ancestor there has to be a link.

In Mammals All embryos start out as Female... it's the introduction of the gene Testis which releases Testosterone that changes things up... there is a case of a young lady in the Caribbean (ST. Lucia W.I.) that was born a female 100% when she started going through puberty she grew a penis... i can't find the article but it has happened on other occasions...

don't get me wrong i'm not saying that chromosomes have no role in gender cuz i know better... maybe the temperatures affect what hormone is released?

possibilities:
it could be Brumation temps. (does that effect the male's sperm?)

it could be when we warm them up after brumation (does that effect the male's sperm?)

it could be the conditions during gestation (is the temperature a gravid female is kept at somehow affecting what is released?)

it could be the conditions during incubation (not sure at what point... 1st few days... some where in the middle... or close to the end) [is the temperature the eggs are kept at affecting what is released]

i'm not going to eliminate the possibility that temperatures play a role, till someone does the research

but thank you for the information you provided.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

WOW ZF I know you are sensitive about being called wrong so your "I think you are wrong" must be a missprint. Chris didnt say all reptiles determine sex this way only snakes. I believe he is dealing in science fact while you are dealing in theory. Its a 50 50 chance that doesnt mean you get 50(male) 50(female) outta a clutch. Try flipping a coin and write down the results of 10 flips then do it an aditional 5 rounds of 10 flips and you will see why you can get 8.2 sometimes in a clutch. Also do the coin flips in 84 degrees and then in 79 degrees and see if this has any effect on your results

Keith
-----

i'm responding to the fact that he said "Therefore the sex of a snake is determined at the moment of fertilization (depending on the "sex" of the egg). Incubation temperatures do not affect the gender." (Chris Harrison )

with the explanation he provided his conclusion can't just be adopted as factual. Now, reptiles... birds... mammal they all have "sex chromosomes" whether it be XX, XY,ZZ, or ZW... sex can not be determined at the point of fertilization just because there are chromosomes present.

Human beings can be chromosomally intersexed - that is, XX male and XY female...it's the gene carried on these chromosomes that determine sex not the Just the presence of a particular chromosome. in fact there are many possible combinations such as XO, XXX, XXY, XYY, XO/XY, XX male, XY female, and there are many individuals who do not follow the typical patterns (sometimes having four or more sex chromosomes). for all we know the same thing can occur in our snakes...
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

That would be an anomoly then not the norm. You asked about temp sex determination not odd freak cases. My guess is this has been researched and proven out so I dont see why you are questioning it. Do you have research to the contrary ? Also I was in error you never said he was wrong only that you disagreed, sorry read what wasnt there.
-----

again Keith i was showing that the presence of certain combination chromosomes doesn't necessarily mean what we think.

intersex occurs at a rate of approximately 1 in 5,000 births, making it a relatively common occurrence... not the Norm... but definitely not as abnormal/rare as some may think.

i realized I asked about the relation btwn sex and temperature but chromosomes came up and i had to show that it isn't that simple.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

Now, reptiles... birds... mammal they all have "sex chromosomes" whether it be XX, XY,ZZ, or ZW... sex can not be determined at the point of fertilization just because there are chromosomes present.
Human beings can be chromosomally intersexed - that is, XX male and XY female...it's the gene carried on these chromosomes that determine sex not the Just the presence of a particular chromosome.

I have never heard of an XX male (I'd like to see you find some documentation for that). However XY females occur because the Y chromosomes genes don't function correctly. Normally the SRY gene on the Y chromosome stimulates the gonads to develop into testes, increasing the amount of testosterone and masculinizing the embryo. In the absence of a functional SRY gene, the embryo is female. So sex is determined by the "normally functioning" chromosome of the animal, which is determined at fertilization.

By your logic here, we could argue that sex determination isn't chromosomal because some people hormonally and surgically alter their sex!

in fact there are many possible combinations such as XO, XXX, XXY, XYY, XO/XY, XX male, XY female, and there are many individuals who do not follow the typical patterns (sometimes having four or more sex chromosomes). for all we know the same thing can occur in our snakes...

