Suppression of male alpestris?

[jennifer]

In a previous thread, we were discussing the fact that some batches of captive-bred M. alpestris seem to be predominantly females.
http://www.caudata.org/forum/messages/13/68688.html?1159721583
I have a new discovery that might be an explanation for this.

First, the history...
Last year (fall/winter/spring) I kept a large tank with 11 alpestris apuanus. They were a combination of 2:2 second-year animals, and 7 "unknown" first-year offspring. Throughout the breeding season, all 7 of the younger animals were "female". At least SOME of the first-year females produced eggs.

This summer, I sold 5 of the young "females", and kept 2. I also acquired 2 additional 1-year-old "females" from another source. I moved these 4 animals to their own tank.

Here are current photos of my 4 "females":

Clearly 2 of them are male, and there is a third one that may also be male. (Anyone want to make bets on the sex of #4?)

There are two explanations that I can think of. First, perhaps SOME males require longer to develop. Second, perhaps the presence of a stronger male(s) somehow suppresses the development of breeding characteristics in young males.

What people have observed in groups of CB offspring is that one or two of them develop very quickly into males, and all the rest look female. People think they are able to sex them at this point. But really, maybe there are additional "hidden" males among the ones that still look female.


(Message edited by jennewt on October 12, 2006)

 

[frank]

I had similar experiences with Triturus vittatus vittatus: in their first year, the offspring apparently consisted of only a single male and 8 females. However, the following year, 7 of these "females" started developing crests during their terrestrial phase and turned out to be males...

 

[alan]

I have observed this too, but even after the late developers emerge, there is still a slight excess of females over males.

 

[michael]

I've been able to sex out quite a few males from this years hatch. I'm telling people they are definate males and probable females. It seems males reach sexual maturity before females in many newts.

 

[charles]

#4 looks like a female turning into a male. I wonder what would happen if each newt had it's own tank?

 

[william]

Interesting Jen! I think that apparently large numbers of female marmoratus develop compared to few males has also been identified.

 

[joseph]

I know with some fish(popular example, swordtails) their are often late maturing males which can pass as females for the first year or so while they are gaining size. Then they suddenly turn into large males. In some species of swordtail the rates vary enough to produce early maturing "sneaker males" who are tiny and unimpressive and pass on their genes by stalking and mating with the females unnoticed, to large males taking over a year to mature that keep territories(the ones the hobbyists prefer of course).

 

[ravenous]

Those are some awesome looking newts. Im no expert, but could temperature affect their sexing? I remembering reading thats what effects the sex of turtles.

 

[edward]

Unlike chelonians caudates use a genetic sexing mechanism and true TSD is not known to occur in caudates (there are a couple of examples where exposure to excess temps changes the expressed sex but the genetic sex is still correct).

Ed

 

[kamil]

Hi Ed,

do you have any Literature on that?

 

[jennifer]

Just for an update, here is the same group of 4 alpestris today. Animal #4 is certainly female, and she's laying fertile eggs. Animal #3 is still looking female, but not looking gravid.

P.S. to Kamil: I have seen this information (genetic sex determination in caudates) in amphibian textbooks. I can try to find the references where I saw it, if you're still interested.

 

[rodrigo]

Interesting.
I know of this happening with other animals, but didn´t know caudates had it. Specially since they aren´t social animals.
Male supression is known in reptiles, and even in elephants.
btw...i´d say number 3 is a male...it´s got a crest.

More info on this please n_n

 

[charles]

Jennifer, I think you meant #1 because #3 looks like a male to me.