Skewed sex ratios.. a theory

[stormhawk]

I am inclined to think that at times, skewed sex ratios, at least in killies, can be attributed to perhaps minute amounts of oestrogen in the tap water or aged water we use for our fishes.

http://www.arofanatics.com/forums/sh...d.php?t=341755

This thread on Arofanatics by BettaFillet from 2008 is quite interesting.

Right now, the larger of the 2 female "flagellatus" is showing signs of being a male! It's starting to develop the distinct pattern in the dorsal and anal fin, plus it does not seem to have the black blotches typically present on females of the flavicaudatus group.

[SirBest]

I was once told by a Thailand betta breeder that raising fries in acidic water will yield a higher percentage of females whereas raising the fries in alkaline water would yield higher percentage of males. I dont really know whether such statements made by this breeder makes any sense but I do know that on my past trips to Rayong, when I was hunting for show bettas, I saw practically most betta breeders would house their fries to juvenile stage bettas in concrete round ponds. Within each pond, there is no traces of any ketapang leaves being used. Purely water lettuce or duck weed to act as a shelter to provide shade for the bettas from the hot sun.

[Mystikboy]

I know for a fact that acidity affects gender in offsprings

[RonWill]

Interesting... wondering if incubation temperature during embryol development has an influence on sex skew as well. *thinking about reptile eggs...*

[stormhawk]

Temperature has a role to play too, but I am more concerned with the possible presence of unwanted hormones in our water supply, if any. The tables given by the PUB do not indicate this however.

[icefire]

I know for a fact that acidity affects gender in offsprings

hmm is it possible? really doubt it and would you be kind enough to point me to resources that explain this fact as i thought that gender is due to genes.... not very good in genetics so please point me in the right direction thank you!

[Mystikboy]

http://m.infobarrel.com/How_Can_Wate...a_Fish_Breeder

There is actually quite a lot of paper on this. A quick google yielded the above (:

[SirBest]

Temperature has a role to play too, but I am more concerned with the possible presence of unwanted hormones in our water supply, if any. The tables given by the PUB do not indicate this however.

I dont think the Authorities would want to stick their necks on the chopping board and begin the series of explanation of why this and that. But rather I would see this area as a good field for hobbyist to come in together and share their temperature and water parameters while incubating the eggs and going all the way through the fishes' adulthood. I am aware that such sharing of information might not prove any substantial evidence to support any claims but at least it can point to a proper direction as to how to prevent skewed sex ratios.

[stormhawk]

As consumers, it is our right to know what else is present in our tap water supply aside from what is already listed. A search on Google will give references to the effect of this hormone on animals and humans. While it may not pose a direct threat to humans in very low concentrations, it will affect our fish one way or another.

http://news.bbc.co.uk/2/hi/science/nature/49613.stm

As for temperature, information is present online for certain groups of killies, with respect to incubation times.

http://www.proyectonothobranchius.net/ <-- scrolling down this site will give a notho breeder a rough indication of incubation period at a temperature of 24-25 ºC.

Since our regular room temperature here is higher than that, shaving off a week or two from the given periods is applicable in most cases. For SAAs, the book by Dr Roger Brousseau contains a table with incubation periods. Most plant spawners typically have an incubation period of 1-2 weeks in water, at least in the case of Aphyosemion australe kept in local conditions. An entry on this by timebomb is given here:

http://www.killies.com/Incubating2.htm

[Shi Xuan]

I was once told by a Thailand betta breeder that raising fries in acidic water will yield a higher percentage of females whereas raising the fries in alkaline water would yield higher percentage of males. I dont really know whether such statements made by this breeder makes any sense but I do know that on my past trips to Rayong, when I was hunting for show bettas, I saw practically most betta breeders would house their fries to juvenile stage bettas in concrete round ponds. Within each pond, there is no traces of any ketapang leaves being used. Purely water lettuce or duck weed to act as a shelter to provide shade for the bettas from the hot sun.

I think this information works very well for the ex-Rivulus genus. I have three aff. cryptocallus fry out of a packet of peat a while ago and I'm worried I might have an all male group.

[stormhawk]

Shi Xuan, try raising them in neutral to slightly alkaline water. I raised some tenuis fry in alkaline water and got a decent sex ratio.

[Shi Xuan]

I'm raising them in neutral water and they are about 1.5-2cm now.

[stormhawk]

That's good. My tenuis started sexing out around 2.5 - 3 cm or so. Since cryptocallus gets bigger I figure you'll see them sex out around 3 - 4 cm or so.

[SirBest]

@stormhawk: Able to share pictures of the species of kilifishes that you had mentioned? I am looking forward to that.

[stormhawk]

The tenuis? This is an old thread I posted back in 2005:

http://www.aquaticquotient.com/forum...Rio-Papaloapan

The species is now known as Cynodonichthys tenuis. The survivor that I had eventually turned out to be a male.

http://www.aik.it/assets/galleries/534/rivu_tenuis.jpg

This is how they typically look like. Photo is by Fernando Guerreiro via the AIK website. There are variations of this species.

http://www.aquabid.com/cgi-bin/aucti...ishe1327827282

This closed auction link shows a representative picture of Shi Xuan's fish. The one pictured is probably the wild caught male.