This further reinforces the point that it is the chromosomes that determine the gender. If not, any chromosome combination could produce any sex, which isn't the case. XO, XX, XXX, and XXXX always produce females. XYY, XY produce males. Only individuals with abnormal sex chromosomes become XY females.

If you have some evidence that snake sex determination works in some other way (and yes, people have looked at this - do some research), you should publish it.
-----
Chris Harrison
San Antonio, TX

you seem to be getting upset because i disagreed with you? by the "Believe what you want.." title

but never mind... thank you Chris H. for the information you provided.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

I'm not at all upset with the disagreement. Simply a conversation. I guess I don't like to see hypotheses put forward without data, particularly when they fly in the face of currently accepted theories.
Call it the skepticism of a scientist?
-----
Chris Harrison
San Antonio, TX

Hey Chris
You have way more of a scientific background than Zenny or myself or at least from what I have read on this and other forums it seems as though you do. I would like to ask you a favor and see if you could tell me if you have seen any research done at other time periods, other than incubation, and if so where. I have always been of the mindset that incubation temps have nothing to do with the sexes of the snakes but I am now wondering about other time periods. You are saying that at the time of fertilization the sex is determined and my question is has this already been proven?

I wonder if in good years in nature when there is a early spring and lots of rain and lots of food because of it if there is a coresponding sex ratio as a result. Or on another level as someone claims below if higher body temps of the female really can change the ratio. A female that is getting more food would keep her temps up to digest and that would indicate that conditions are good so more females would be successful as hatchlings and bla bla bla.

Or I am thinking to far into things. Anyway if there is any study that you know of please send me in the right direction.

Thanks Jason

Hello,
You should listen to Chris H., he sounds like he knows what he's talking about. I did some research on TSD (temperature-dependent sex determination) in reptiles prior to breeding my black milks this year. I wish I could find the link, but there was one site I remember that listed various reptile species and whether or not the gender of developing embryos was affected by temperature. TSD is mainly found in chelonians (turtles & torts), crocodilians, and some lizards. Everything I found indicates that TSD does not apply to snakes, including Lampropeltis. All reptiles may have a common ancestor, but how do we know that ancestor had TSD? Even if it did, and some of its descendants still do, what would prevent other branches of the evolutionary tree since then from developing a different system?

As far as sex determination in mammals... it is determined primarily by the 23rd chromosome. XX for females, XY for males. Testis is not a gene, it is a testicle... genes are the protein sequences (DNA) contained in chromosomes. It is true that male and female embryos start out with genitals that are similar in appearance, but the actual structure is different from fully developed male or female reproductive systems, and actually has primitive elements of both. Even though the structures for male and female genitals are nearly identical at early stages, there are some observable differences. I saw a really interesting show on fetal development on the National Geographic channel on Saturday afternoon, and I found out that a skilled OB/GYN can actually make a good guess based on the angle of the shaft that will later develop into either the penis or clitoris. Due to chromosomal or hormonal abnormalities, it is possible for children to be born with intermediate or ambiguous genital structures. The young lady you described probably has congenital adrenal hyperplasia. The link below has tons of information on that I hope will help you get your facts straight.

Nate
Human Sexual Determination

Thanx for pointing out my error... i didn't even realize... it's kinda embarrassing now that i read it over.

to correct myself above the SRY gene allows the gonads to become Testes and the Testes produce testosterone (in all the typing i wrote the wrong thing)... but i do know what i'm talking about... it's not as simple as XY or XX

thanx
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

Hey Zenny,
As far as I have read/heard snakes are in a sort of limbo as to their relation to other reptiles. The things I read can place the closest relative to turtles and crocs and most lizard/skinks with some agreement but with snakes there is either no placement or no agreement with those in the science fields that do place them. Everybody agrees they are reptiles and that they are snakes but as far as to what is the most primitive snakes it gets all messed up and argumentative not unlike here. The relation to other reptiles is not really understood either. So to use info on other reptiles that are vastly different can be misleading.

