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How to sex your tarantula

Discussion in 'General Tarantula Discussion' started by plessey, Nov 29, 2012.

  1. plessey

    plessey Active Member 3 Year Member

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    The only real accurate way to sex a tarantula is by examining the epigynal area located between the anterior book lungs of the tarantulas shed skin but to do this you must first know what you are looking for.

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    FEMALE ANATOMY

    [​IMG]
    This is a picture of the female sex organs located between the anterior book lungs (top pair).

    The spermathecae: Only present in females these are the sacks where the males sperm is stored and come in a variety of shapes and sizes depending on the species. They can either be a paired structure (as shown in the pic) or a fused structure (usually a singular dome or tombstone shape) and branch off from the uterus externus. Fused spermathecae will start off as a pair and join together over the first few moults. The spermathecae is lined with cuticle and is therefor shed along with the rest of the old skin. Because of this any sperm that has been stored in the spermathecae will be lost after a moult in effect making the female virginal again. There are however two known species in which the females do not possess spermathecae and instead store the sperm in pores in the uterus internus. These are Sickius longibulbi and Encyocratella olivacea.

    The uterus externus: Only found in females, this is a transparent tube of skin that connects to the uterus internus at one end and opens out to the gonoslit at the other end. The uterus externus is lined with cuticle like the spermathecae and is the only part of the uterus shed along with the rest of the old skin. It is the first point where the sperm and the eggs come into contact and is the most important feature in determining the sex of a tarantula from its shed skin.

    The bursa copulatrix: This is the lower alcove that is formed below the spermathecae and the uterus externus. Again it is also only found in females and is believed to be the area where the sperm and the eggs mix before being deposited into the egg sack .

    [​IMG]
    This drawing shows how all the parts connect with the organs that are not shed during a moult.

    A brief description of other features mentioned -

    Uterus internus. A short section of tube that connects to the uterus externus at one end and to the oviducts at the other. This along with the oviduct and ovaries is not shed.

    Oviduct. Two tubes that lead to the overies.

    Ovaries. The female reproductive organs that produce eggs (oocytes)

    Slit sensilla. These are internal stress receptors that sense any stresses on the spiders exoskeleton.

    Arthordial membrane. These are muscle attachments that define the left and right hand sides of the epigynum.

    Gonoslit. This is the opening to the females sexual organs.

    [​IMG]
    Fused spermathecae

    [​IMG]
    another example of paired spermathecae

    [​IMG]
    Encyocratella olivacea - note that although there is no spermathecae there is still a uterus externus and bursa copulatrix.


    MALE ANATOMY

    [​IMG]

    The gonopore. This is the opening in the centre of a males epigastric furrow that leads to the testes. The testes are 2 long coiled tubes that produce sperm and also act as sperm ducts.

    Accessory organs. Also known as accessory glands , epigastric organs or epigastric glands. The exact function of these organs is unknown but they are said to produce an adhesive liquid that helps the sperm droplet stick to the sperm web. They can be very prominent in some species such as Brachypelma vagans and are often mistaken for paired spermathecae. These accessory glands are wider at the apex than at the base and usually look tree or mushroom shaped as opposed to spermathecae which are wider at the base than at the apex. Of course there are a few exceptions to the rule such as Poecilotheria species and Aphonopelma chalcodes for example where the male accessory glands are wider at the base than at the apex.

    [​IMG]

    [​IMG]
    Close up of gonopore

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    You can see the male accessory organs marked in green here and the lips of the gonopore circled in red.

    [​IMG]
    Pic of male accessory organs from a Poecilotheria regalis notice they are wider at the base than at the apex.


