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My Endler's tank has been running for about a year now. The ratio of female to male fry is at least 3 to 1, if not higher. Water temp is 77°, pH is 7.0, although it was closer to 7.4 before we moved.

Is this common or has anyone else experienced this? Does it have something to do with temp, pH, or another factor?

Last edited by Theresa_M at 07-Jan-2005 11:19

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There is water at the bottom of the ocean

I think it means they have you well trained, That is you are taking good care of your fish.

My cattle usually have male calves the first time and they have a high birth weight. It is like they want to do it right the first time. Sometimes this can cause a problem with the delivery. Alpha cows in my herd have male calves and younger cows have heifers. An old cow with low status or a really old alpha cow will have heifers.

I guess you wished you put on your boots before you read my post?

max

I do not think it is the temperature. With my guppies are the opposite. I usually get 2males : 1 female. Try warming your temperature. You might get more males that way.

Truelly it is the luck of the draw, same as in humans. I remember thinking that my male fry were stupid, or something......as I was having a lot more females than males...now it is about 50-50...enjoy the fact that they are breeding and all is well for you and your fish...keep watching, maybe as some of the males get old enough to breed you'll find that you have more females...Have Fun!!!

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"I've got a great ambition to die of exhaustion rather than boredom." Thomas Carlyle

I believe a ratio 2f:1m is normal due the guppy having XY&Z chromosomes....

Interestingly, I have guppys in water ph 7.6 hardness 320ppm++, temp 82, and my fry are almost always a ratio of 4:1 males over females.
My sister has guppys at water ph 7.0 hardness 60ppm, temp 82, and her fry are about 3:1 females over males.
Oddly, I suspect the water hardness has a great deal to do with it. At the place I lived before, I had about 50/50 male and female fry, and the water was much much softer.


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This is the first I have heard of that. Tell us about the Z chromosomes? I hear the Y chromosome is longer than the X chromosome.

I have a drop of all female pinks(fortyish). Other drops are about 50/50.

max

I know that it's difficult to hold them upside down, lol, but I swear that mother (mollie) only has females, which suits me fine. I haven't found one male yet, and her oldest litter is approaching two months, about 1.25 inches. maybe the males taste better? Maybe I'll find some later. But after about 50 fry I still can't find a male

Well I want to muddy the water some more. I found the Z chromosome in birds. This article seems to say guppies might be an XY system:

Genetic data indicate that P. reticulatus has an XX/XY system of sex determination
http://meiosis.bionet.nsc.ru/Fishhyb.htm

This article suggests sex determination in at least some fish is more complicated than that:

Bony fishes are a group with an extraordinary variation in sex determination. Environmental sex determination, polygenic sex determination and chromosomal sex determination of the XX/XY or WZ/ZZ type can be found. Three fish species represent the basic steps in sex chromosome evolution. The zebrafish, Danio rerio, has environmental or polygenic sex determination (not clear yet which) and, hence, no sex chromosomes were found. The platyfish, Xiphophorus maculatus has genetically defined sex chromosomes. But in a confirmed XX/XY strain, sex chromosome differentiation could not be detected in synaptonemal complex (SC) bivalents by electron microscopy nor with comparative genomic hybridization (CGH) in mitotic and meiotic chromosomes (though in situ hybridization by Nanda et al., 2000, with a specific repeat probe detected a difference). In contrast, in the guppy, Poecilia reticulata, the acrocentric Y chromosome could be identified cytogenetically. CGH revealed a large distal segment that contained male-specific and should include the sex-determing region plus some Y-specific color genes. The proximal half of the chromosome is similar to the X chromosome, is synapsed with the X chromosome in early pachytene and, hence presumably 'pseudoautosomal'. Differentiation thus is restricted to the distal half of the chromosome while the proximal half is in exchange with the X.

http://www.bioweb.muluebeck.de/RESEARCH/CHROMOSO/ChromStru.html

max

http://www.bioweb.mu-luebeck.de/RESEARCH/CHROMOSO/ChromStru.html

Sorry, There was a problem with the hyphon.

max