That said I hope something is determined and I think as I said below that we have a vastly unused resource here. I would like to post next year or even this year breeding results. Who produced what and how many of each and what conditions where used. This may lead to confusion but if done right it could present alot of data even if it is somewhat incomplete. Also as I said below the deformities that occur with the relation to the sex of the animals might be useful on a large scale.

Good Topic

later Jason

ok... i got what you're saying... i'm not saying because it happens in turtles it has to happen in snakes... I'm trying to figure out if there is any relation...

I'll work on figuring this out when i get a pair of low budget snakes... I'd hate to play around with my project animals... to figure this out.

l8r
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

I have read a little bit on temperature dependent sex determination. As far as I read, most of the mechanism was understood. It works off of a positive feedback system with the average daily temperatures up to the middle trimester of embryo development determing the sex of the embryo. At temperatures that produce females, , the enzyme aromatase is induced and converts testosterone to estradiol (an estrogen). Estradiol binds to the estrogen receptors on the undifferentiated gonads triggering their development into ovaries, which in turn synthesize more estrogens. Estrogen production causes a positive feedback which in turn induces more aromatase production. At temperatures that produce males, reductase is induced and converts testosterone to dihydrotestosterone. Dihydrotestosterone binds to androgen receptors on undifferentiated gonads and triggers differentiation into testes. The testes then begin to produce more androgen which leads to positive feedback and more reductase is induced.

There are also three different patterns of TDSD as far as I know. Pattern 1 – Most turtles, where males are produced at cooler temperatures and females at warmer temperatures.
Pattern 2 – Some lizards, females are produced at cooler temperatures and males are produced at warmer temperatures.
Pattern 3 – Some turtles, lizards, and all crocodilians, where females are produced at warm and cool temperatures while males are produced at intermediate temperatures.

Also keep in mind pivotal temps, where you get an equal ratio of males to females.
This is simply my understanding of the mechanisms involved with TDSD from some of the different journals I read.
Hope some of this may have helped.

Cheers,
Bryan
-----
roomates:
anery corn "zepplin"
normal corn "little bub"
eastern garter "auspicious"
broad-banded watersnake "washington"
Australian Cattle Dog "Pounder"

Now that i can work with... Thanx...
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

No prob, Like I said, only my interpretation. If you are interested, I can dig up some of the old citations I read.

Cheers,
Bryan
-----
roomates:
anery corn "zepplin"
normal corn "little bub"
eastern garter "auspicious"
broad-banded watersnake "washington"
Australian Cattle Dog "Pounder"

i am interested ... very interested ... thanx in advance for any info you'll provide.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

O.K., it took some diggin but here are a few.

Janzen, F.J. 1995. Experimental evidence for the evolutionary
significance of temperature dependent sex determination.
Evolution, 49: 864-873.
Ewert, M.A. and C.E. Nelson. 1991. Sex determination in
turtles: diverse patterns and some posible adaptive
values. Copeia, 91: 50-69.

Vogt, R.,J.J. Bull, C.J. McCoy and T.W. Houseal. 1982.
Incubation temperature influences sex determination
in Kinosternid turtles. Copeia, 82: 480-482.

As far as outlining the process, some herpetology books go deep into the process, some just mention it in passing. I hope this helps.

Cheers,
Bryan
-----
roomates:
anery corn "zepplin"
normal corn "little bub"
eastern garter "auspicious"
broad-banded watersnake "washington"
Australian Cattle Dog "Pounder"

thank you for taking the time out... i do appreciate it.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

How about an actual approach, temps have not been shown to effect sexes in snakes(yet) And have been shown to effect sexes in some other reptiles.

