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Sex ratios and temperature

Discussion in 'Husbandry / Breeding' started by Ttw, Dec 3, 2014.

  1. Ttw

    Ttw Active Member 5 Year Member

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    I am aware of the effect of temperature on sex ratios. However, there seems to be some confusion, maybe just in my mind, about whether the temperature effect is when the eggs are laid or the temperature in which the fry are raised. What is the current thought?
  2. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

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    According to Römer & Beisenherz (1996) sex determination occurs over the first 6 weeks post-spawning. So ideally one should breed and keep the eggs/fry at the preferred temperature for at least 6 weeks. Since it occurs over a long period, one should be able to take eggs/newly freeswimming fry from higher/lower temperatures and raise them at the preferred temperature and still get close the the sex ratio you want. I don't know if this actually works; maybe a good graduate thesis?
  3. Frank_H

    Frank_H Active Member 5 Year Member

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    That's interesting, because in his "Cichlid Atlas", Vol. 1, Römer says that merely the first 25 days after spawning are relevant for sex determination?!
  4. rdrooster

    rdrooster New Member

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    Does ph play a role in determining sex?
  5. wethumbs

    wethumbs Active Member 5 Year Member

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    The 600hrs (25 days) is a simple estimation of his data set. It is not exact at all. His data set was also limited to only a few species. Study the graphs on p.153 and 154 and you will understand (or maybe not).
  6. Frank_H

    Frank_H Active Member 5 Year Member

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    I have studied the graphs and I think I understood them quite well. But this isn't the point here. The point that drew my interest is that Römer himself concludes in the Cichlid Atlas text that the graphs show that the relevant period is 600 hours, whereas the paper Mike has cited seems to say that the period is much longer. Since the Cichlid Atlas is published in 1998, it's safe to assume that Römer knew his paper from 1996 (the german version is even from 1995) and that the conclusions from that paper will probably not be based on better data from more species than the later published text in the Cichlid Atlas. So if this paper says the relevant period is significantly longer than 25 days, my question is simply what is the correct conclusion from his work/data? Of course, normally one would assume that the later one is also the better founded one, but if this isn't the case here, I would be interested why?
    Moreover, the maximum length of the relevent period that one could possibly read from the graphs is imo 850 hours = 36 days. And ths is still much shorter than 60 days.
  7. Mike Wise

    Mike Wise Moderator Staff Member 5 Year Member

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    Personally I don't really care whether it is 24 or 42 days. When in doubt, pick the more conservative (longer) period.:) I keep my breeding tanks (the fish room, actually) at a constant temperature and don't worry about it.
  8. gerald

    gerald Well-Known Member 5 Year Member

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    The sex organs might become differentiated into either testes or ovaries at different ages in different individuals, based on interaction of many different environmental and socially-influenced factors. Anybody who has raised aquarium fish, whether cichlids, livebearers, tetras, rainbows,or other fish, has seen "early-bloomers" and "late-bloomers" that show visible sex characteriistcs at widely different ages, from a few weeks to several months. Presumably the sex determination of the gonads (which must happen before or during the outward changes) can also occur over a prolonged age range. I would follow Mike's advice and go with the longer period. Has Romer or anybody else done any further CONTROLLED experiments on this after the early 1990s work? And do other cichlid groups (e.g. Pelvicachromis & Nanochromis) follow a temperature & age effect pattern similar to Apistos?
  9. Tph

    Tph New Member

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    it seems the study of Romer is the only one for Apisto (kind of strange... or the study had so much impact it became definitive):
    "In the genus Apistogramma (South American Cichlids),
    TSD was demonstrated in many species and thus also seems well
    established, although the evidence gathered so far originates from a
    single study" (Ospina-Alvarrez&Piferrer, 2008)
    see more here:
    http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002837
  10. gerald

    gerald Well-Known Member 5 Year Member

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    Thanks for posting that link. Albert So reported in the Nov-Dec 2012 issue of Cichlidae Communique (Pacific Coast Cichlid Assoc) that his wild-caught pair of Pelv. taeniatus Moliwe produced 3/4 females at 73F, 1/2 females at 79F, and 1/4 females at 85F, with pH 6.5 to 7.0 and conductivity around 150 uS. Sex became apparent externally at about 6 weeks old at 79F; he didn't specify age of sex determination for the higher and lower temps.
  11. rr16

    rr16 Active Member 5 Year Member

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    Did he repeat breeding them at the different temperatures? If each sex ratio at each temperatutre is based on only one spawning then this is evidence of the temperature effect in this particular pair of individuals of this species, but would require further studies and the results should be replicable to ascertain any kind of pattern.

    There are just so many interesting studies that could be done, but need people to do them for free (graduate projects or scientifically-minded hobbyists with fish rooms), or else need money to fund them.
  12. mixmixi

    mixmixi Member

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    This is a very unreliable practice in my opinion. Even if studying a species and concluding by raising the temperature, the number of female decreases, could this be applied for a higher or lower tds? pH? I would tend to not rely on an individual study as a conclusion...
  13. rr16

    rr16 Active Member 5 Year Member

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    I seem to remember reading somewhere that pH or other factors tends to have a correlation with sex ratios too. Again, correlations don't always equal cause, but who knows. No idea where I read it or how reliable it was though.
  14. wethumbs

    wethumbs Active Member 5 Year Member

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    Dr. Romer used Design of Experiments (DOE) for his studies. DOE is widely used in engineering, pharmaceutical, and many other areas of applications. He used 2 factors interactions (temp. and pH) for his experiments with CSS-Statistica statistical software to do the analysis. I personally used a different software (JMP) but the resulting tables, graph, charts are similar. The software is basically a tool, it still requires a 'trained' individual with a certain level of statistical knowledge to interpret the data and come up with a conclusion. I would not be surprised if he got help from someone in the math department when he was working towarded his PhD.

    P.146 of the Cichlid Atlas I shows the interaction plots of 7 different species of Apistos. As the plots indicate, some are influenced by temperature to varying degrees while others are more by pH. It is also interesting to see that at certain temperature, pH interaction on sex determination becomes negligible for some species.
    Last edited: Dec 9, 2014
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  15. rr16

    rr16 Active Member 5 Year Member

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    Ooh, sounds interesting. Perhaps I should invest in this Atlas! I hate statistics, but like diagrams! Maybe I could get a PhD in something like this!
  16. dw1305

    dw1305 Well-Known Member 5 Year Member

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    Hi all,
    I don't know if there are any other published studies, or even if hobbiests have there own data for pH, temperature and sex ratio, but if this data were available it would be possible to conduct a meta analysis on this which would give approximate confidence intervals for the effect of pH and temperature (and their interaction) on gender.

    We use "R" <http://www.r-project.org/> for this sort of work, which has the advantage of being open source soft-ware <http://www.jstatsoft.org/v36/i03/paper>.

    cheers Darrel
  17. BigTom

    BigTom New Member

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  18. dw1305

    dw1305 Well-Known Member 5 Year Member

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    Hi all,
    I can only use it with "Rcmdr" as a GUI, but now I'm addicted.

    Darrel
  19. BigTom

    BigTom New Member

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    It's great once you've got scripts for everything you want to do, but I hate learning new packages. I am terrible at scripting in general however.

    It probably didn't help that the last package I had to learn (rMark) has a manual called 'A Gentle Introduction...' which is 1000+ pages. I guess that isn't really R's fault though.
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  20. wethumbs

    wethumbs Active Member 5 Year Member

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    It reminds me of the RS/1. Personally, I prefer SAS, is like working with MS DOS versus Windows.