Temperature influence on sex determination

[sergé]

Dear friends,

has any of you tried to do experiments with eggs or larvaes of caudates?
I found an abstract of an article by Wallace & Wallace (2000; International Jounral of Developmental biology) in which they have kept Triturus cristatus l}arvae at different temperatures, and guess what...trials at 18-24 degrees C turned out 1:1 sex ratio, lower more females and higher more males.
I have raised my T. pygmaeus mostly at temperatures below 20 degrees Celcius and I mostly had more females than males (which fits to the Wallace and Wallace experiments).
- Are there other publications on this subject knwon by you? For instance on Axolotl's (as they are probably the most investigated laboratory caudate around).
- Are there people among you who have tried to experiment with this?
It is a very simple experiment; so there must be some experience among you!!

greetings, Serg}

 

[claire]

That's really nice that you found this abstract.
Dr Hugh Wallace used to lecture me -he was a real character and the source of my first lot of axolotl spawn

He's retired now and sadly missed but his wife's still around. If anyone wants the full text of this article just ask and I'll email it to you.

 

[claire]

More recent research citing the Wallaces:

Differential expression of P450 aromatase during gonadal sex differentiation and sex reversal of the newt Pleurodeles waltl
Kuntz S, Chesnel A, Duterque-Coquillaud M, Grillier-Vuissoz I, Callier M, Dournon C, Flament S, Chardard D
JOURNAL OF STEROID BIOCHEMISTRY AND MOLECULAR BIOLOGY
84 (1): 89-100 JAN 2003

Abstract:
A better understanding of vertebrate sexual differentiation could be provided by a study of models in which genetic sex determination (GSD) of gonads can be reversed by temperature. In the newt Pleurodeles waltl, a P450 aromatase cDNA was isolated from adult gonads, and the nucleotide or deduced amino acid sequences showed a high level of identity with various vertebrate species. In adults, aromatase expression was found in gonads and brain. In developing gonads, the expression was found to fit with the thermo-sensitive period (TSP) and was detected in both ZZ and ZW larvae, as well as in ZW submitted during the whole TSP to a masculinizing temperature. In the latter individuals, in situ hybridization and semi quantitative RT-PCR showed that, at the end of TSP, aromatase expression was at the same level than in normal ZZ larvae and was significantly lower than in normal ZW ones. Furthermore, temperature-induced down regulation did not occur when heating was performed at the end of TSP. Our results confirm the importance of aromatase regulation in female versus male differentiation and demonstrate that a down regulation of aromatase expression is involved in the process of sex reversal.

And here's the Wallace's abstract:

Sex reversal of the newt Triturus cristatus reared at extreme temperatures
Wallace H, Wallace BMN
INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY
44 (7): 807-810 OCT 2000

Abstract:
Crested newt larvae were reared at defined temperatures, either from uncleaved eggs or from early feeding larvae, until metamorphosis when sexual differentiation had occurred. Trials at 18-24 degreesC showed a 1:1 sex ratio. A higher temperature trial produced more males than females, including some XX neomales, Lower temperatures resulted in a significant excess of females, including XY neofemales. Sex reversal only occurred in about half the possible cases on average. Extreme temperatures must perturb the normal XX/XY system of sex determination, to reveal either an ancestral ZZ/ZW system or a still more primitive environmental control. It is suggested that neofemales (but not neomales) could occur in nature.

 

[fabian]

Hi,
I can't call a "experiment" but an experience. In 3 breeding years of Taricha granulosa I've got much more male than female (I don't know about all the animals because I gave away most of them while they were juvies). Perhaps about 8:2 (male:female). I haven't protocolled my temperatures but they were in an range from 16 to 24°C. I've heard from other Taricha breeders they also have much more male than females. On the other hand my first three granulosas (I bought them as cb juvies in a pet store in Dortmund, I don't know who has bread them and on what temperatures) turned out to be all females. So these are my experiences not very scientific I think...
I have one question to this matter: At what time in development takes the sexual determination place? Is it all done before hatching or in larval stadium or even after metamorphosis?
Fabian

 

[jennifer]

Interesting stuff. I wouldn't try the experiment myself, as I'm most interested in raising offspring that will have full breeding potential.

There are also some other (older) references regarding temperature effects in the Pleurodeles caresheet on Caudate Central:
http://www.caudata.org/caudatecentral/caresheets/P_waltl.html

 

[aaron]

Temperature Sex Determination is common in many herptiles, and I wouldn't be surprised if this proves true in caudates. If anyone decides to experiment with this, please keep us updated.

~Aaron

 

[caleb]

I'm no expert on this... but I was under the impression that the reptile species that exhibit temperature-dependent sex determination, never have chromosomal sex selection.

It would be interesting to know if the individuals that have changed sex still produce sex chromosomes in their offspring as if they were the original sex: an XX 'neomale' bred with a normal XX female would presumably be expected to produce 100% females!

Also, there's a note in Pat Wisniewski's book 'Newts of the British Isles' mentioning that starved male alpine newts have been known to change sex- I've never managed to track down the origin of this assertation.

 

[han]

Serge,

Not sure whether there are any publications on this subject, but during the early eighties the University of Utrecht (Netherlands) did some research on genderdevelopment and temperature using Bombina orientalis. Because i contributed some 50 toadlets to that research, i recall some personal information by one of the researchers:
they found (as far as Bombina was concerned!)
22.8C to be the temperature where genderdevelopment was 50/50; more males at higher temps; more females at lower temps.

Han.

 

[mike]

In several species of fish (e.g. Pelvicachromis pulcher), pH also plays a role in sex determination. Just something else to consider!

 

[sergé]

Dear friends,

thanks for the information. Yes in reptiles a lot of studies have been done. I remember one on Leopard gekko's where morphological females reacted as males for instance due to over or underheating.
Claire: I would really like a copy of the full article. I have e-mailed Dr. Wallace, but as I now read is he retired...he didn't respond his e-mail. I'll send you my details by e-mail.
In Pleurodeles this phenomenon has been researched by french scientists and it turned out different for P. waltl than for P. poireti.
For me the main reason is that especially for rarer species it would be interesting to see if you can 'steer' in this. I mean you just need one male for several females, and for aggressive species it is even better to have lesser males.
Taricha would be nice to do research on.
Well, hope some more idea's will come.
Serg}