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Male vs Female heavy species

Discussion in 'Tarantula Chat' started by msmagsie, Aug 5, 2018.

  1. msmagsie

    msmagsie Arachnopeon

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    There was recently a post about a certain species being particularly male-heavy. I've heard of a few different species tending to produce more males than females.

    What are your experiences? If you've raised several slings of a particular species, how many did you raise, and how many ended up being female?

    I'm particularly curious about Brachypelma Albiceps and Grammostola Pulchra, since I've read they are both somewhat hard to breed, and tend to be a bit pricey.
     
  2. starnaito

    starnaito Arachnosquire

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    I don't have an answer, but I'm curious about this too. I have a male and female B. albiceps that I'm hoping to pair in the near future. I'm wondering what in particular makes them difficult to breed. Is it just a matter of availability (i.e. hard to find a mature male)?
     
  3. viper69

    viper69 ArachnoGod Old Timer

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    What mystery species are you referring to?

    I'd be surprised if anyone (I've yet to hear/read of anyone) has kept an ENTIRE sac of ANY species and kept track of the gender distribution. This would have to be done for more than sac too in order to be relevant.

    If someone hasn't done this, anything they tell you is not based in data.
     
    • Agree Agree x 1
  4. starnaito

    starnaito Arachnosquire

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    I think the question is for people who have kept several slings of the same species, not the entire sac, and what the female to male ratio is based on that quantity.
     
  5. viper69

    viper69 ArachnoGod Old Timer

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    You could be correct. However, I will let the OP weigh in, as we cannot read minds. If they are asking about slings as you suggest, then such information is absolutely meaningless, and provides zero value.
     
  6. msmagsie

    msmagsie Arachnopeon

    You are correct, Starnaito. I was referring to slings. Although, I'd be curious about gender distribution among egg sacs as well.

    I've read about G. Pulchra being particularly difficult to breed. In searching breed reports here and the few blogs I've come across, it seems that many pairings have been unsuccessful. Granted, I've never bred anything before, so I'm not sure what success rate is normal. I assume it varies by species. As far as B. Albiceps, I haven't come across more than one or two breed reports, so I have no idea what's going on there. I have noticed B. Albiceps seems to be slightly harder to find than other species. Not that they're not out there, but there seems to be more B. Albopilosum or B. Hamorii available on the market.

    Viper69, the mystery species I was referring to is Ornithoctoninae sp. Hatihati. This post is what got me wondering in the first place.
     
  7. viper69

    viper69 ArachnoGod Old Timer

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    As I mentioned, the gender info on sling along is meaningless. If you want to know why, just ask. Sac gender is the only meaningful info.
     
  8. Minty

    Minty Previously mmcg Arachnosupporter

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    I’ve red that Lapropelma violaceopes tend to have more males than females, but I’m not sure.
     
  9. viper69

    viper69 ArachnoGod Old Timer

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    No data on that either or any other species that we know of.
     
    • Agree Agree x 1
  10. dangerforceidle

    dangerforceidle Arachnobaron Active Member

    Biologically, the split between sex should be 50/50. Sex in spiders is determined in a similar manner to sex in humans, by sex chromosomes. Whereas a human female has two "X" chromosomes, and a human male has an X and a Y chromosome, female spiders have XnXn and males have Xn0. There is variation in the number of X chromosomes that a species has, but a female embryo will have two copies of each X chromosome, and a male embryo will have a single copy of each X chromosome.

    There could exist XX for female and X0 for male, but there could be X1X1X2X2 for female, and X1X20 for male.

    This link talks about karyotypes, and this one goes into more in depth analysis -- note, the latter will prompt a download for a PDF. You can find the same URL by searching Google Scholar for "theraphosidae sex determination" and it's the third link titled "Sex chromosomes and meiosis in spiders: a review" authored by D Araujo and MC Schneider et al..

    From the second article, the identified theraphosid karyotypes are X1X20 and X1X2X3X40.

    There may be other factors at play with development that leads to an inbalance in sex. Perhaps there is something on an X chromosome that causes higher termination in female embryos, leading to a 'male heavy' species, for example. That much we don't really know. For all intents and purposes, however, we should probably expect an approximate 50/50 ratio of male and female individuals from a single sac.
     
  11. cold blood

    cold blood Moderator Staff Member

    But it isn't


    Even in humans its a 51/49 split.
     
  12. Zepmaster

    Zepmaster Arachnopeon

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    I think they are all male heavy, but that may be simply because i haven't had the best luck with my slings only one has turned out female out of 6. :depressed:

    maybe its just me though i also have 6 sons no girls maybe my sheer manliness rubs off on all nearby entities shifting the balance to 90/10 :troll:
     
  13. dangerforceidle

    dangerforceidle Arachnobaron Active Member

    See my last paragraph.
     
  14. Ultum4Spiderz

    Ultum4Spiderz Arachnoking Active Member

    Wonder what it was in China during one child law I heard there’s millions more men there.