sex determination

[Patrick Guhmann]

Hello,

I have some questions to the specialists and breeders. Can you tell me something about the sex determination in Parosphromenus. What influences it (for example temperature, pH are known as factors in Apitogramma) and at what time of the development? Have you recognized differences between several species?

Greetings
Patrick

[Patrick Guhmann]

No answer, OK perhaps it is not clear what I want to ask. I try it again 😉

Are factors like pH, temperature, age of the parents…known that influences the sex of the fry? At what point of the Paro life is the decission done if the fish is a male or a female? Are we able to influence the sex ratio of the fry?

Greetings
Patrick

[Peter Finke]

Patrick, excuse me that I did not reply to your questions.
Yes, you are right, contrary to the sex determination in mammmals or most birds in fish or amphibians this decision is not taken in the moment of the fertilization of the egg but in the days and even weeks to come by the influence of environmental factors. We know of the potentially decisive role of temperature, pH and even the quantity of humine substances. I cannot tell you of an exact duration of the period before the decision is taken, but experiments show that it could be rather a long period of several weeks mostly. Quite often breeders complain of whole clutches developing to males or females, and it is most likely that they have put the foundations for that by themselves by a low or high pH, a low or high degree of humine substances or a low or high temperature.
We know of no differences between the Parosphromenus species but there maybe important differences between fish of very different categories.
You can find many additional information in the internet.

[Bernd Bussler]

Also ich züchte nun schon einige Jahre Paros und es kommt immer einmal vor das eine Nachzucht mehr Männchen oder mehr Weibchen hervorbringt, doch meist ist das Geschlechterverhältnis recht ausgeglichen. Wichtiger ist doch die Tiere zum ablaichen zu bewegen und die Jungtiere groß zu bekommen. Ich hätte kein Interesse nur Männchen oder nur Weibchen zu züchten. Bei Fischen die viele Eier legen mag ich da noch einen Sinn sehen, aber bei der geringen Eizahl bei Paro´s loht sich der Aufwand sicher nicht.

[Peter Finke]

Dear Bernd, the problem is not to produce one sex only but to prevent that. I remember that somebody complained that he had about fifty offspring of nagyi but all females. Unfortunately we are unable to give exact borderlines for temperature, acidity or humine concentration. The Most probable reason is that these factors form a joint system and one cannot view each of these separately. Therefore it is impossible to say e.g. “until 25 degrees Celsius males, above females.” I am sorry but it is a bit more difficult. So it is possible that one breeder with low temperatures and a pH near the neutral point has a majority of males, whereas his colleague with high temperatures and very low pH has the same result, but with other configurations of that values we get a different picture

[Patrick Guhmann]

Thank you Peter and Bernd!

[Benjamin Wilden]

Hello

as I said in an other place, my problem was and is that a lot of my young where male. In some cases every young was male.

I tried a lot of different parameter like pH, humidacid, temperature and planting. Nothing changed.

Someone asked me at the IGL meeting about hormone in plastics, but I have no plastic in the tanks…

Maybe it is just fate.

Bennie

[Peter Finke]

Bennie, did you have great numbers of offspring?
Most breeders engage in extensive breeding, i.e. small numbers off offspring. And it is a matter of numbers, of course. If you have five young, the distribution of sex-ratio is insignificant. If its fifty, the thing gets interesting.

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