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sex ratios

BOB MAJOR

New Member
5 Year Member
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

Moderator
Staff member
5 Year Member
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

Member
5 Year Member
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

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

TCMontium

Active Member
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?
 

gerald

Well-Known Member
5 Year Member
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

Moderator
Staff member
5 Year Member
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).
 
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