Of interest, my bet is this is a manmade effect. The species that it has shown to occur in, are surface nesters, that is, they deposit their eggs on or very close to the surface(less then a foot deep) With that in mind, their normal natural incubation would indeed include flucuating temps. It would be impossible to not have that occur. Man for some silly reason, incubates at a constant temp. May I suggest that this is not normal nor the design of these species eggs. They were designed to incubate in a range of temps. Now the question is, why do we incubate them at constant temps? Also, its been shown that including the same temps that cause high males and high females will express an even percentage. Wow, how odd is that.

Reptiles that place their eggs in areas of constant temps, do not seem to respond in the same manner, they seem to have other mechanisums to achieve both sexes.

Consider, reptiles being ectotherms depend on their surrounding enviornmental conditions to achieve and support many phyical processes.

If your concerned with the actual biochemistry that causes this, I would suggest going to where there are actual biochemists. I do not think many here fully understand or have a need to understand that part of the process. Good luck, FR

Thank you FR
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

... I found that by just going with the natural temp. fluctuations I have here in FL. (actually sometimes in the 50's at night in March)I have had a much better overall hatch--healthwise. I mean, no kinks or deformities at all and only a few high male to female ratios now and then. The highs obviously get into the mid 90's during the summer months but as a rule I'd say the mean temp would be in the high 70's to mid 80's. Just fine it seems for my kings, milks, and corns.
When I used an incubator I had more problems than they were worth, really.
As a side note, yesterday I found these two clutches of eggs (you can tell the differences by color here,and closer inspection showed smooth shells of a rat snake and a rough ones of the racer) that were deposited in a rotten palm when I noticed a small shed skin.(barely visible corn snake skin lower right)

One clutch is a southern black racer (I counted 14)and the other is good ol' corn snake(9).So at least these two snakes can use the same stuff. All were slit and appeared to hatch out o.k.
I've found other eggs in these palms too over the years.
:Mark

thanks for sharing!

This year I have had an almost 100% male hatch ratio. I have 5 more clutches to go this year and I will bet they will be all male. I just had 3 clutches hatch this weekend and just sexed them and again had all males. This has happened on my last 10-12 clutches. The clutches before that I may have had 1 or 2 females out of say a 8-12 size clutch. The other clucthes were all male. Incredible odds don't you think?

The only thing I did different this year was during brumation. I incubated the eggs the same way I do every year.

Now a result like this is the reason i asked the question... if sex was determined merely by the chromosomes your outcome would be rather different... i assume you've been using these same snakes for some yrs. and your sex ratios haven't be this dramatic in past yrs?
and now that you've change the brumation temps. you get a HUGE number of males in every clutch... badluck?... i really don't think so.

i'm not 100% sure you gave me all the conditions your snakes were under this season the first time i post this question... i'll 2x check but if you didn't can you please give me the conditions...

Thanx
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

You are correct in saying the same females and same males were used and I got normal ratios in the past year. Whats also interesting I double and triple clutch most of theose adults and they still had all males.

I coooled my animals way below what I normally do. Usually I give them a hot spot and the room gets dips down into the high 30's and 40's. They can thermoregulate this way all winter moving to the warm side if they choose. They always seemed stayed on the cool side so this year i did not turn on the heat because i thought I would get try something different to possibly get an early start breeding and to make sure these snakes cycle properly..

The second thing I did different was warm them up early and feed them before inroducing the pairs. What I normally do was wait until the outdoor temps and natural season change occurs and then throw them together to breed with no feedings. This usually occured in March. This year I heated them up in mid feb and fed and fed them until they bred (rather late) in April.

So I can't point to what caused the possible high male ratio(?) It could have been the low temps with no choice for them to thermoregulate. Or it could hgave been the heat I turned up on them in mid febuary and kept them on until they bred in April.

Who knows it could be a combination or other factors related to this that caused the significant high male ratio. The bottom line is I DID SOMETHING TO CAUSE THIS. Every clucth was males. After about 25 or so clutches ya think it was "bad luck". HA! After predicting (and hoping) this was not the case I have had to pop male after male this year. I probed and double probed every possible female and still all males. Like I said I don't even have to sex the next few clucthes this year because I alrady know they will be all male. Actually I will but i am a bit jaded at this point.

