Sexing a tarantula

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6 years 9 months ago - 6 years 8 months ago #18753 by That Cossor guy
Mods feel free to incorporate this into the stickied sexing guide if you wish.

I finally got around to updating the sexing guide i did on another forum so i thought i might as well post it here as well while i was at it.

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.



FEMALE ANATOMY


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 later join together as the spider gets older. The spermathecae is lined with cuticle and is there for 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 how ever two 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. It is also only found on females and is believed to be the area where the sperm and the eggs mix before being deposited into the egg sack .


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.



Fused spermathecae



another example of paired spermathecae


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


MALE ANATOMY



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.




Close up of gonopore


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


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.


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.


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.


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

Some useful tools


Hope this is of some help , for more information on sexing then read Sex determination of immature theraphosid spiders from their cast skins by Kathleen and John Hancock or join the BTS and enroll in the tarantula sexing course if available.



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Last Edit: 6 years 8 months ago by That Cossor guy.

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6 years 9 months ago - 6 years 9 months ago #18770 by That Cossor guy
Hopefully this thread will prove more interesting than bickering about spelling and correct terminology.



Want to know a lot more about tarantulas? Then click ME
Want to be a tarantula geek? Then click ME
Last Edit: 6 years 9 months ago by Fuzzy Bear.
The following user(s) said Thank You: Dimitri Kambas

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6 years 9 months ago #18792 by Private
Thanks Duke and Scarab for your sexing posts.

I have seen these pics a few times on other forums and websites however they don't show the start to finish of sexing a T. My earlier sexing request post was in fact the inner ocular as was pointed out. I have 15 T's from 1.5cm - 15cm. I now know what I was doing wrong with the sexing however that still dose not change Dukes slightly ambiguous post above (found on many T websites) for noobs to the T game when Sexing T's.

Basically what should be shown is the A-Z of sexing a T from the tools used to the pics of the shriveled exuvium to the pointing out areas of interest and areas of possible error to the hydrating and so on….

Possibly a fifteen step detailed guide (I don’t know) on how to sex a T. Extreme close up pics can confuse one as many parts look the same...
Case in point is that close up pic that was posted a few months ago on the forum - Win a Tarantula - guess what part of the T the pic is from...
www.tarantulas.co.za/forum/tarantula-gen...8496-win-a-tarantula

I'm here to offer advice on what I know...
I'm here to seek advice on what I don't know...
I'm not here to get into forum politics so please don't condemn or apologise to me...
Please leave me alone...
Why are you here!

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6 years 9 months ago #18794 by That Cossor guy
IcarusZulu wrote:

Basically what should be shown is the A-Z of sexing a T from the tools used to the pics of the shriveled exuvium to the pointing out areas of interest and areas of possible error to the hydrating and so on….


Are we looking at the same post here? It shows how to prepare the skin, the tools, the area to look at and an explanation of what you should be looking for. I really don't know how i can make it any more obvious. Obviously in your case though i have some how failed so if you can explain to me how it is an ambigous post then i would be very grateful.



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6 years 9 months ago #18818 by BiG DoG
Thanks Duke, I saw this on another site quite a while back I think 2 years back if I'm not mistaken, when I wanted to start sexing my tarantulas and it helped me a lot. haven't miss sexed a tarantula till this date, I'm sure this will help some of the new comers :)

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6 years 9 months ago #18820 by Schalk du Plessis
Clears some confusion up for me.
Thanks Duke.

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