# What effects gender



## Lissa_678 (Mar 1, 2010)

I have five young platies (about 6 months old) that I managed to raise successfully and for some reason all five of them are male and harrassing my two moms..

I was wondering what dictates the gender of the fry? Is it temperature, timing, or just odd luck?

Thanks


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## chamfishlvr (Jan 22, 2010)

I don't really know, but it's probably like humans. 50/50 chance of being male/female, and you just ended up getting all males. >.< hopefully you can get some more females, or i would just give 'em to a pet shop or sumthin..... unless you want them.

good luck!


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## PaulLamb (Nov 15, 2009)

Livebearer sex determination is somewhat different than how it works in humans, because it evolved along a completely different branch. Sex determination is rather plastic when you look at the group as a whole. Because of this plasticity, livebearers have been studied extensively by geneticists. In livebearer species where there are two sexes, determination is achieved through an amazing variety of genetic mechanisms, which span from simple XX-XY or ZZ-ZW systems to polyfactorial sex determination, so it is not always as set in stone like it is in humans. Some members of the genus Xiphophorus, for example, can change sex from female to male when they find themselves in an all-female environment. There is even a species of unisex livebearers where all are females and they give birth to perfect clones of themselves.

This was probably a complicated answer to a simple question, but nature isn't always so simple.

--EDIT-- I just realized that I didn't answer your question specifically about platy sex determination. In platies, sex is believed to be determined via simple paired sex chromosomes. However it is important to note that platies, being members of the genus Xiphophorus, have been hybridized with swordtails by breeders on various occasions for the purpose of transferring various desirable genes between the two species. Swordtails are one of the polyfactorial species, and are known to be sex-changers (females becoming males when trapped in all-female communities). This capability may have been transferred to some varieties of platy, so who knows what is really going on behind the scenes..


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## PaulLamb (Nov 15, 2009)

Another thing that I have personally observed (I'm sure it has been better documented by others), is that livebearer species often employ an interesting survival mechanism that is related to gender. The females are far more valuable to the species than the males are, since females must carry their offspring to maturity, and you only need one male to impregnate multiple females. Because of this, the males are impaired in some way compared to the females, making them easier targets. Since they all school together, this makes predators more likely to eat the males, allowing the females to escape. Male impairment is achieved in different ways, depending on the species. For example, in endlers guppies, the males are brightly colored while females are camouflaged. In swordtails, the sword generates drag. In Gambusias, the males are smaller, slower, and weaker than the large, robust females.

I haven't done any actual counting, but it may be possible that the percentage of male fry is a bit higher than female fry because they are more vulnerable. Perhaps some breeders have solid numbers to support or refute this theory?


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## NatBarry (Feb 19, 2008)

I cant be sure but ive heard that when the temperature is put up slightly higher say 83-85 degrees then the fry are more likely to be female, but im not sure.


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## PaulLamb (Nov 15, 2009)

I read a study on guppies about temperature and sex. It is possible that the same may apply to platies.

In the study, the effect of temperature on survival and sex ratios was investigated. Treatments of 19, 21 and 22.5°C low and 29, 32 and 35°C high water temperature were used on gravid females. Survival rates of the fry were generally decreased by both increasing and decreasing temperatures. The proportion of females increased gradually with decreasing temperature and the proportion of males increased gradually with increasing temperatures. These results suggest that one or more genes linked to the male chromosome could be responsible for resistance to high temperature and sensitivity to low temperature.


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## Guest (Mar 2, 2010)

temp deff effects the sex of fry in live bearers.....the guppies that bred over the winter were all female and now with the temps nice and warm they are dropping males. when the temp was around 80's i had a nice mix of males and females. so basically, Higher Temps = more males, Lower Temps = more females and Mid Range Temps = decent spread of the sexes


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## emc7 (Jul 23, 2005)

I don't know about livebearers, but both temperature and pH effects on sex ratio have been documented in cichlids and possibly in Killies.


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## PaulLamb (Nov 15, 2009)

Zakk said:


> so basically, Higher Temps = more males, Lower Temps = more females and Mid Range Temps = decent spread of the sexes


True observation, but I think an equally important result from the study I mentioned was that temperature fluctuation _reduced the total number of fry_. This means that the temperature didn't determine the sex of individual fry, but rather it determined which sex were more likely to survive to birth. I think that is an important distinction, but of course the end result is the same: higher temps mean more males, and lower temps mean more females. At least this is what was found in guppies - platies may very well be different.


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## Guest (Mar 2, 2010)

i am lucky that way.....i dont have temp flux's which keeps the water constant...but yes....during the monsoons the spawn numbers were very low due to the constant fluxing of the weather. i have bred platy and swords as well and this temprature theory effects the them as well. not restricted to guppies


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## PaulLamb (Nov 15, 2009)

BTW, I reread my post and realized I shouldn't have used the word "flux" - The study was about colder temperatures and warmer temperatures affecting survival rates, not about fluctuating temperatures.

If anyone is interested in reading the study I was referring to, it is entitled "Effect of temperature on sex ratio in guppy Poecilia reticulata" by Karayücel, İsmihan; Ak, Orhan; Karayüce, and Sedat; and it was published in Aquaculture Research, Volume 37, Number 2, February 2006 , pp. 139-150(12).


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## TheOldSalt (Jan 28, 2005)

Hmmm....interesting.

I can attest to one, thing, though; cranking the temp even higher will flip it around again, resulting in a much higher percentage of females. My outdoor pool reaches 100F every summer for weeks on end, and I always get about three times as many females as I do males. Actually, to be more precise, I always have three times as many females survive long enough to be identified as such. It may well be that I'm getting more males but they quickly die. It isn't an easy thing to sift tiny fry out of a pool to check.


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## Lissa_678 (Mar 1, 2010)

Awesome! Thanks for all the replies, everyone. I do intend to trade four of the males to a local pet store in return for credit so I can get some more variety. 

I started out with one Red Wag female, one White Wag female and a male that was orange with a black speckly tail and rear end. At the store they were just marked as "mixed platy" so I'm not 100% sure what they all are. The fry are a mixture but they all either look like one of the adults, or are completely speckled (some are white, some are orange..). 

I actually have about 30 fry now, but its just the 5 males that confuse me.. I know they're all from one batch and seperate from the rest because they were dropped from the white female in a seperate tank and were raised away from the other fry. Of course there were more than these 5 when I started but lost a few due to lack of knowledge, since it was my very first time having fry.

I do intend to trade four of the males (they're swimming around acting like randy teenagers..) to a local pet store in return for a new adult or two.. and naturally when the other fry are big enough they will be traded as well. I like the idea of breeding them for a hobby but I'm concerned about in-breeding and want to get some more diversity. 

Does anyone know what different types of platies are available? Most of the pet stores near me only ever ten to carry the same red wags that I already have..


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## PaulLamb (Nov 15, 2009)

This thread here may be of interest - It shows pictures of some of the Platy varieties. Google images is another good source.


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## guppymonkey (Nov 23, 2009)

Temperature and pH do not effect the ratio of males to females in Platy. It can effect it in cichlids, such as Kribensis, but not in platies. Most of the time when platies or swordtails "switch" sexes its just a late developing male.


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## hXcChic22 (Dec 26, 2009)

I don't know anything about temp or ph... but I do know that all our molly and guppy fry looked like females until they grew up a little and some started showing gonopodium. It's not that they WERE females, it's just that the characteristics take a while to develop.


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## Guest (Mar 8, 2010)

sorry monkey....it does.


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