    PREPARING THE SKIN
    Unless you have just retrieved the skin from a freshly moulted spider then the skin will be very dry and brittle making any attempt to sex it almost impossible. The most common method to moisten the skin and make it pliable again is to soak it in water with a drop of washing up liquid however i find it is much easier just to give the skin a good spray with a mister for a few seconds.
    [​IMG]

    Once the skin is pliable take hold of the abdomen skin where it joins the carapace and gently pull down on it so that the skin unwinds then cut off the excess skin below the posterior book lungs.
    [​IMG]

    Next take a needle and run it down the abdomen skin from the pedicel (where the abdomen joins the cephalothorax) to the posterior book lungs and carefully open up the skin.
    [​IMG]

    The skin is now ready to be sexed. Some large spiders can be sexed with the naked eye but most will need some kind of magnification. For most adult spiders anything from x2 - x20 will do and this can be achieved by using hand held lenses or jewellers loupes. For sub adults and large juveniles a higher magnification of x20 - x40 is needed and for this you will need a microscope. Finally for sexing spiderlings you will need an even higher magnification of x40 - x80.

    Hope this has been of some help, for more information on sexing tarantulas read Sex determination of immature theraphosid spiders from their cast skins by Kathleen and John Hancock.
  2. Nada

    Nada Moderator 1,000+ Post Club

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    Awesome post. :D
    Bast likes this.
  3. DalilahBlue

    DalilahBlue Moderator 1,000+ Post Club

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    Wow Plessey. I am in awe.
    Bast likes this.
  4. harleyqueen

    harleyqueen Well-Known Member

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    Brilliant.
    Bast likes this.
  5. plessey

    plessey Active Member 3 Year Member

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    Thanks. It's an old post I first did nearly 7 years ago but I don't think I've seen one that has improved on it yet.
    Bast likes this.
  6. john m shires

    john m shires Member

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    very informative
    Bast likes this.
  7. Kurt Nelson

    Kurt Nelson Active Member

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    This should be stickied.
  8. Scoolman

    Scoolman Well-Known Member 3 Year Member 1,000+ Post Club

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    You're cossor?
    Such a small world.
  9. plessey

    plessey Active Member 3 Year Member

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    It's a small hobby. It's not like you can copy and paste someone elses posts from another forum and claim you have permission to do so from the OP without getting caught out. You know what I mean? ;)
  10. pennpets

    pennpets New Member

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    Incredible post! Now I have another use for my loupe besides looking at my coins. Thank you for the information!
    Dratznkg likes this.
  11. TheGreatWhiteKoos

    TheGreatWhiteKoos Active Member

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    Great post...I"ll be sexing some of my T's very soon now.

    Thanx a mil
  12. khatchet

    khatchet Well-Known Member 3 Year Member

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    thanks you I was never told how to sex a tarantula this way.
  13. sinder

    sinder New Member

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    didnt understand. what im Looking for to see if my g rosea is a female or Male?
  14. psawneo1

    psawneo1 New Member

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    Good job-great post. I should have 3 molts coming soon so I can try to sex them
  15. ryan johnson

    ryan johnson Member

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    Is that a molt??
  16. Gavin van den Berg

    Gavin van den Berg Active Member

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    This is very informative.
    I'll be having a molt or two pretty soon so will attempt to determine the sex of my T's for the first time.
    I'm very excited at this prospect.
  17. amberkinn

    amberkinn New Member

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    This is an awesome post, can't wait until my next molt. When I saw the image of the needle holding open the tarantula's sex organ, though, I thought "Next, your agitated tarantula will flick hairs into your eyeball. But don't worry, if this doesn't agitate your skin or eye quite enough he OR she may or may not decide to bite. But it is all for the good of knowing whether Charlotte is actually a Charles."
    Dratznkg likes this.
  18. HungryGhost

    HungryGhost Well-Known Member

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    That's not the tarantula, that's the shed skin.
  19. amberkinn

    amberkinn New Member

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    .
    Last edited: Aug 2, 2014
  20. foritxxar

    foritxxar Member

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    Excellent! Can't wait for my T's first molt with me. I'll just sneak the skin onto my old university and use an unguarded microscope... haha
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