Sex Determination

[colinmelsom]

What are the current theories on sex detemination in Phelsuma?How is it possible to breed more males?

 

[Sgvreptiles]

Depends on species.

 

[colinmelsom]

How about cepediana ,guimbeaui,inexpectata and ornata?

 

[PrestonG]

Well for Cepediana it is said higher incubation temps 86-87 with a drop at night. There is "some" research done by Leann Christenson to back this up but it only increased the ratio of males to female and also at a cost of a far higher neonate mortality rate as well as dead in shell occurrences.
not sure on the others spieces.

 

[PhelsumaUK]

I don't think Phelsuma exhibit TSD in the same way some other reptiles do and there are several difficulties with the postulated hypothesis. There may be an effect as a result of incubation temperature but the link isn't strong with many species and less so with the Mauritian species. Not sure that its as simple as female embryo mortality at higher temperatures either. There might be a link between sex and speed of embryo development which would be affected by temperature. Also doesn't appear to be linked to maternal yolk hormones. I'm playing with another idea at the moment (but in a half hearted way!). If it yields any promise this year, I'll do it properly next year...Then after that there's plan #11 and #12! That's the problem with Phelsuma...it takes time to get a large enough breeding program together to get enough eggs to work with and then you only get enough to put one or two ideas into practice each season....and then of course you end up with having to raise up more hatchlings than you want/need to a sexable size to see what the result was.

So the answer is Colin..I still don't know! (but I can do cepi females very cheaply!)

 

[colinmelsom]

Thanks for the answers,I suspected it wasnt as easy otherwise male Mauritian species would be more readily available and cheaper.
I have never been lucky enough to visit these islands but I wonder whether females predominate here? It would seem a good survival technique as males are more aggressive and can mate with more females which would ensure the continuation of the species.
The problem seems with the Mauritian species as I regularly visit The show in Hamm and the males of the Malagasy species are easier to come by and therefore cheaper.
The only spanner in the works seems to be P.borbonica from Reunion which seems to be mor male orientated as there seem to be more available than say cepediana or guimbeaui.

 

[PhelsumaUK]

I've already looked into the sex rations in the wild..Apparently there's no disparity.

re the borbs...could it be the same males going around from keeper to keeper on account of their willingness to shred up females? I've only bred a few borb mater but got about 70% female hatchlings.

 

[colinmelsom]

Perhaps I have been lucky with my borbonicas,my males are placid.I will let you know on the ratios assuming the eggs hatch

 

[LLDG]

Well for Cepediana it is said higher incubation temps 86-87 with a drop at night. There is "some" research done by Leann Christenson to back this up but it only increased the ratio of males to female and also at a cost of a far higher neonate mortality rate as well as dead in shell occurrences.
not sure on the others species.

Five years of studies done by multiple keepers show that indeed the ratio of males increases when the daytime incubation temperatures are in the 85ºF-89ºF range and drop nighttime into the high 70's.

The neonate mortality was seen primarily when the incubation temperature was a constant day and night temperature anywhere from 89ºF-91ºF. One year of this convinced us not to try this again.

Dropping temperatures at night seem to protect the neonate, and the mortality rate decreased significantly.

Last year the offspring ratio of Male to Female was 3:8. With the delicate nature of the females, the ratio is very suitable. The females are shorter lived and more susceptible to stress related deaths.