1. Hello guest! Are you an Apistogramma enthusiast? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's a great place for Apisto enthusiasts to meet online. Once you join you'll be able to post messages, upload pictures of your fish and tanks and have a great time with other Apisto enthusiasts. Sign up today!

sex ratios

Discussion in 'Apistogramma' started by BOB MAJOR, Aug 23, 2018.

  1. BOB MAJOR

    BOB MAJOR New Member 5 Year Member

    Joined:
    Mar 22, 2013
    Messages:
    20
    Likes Received:
    0
    Trophy Points:
    1
    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.
  2. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

    Joined:
    Mar 16, 2004
    Messages:
    9,573
    Likes Received:
    1,210
    Trophy Points:
    113
    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.
    Ade205, TCMontium and gerald like this.
  3. awth

    awth Member 5 Year Member

    Joined:
    Aug 1, 2006
    Messages:
    125
    Likes Received:
    1
    Trophy Points:
    18
    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?
  4. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

    Joined:
    Mar 16, 2004
    Messages:
    9,573
    Likes Received:
    1,210
    Trophy Points:
    113
    According to Römer & Beisenherz (1996), 26°C/29°F produced 50/50 sex ratio, although pH had some effect on some species.
  5. TCMontium

    TCMontium Active Member

    Joined:
    Jun 4, 2016
    Messages:
    156
    Likes Received:
    25
    Trophy Points:
    28
    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?
  6. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

    Joined:
    Mar 16, 2004
    Messages:
    9,573
    Likes Received:
    1,210
    Trophy Points:
    113
  7. TCMontium

    TCMontium Active Member

    Joined:
    Jun 4, 2016
    Messages:
    156
    Likes Received:
    25
    Trophy Points:
    28
  8. gerald

    gerald Well-Known Member 5 Year Member

    Joined:
    Dec 28, 2006
    Messages:
    1,464
    Likes Received:
    625
    Trophy Points:
    113
    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!
  9. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

    Joined:
    Mar 16, 2004
    Messages:
    9,573
    Likes Received:
    1,210
    Trophy Points:
    113
    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).

Share This Page