Mechanism controlling sex ratios

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Mechanism controlling sex ratios

Postby Stijn on Tue Nov 07, 2006 3:35 pm

I foudn a very interesting article

Nuclear Sex-determining Genes Cause Large Sex Ratio Variation in the Apple Snail Pomacea canaliculata. from Yusa Y.

The main conclusion: at least four nuclear genes control the sex determination in apple snails. In humans we talk about XX (girl) and XY (boy). In apple snails it would rather be: V, W, X and Y combinations. Unfortunately the actual genes and the mechanisms haven' yet been elucidated. But I suppose that one day, the mystery around apple snail sex ratios will solved.


Abstract

Code: Select all
Evolutionary maintenance of genetic sex-ratio variation is enigmatic since genes for biased sex ratios are disadvantageous in finite populations (the "Verner effect"). However, such variation could be maintained if a small number of nuclear sex-determining genes are responsible, although this has not been fully demonstrated experimentally. Brood sex ratios of a freshwater snail Pomacea canaliculata are highly variable among parents, but population sex ratios are near unity. In this study, the effect of each parent on the brood sex ratio was investigated, by exchanging partners among mating pairs. There were positive correlations between sex ratios of half-sib broods of the common mother (r = 0.42) or of the common father (r = 0.47). Moreover, the correlation between full-sib broods was very high (r = 0.92). Thus, both parents contributed equally to the sex-ratio variation, which indicates that nuclear genes are involved and their effects are additive. Since the half-sib correlations were much stronger than parent-offspring regressions previously obtained, the variation was caused by zygotic sex-determining genes rather than parental sex-ratio genes. The number of relevant genes appears to be small.


Abstract here:
http://www.genetics.org/cgi/content/abstract/genetics.106.060400v1

Full article here:

http://www.genetics.org/cgi/rapidpdf/genetics.106.060400v1
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Postby luvfishies on Tue Nov 07, 2006 11:23 pm

Very interesting! I didn't check the links out, but your inserted piece was intriguing.

I'll check the links out later when I'm not pressed for time :D
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Postby badflash on Wed Nov 08, 2006 12:08 am

Hmmm.

I got some canas from the pet store last year. They were likely all sibs. I ended up with a male and 3 females. All of the offspring were females, and when they were mated to the father, all of their offspring were females. I never got a single male from that batch. I sent some tiny babies to Luvfishies. I'm betting they were female too.

Luv, am I right?
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Postby luvfishies on Wed Nov 08, 2006 5:44 am

Hmmmm. Here they are from a while ago when I took snaps of them lettin' it all hang out.

Snailie 1
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Snailie 2
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I thought they were one of each, but on closer look-see, it's hard to tell. I should really get them out and snap some more pictures of them.
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Postby Becca3711 on Wed Jun 06, 2007 5:43 am

They both look like males to me.
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