sex ratios

[BOB MAJOR]

Is sex ratio determined by temperature of egg development in all apisto species? I get lots of females in cooler temps with caucatoides. I was wondering if apistos thru out their range from northern Columbia and Venezuela to the extreme in southern Bolivia ,Uruguay etc all have the same triggers in sex determination.

 

[Mike Wise]

No it varies with species although most are similar. You should read "Environmental determination of sex in Apistogramma (Cichlidae) and two other freshwater fishes (Teleostei) by Römer & Beisenherz (1996). Also Römer's micro habitat study on apistos in the wild showed that dominant females chose breeding territories at temperatures that resulted in 50/50 sex ratios, while less dominant females were left to breed in warmer/shallower and cooler/deeper micro habitats. It's a very interesting paper, but published only in a German monograph.

 

[awth]

From my previous experience, cooler temp (below 26C) does produce more female. And I forgot where I read this, 26C is the ideal temp to get 50/50 sex ratio.

Hello Mike, I would like to read this articles. May I ask, does it said at what temp is the ideal to get 50/50 sex ratio?

 

[Mike Wise]

According to Römer & Beisenherz (1996), 26°C/29°F produced 50/50 sex ratio, although pH had some effect on some species.

 

[TCMontium]

No it varies with species although most are similar. You should read "Environmental determination of sex in Apistogramma (Cichlidae) and two other freshwater fishes (Teleostei) by Römer & Beisenherz (1996). Also Römer's micro habitat study on apistos in the wild showed that dominant females chose breeding territories at temperatures that resulted in 50/50 sex ratios, while less dominant females were left to breed in warmer/shallower and cooler/deeper micro habitats. It's a very interesting paper, but published only in a German monograph.

I can read german and once searched for that monograph but couldn’t find it on the internet. Would you happen to know where I can read it? Only as physical copy or are there electronic copies in some websites too?

 

[Mike Wise]

Try: https://docslide.net/documents/envi...on-of-sex-in-apistogrammai-cichlidae-and.html. Sorry, but this is the English version.

 

[TCMontium]

Try: https://docslide.net/documents/envi...on-of-sex-in-apistogrammai-cichlidae-and.html. Sorry, but this is the English version.

No problem, English works just fine as well. Thanks.
I believe these results are also shown in the Cichlid Atlas Vol. 1 by Uwe Römer, but I have to check again to see if the species, ratios and dates etc. are the same.

 

[gerald]

Thanks for the link Mike -- glad to finally have that whole article, rather than just a summary of the findings, Wow, what a monumental research project! 37 Apisto species x 9 different treatments (3 temps, 3 pH's) plus all those fry transfers at various ages into different pH and temp combinations. And then throwing out data from any spawning where > 10% of fry died, to eliminate bias due to sex-dependent mortality. That's a phenomenal accomplishment to raise THAT many spawns with > 90% survival to sexable age. How many years did they spend doing all this? Also BIG THANKS to DOCSLIDE for making this classic paper available for download without a pay wall!

 

[Mike Wise]

It was Römer's PhD dissertation, so several years. I never asked him how long, but he did say that he had a lot of help from Dr. Beisenherz' research assistants (read: graduate and undergraduate students).