.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

I really love the field stuff Rainer and since I saw ZERO live snakes yesterday, I was looking for just about anything. I noticed the shed skin and just had to investigate further as the little guy might have been inside. He wasn't and after I saw the first few eggs, I nudged a bit more and the others were right behind those.
So all your PB&J's are male???
See, that's just karma man, for doin' me like ya do.

:Mark

First, your right, that is very odd percentage, particularly over time. I have had(in the old days) several clutches that were all male. What is of interest is, I do not believe I ever had a large clutch be all female.

As you know, temp sexing by temperature incubation is not known in snakes, but no one has investigated controlling the adults. Its entirely possible.

But, there is a large "little known" curveball to consider and investigate. Are your seatbelts on and secure?

As of the last few years, parthnogenetic reproduction in snakes has been documented(Dr. Gordon Shuett, ASU West) Also, years ago, at the end of my working on getulus, I tried to publish multible occasions of parthnogenetic events.(got shot down)

In both Dr. Shuettes and my events, the offspring were all males. Actually he documented two types of parthnogenetic pathways and only one type resulted in all male offspring.

With this in mind, do you have reason to believe that this is possible? for instance in my cases, the females were never bred to a male(in their entire lives) that was of the same color pattern(morph) as them. For instance, one female was a desert B&W, sidebared calking(the first captive bred) She was only bred to brown and yellow and melanistic, males. The brown and yellows males were both San Diego striped and newporter striped(dashed) morphs. So in all her clutches, she had offspring that resembled both parents(mutts) none ever was exactly like one or the other parent, a few that were very close, but always exhibited some taletail clue. After many years, I did not want anymore offspring so I did not put a male in with her. On these occasions, she still laid good eggs that hatched, only they all resemble only her, no influence of any male she had bred, and, all were males.

I did this with three individual females, maybe more, but I only had a complete life history on these three(virgins when obtained)and never bred them to a male with a like color pattern and color.

As I mentioned above, I also had several other clutches that were all males, but did not have evidence that no male was envolved. For instane if the males were of the same morph, then you could not tell if their influence was missing.

So its possible your new brumation temps are not allowing viable sperm and the females have resorted to parthnogenetic reproduction. I would look into this. It may be a possibility as to why you have so many males.

Whats important about this is, while parthnogenetic reproduction is known in kingsnakes and other types, its not understood how to consistantly encourage it to occur.

Of course, it could be what your indicating. Again, contact some institution that may be interested and have it tested with usable controls. Thanks for sharing, FR

Owww. Thats a tough one to answer because as you know, I work with some hybrids and if parthenogenetic young were produced they all looked different because thats what 2nd gen hybrids do.So no way to tell if they looked like the mother.

I also double and triple clutched females with the same high male ratios. Would it be possible the parthenogentic pathways were working overtime?

For instance I did several breedings with one particular hybrid (speckled king x albino yellow rat) that was a first time het to het breeding. Both females double clutched and in the four clutches I had albinos, so is it possible to get the recessive traits reproduced from the female from parthenogentic reproduction?

Couple things I forgot to leave out in my original post. I must have thrown away about 400 eggs this season that were infertile. Most of these came from females that threw all infertile clucthes and then produced 25% or less fertile eggs in the second clutches so another 75% of those clutches were bad. Never had such a bad year.

The second thing that happened is I had about 6 females get eggbound on me on their first clutch. This is also unusual since these were seasoned breeders i have successfully bred the last few years and had zero problems with.

Below are the sapeckled king x yellow rats mentioned above. Out of four healthy sized clutches, I got TWO females. This was typical of my ratios this year.

If they were products of parthnogenetic reproduction, they were appear like the mothers type, not exactly like her, her type.

If the offspring have evidence of both parents I would not think they are of that.

Also, I have no experience with keeping any reptile at an exact temp, I always have offereed choices for them to choose from. So I would not experience what you fellas seem to be experiences. I will say, if I got mostly males, I would change what I am doing and offer the adults more choices. Unless you want all males.

If you changed the conditions, and it changed your results, you fellas may be on to something. Good luck FR

I agree, we incubate all our eggs with a far amount of variation. That includes turtles, torts, snakes and monitors at this time.

I kinda think one exact temperature is totally manmade.

This spring my son dug up some hatched gophersnake eggs while digging up turtle eggs. He was sort of dumbfounded. He kept wanting them to be turtle eggs, hahahahahahaha, I said, they are slit and cracked open, hahahahahaha he threw them at me. Thanks FR

Hi Everyone

In 1989 i started a little experiment with ratio's in mind.
at the time i was playing with cornsnake Patterns and wanted far more females than i was getting so i tryed this on 3 of my females.
1 female = after 2 successfull matings i would keep the female at a constant temp of 88 until she laid.

2 female = the same as 1 but constant temp of 82 until she laid.

3 female = again the same but constant temp of 75 until she laid.

The incubation of all the eggs concerned was never manipulated and kept as i normaly do which is a temp of 85 and 90% humidity.

The results.

1 female = always 70-80 female hatch.

2 female = Random 60/40 40/60 flutuating over the years.

3 female = at least 70% male

iv used this system ever since on corns kings and milks and get virtualy the same results every time,by which i meen about 99%.

i wish i new all the scientific terms like you guys, then i could of sounded a bit more pro, lol .

So the incubation temp (in the inc) doesnt matter.
it seems to be the temps leading up to the incubation.

I hope you guys try it, you will be pleased with the results you get. it great to have just that little extra control.

A WORD OF WARNING..
i had one clutch of corn x pueblan x nelsons (only one clutch)this year and kept the female at 88 and got all females. gutted i was expecting at least 1 male but not one. oh well sh-t happens now and then.

Sorry for the spelling.

Paul..
-----
Pinky's taste nice,only if there fresh..

Thanx for the information you provided... i'll test this out.
-----

Thanx
Royal Blue Reptilez

~ZF
Bkyln's Finest Brooksi & Goini Fanatic

That is interestings data. I would like to see you someone formally confirm this with more good data. Perhaps Neil Ford at UT Tyler might be interested in doing some work on this since he breeds a lot of snakes for research.

You might want to consider an alternative hypothesis to explain your data. It is possible that different eggs (Z vs W) might have different survivability during oogenesis(prior to fertilization). If female eggs have higher survival at higher temps, there would be a greater chance of producing female embryos. But this is NOT temperature dependent sex determination, per se. It is still chromosomal sex determination.

This question would be better answered by karyotyping a few snakes than any breeding surveys. An experienced cytogeneticist would be able to tell pretty quick what the gender/chromosome relationship is (and it may have already been done?).
-----
Chris Harrison
San Antonio, TX

You should have a look around and see if you could get some herp department interested in your work, with some more work, it could be very very important. Good luck. FR

Thankyou for your replies.

Im not a very scientific person, but i have got complete data going back to 1987 which includes 3 years experimenting with egg temps in the incubator of which every clutch produced just random male/female percentages as you would get with normaly incubated eggs, i was going to give up playing with the eggs but realized that the female is allready incubating the eggs that she's carrying, so thats what started me off with the temperature changes to the females carring eggs. the temps in my previous post are the most optimum temperature manipulations for the male/female ratios.

during the first few years of manipulation to the female's temps i also found that useing a temp range of 90-94 produced findings of egg binding and fertile but sticky eggs , kinking, and heavy deformaties and i lost more than a few females along the way,but temps of 90/94 constant for an average of 8 weeks is hard going for any snake really.i dont like being cruel to any animal, but for the experiment that i was trying i had to do it. after three seasons i droped the very high temperature ranges completly.
allso i tryed some pre mateing temperature experiments on males , some of the results were very pleasing but most were not,it seemed to reduce the productive efforts from the males drasticly.

Paul..

-----
Pinky's taste nice,only if there fresh..