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Tarantula sexing

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Post Options Post Options   Quote cossor Quote  Post ReplyReply Direct Link To This Post Topic: Tarantula sexing
    Posted: January 18 2006 at 3:55am

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

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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Post Options Post Options   Quote arachnofreak Quote  Post ReplyReply Direct Link To This Post Posted: January 18 2006 at 9:37am
Very nice post and pictures, thanks cossor.
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Post Options Post Options   Quote cacoseraph Quote  Post ReplyReply Direct Link To This Post Posted: January 27 2006 at 6:12pm
this is a smoking hot sexing guide!

those pics are unbelievable!

how did you make them?

also, you don't subscribe to ventral sexing via epiadrous fusilae?

i think v-sexing is very misunderstood and does not lend itself well to the internet (jpeg compression can "erase" EF sometimes). it seems like a lot of ppl assume if you can't see the EF in a single pic then obviously the spider is female... i think that is silly and part of the reason v-sexing is so deprecated in some circles :)
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Post Options Post Options   Quote Brachybaby Quote  Post ReplyReply Direct Link To This Post Posted: January 29 2006 at 8:43pm
wow that is a really useful thread thanks!
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Post Options Post Options   Quote cossor Quote  Post ReplyReply Direct Link To This Post Posted: January 29 2006 at 9:44pm

Thanks , i hadnt seen any sexing guides posted on the net that went into any greater detail than "if it has a flap then its female" followed by some pics with no explanation of what it was you were looking at so i decided to take a stab at it. Its not the best by any means but it does point you in the right direction. The pics were taken just by pointing the camera down the eyepiece of my microscope and taking a picture as normal.

As for ventral sexing its not something i can do very well and im sceptical as to whether anybody can determine the sex correctly all the time using this method especially with smaller spiders so i stick to skin sexing which can be done from the 6th instar up.

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Post Options Post Options   Quote thevez2 Quote  Post ReplyReply Direct Link To This Post Posted: April 16 2006 at 8:00am

Cossor,

Do you know where we can obtain a copy of the Hancock text you reference?

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Post Options Post Options   Quote cossor Quote  Post ReplyReply Direct Link To This Post Posted: April 16 2006 at 9:50am

Yep you can either spend hours searching for a copy online at specialist book sites or just sign up for the BTS sexing diploma course (open to international members as well i believe).

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Post Options Post Options   Quote ancientscout Quote  Post ReplyReply Direct Link To This Post Posted: April 16 2006 at 10:28am

cossor, you did an outstanding job once again and as usual. I am a bit more clear on that now. Perhaps you should start something like spiderboy magazine. It might be a hit and, I'm sure the pinups would go along ways in calming all those male tarantulas in captivity. You did good bud.

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Post Options Post Options   Quote thevez2 Quote  Post ReplyReply Direct Link To This Post Posted: April 17 2006 at 1:12pm

Cossor,

I've seen the sexing course on the BTS website.  I don't have the time to put into it right now.  I'd love to though, eventually I'll get around to it.  Plus it is kind of expensive for those of us who are overseas.

In the mean time, that's what you're here for, right? J/K

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Post Options Post Options   Quote cossor Quote  Post ReplyReply Direct Link To This Post Posted: April 17 2006 at 1:49pm

Just dont ask me to ventrally sex anything

You can get the book here http://www.spiderschool.info/publications.htm

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Post Options Post Options   Quote thevez2 Quote  Post ReplyReply Direct Link To This Post Posted: April 17 2006 at 1:59pm
Thanks for the link cossor, and I wouldn't really trust anything but a cast skin anyway.
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Post Options Post Options   Quote DJ Quote  Post ReplyReply Direct Link To This Post Posted: June 25 2006 at 3:06pm
This thread should help alot of people who dont know much about sexing tarantulas. Thanks cossor.
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Post Options Post Options   Quote jade8531 Quote  Post ReplyReply Direct Link To This Post Posted: July 01 2006 at 3:34pm
Cossor...YOU'RE SO SMART!What would we do without you?Do you mind if I try to copy those pics or that entire guide to my computer for future sexing?Thats the best pics and explanation that I have ever seen and believe me,I have done some looking.I feel completely confident on my sexing of Miss Lucys shed from the pics and info that you gave me when she molted.THanks again....YOU SO SMART!
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Post Options Post Options   Quote cossor Quote  Post ReplyReply Direct Link To This Post Posted: July 02 2006 at 11:04pm
Lol im not really that smart all i did was take a few pics and label them then type out some nonsense i learned from a couple of books. Feel free to copy the guide to your computer if you think it is any use to you.
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Post Options Post Options   Quote ancientscout Quote  Post ReplyReply Direct Link To This Post Posted: July 03 2006 at 10:26am
Nonsense?..possibly but useful nonsense. Sexing is an issue on almost every board. It promotes endless debates as to whether this way or that way works. Frankly, if mygalomorph males would have simply evolved with external parts as most mammals I would think the entire process would have been somewhat easier.
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Post Options Post Options   Quote YouLosePayUp Quote  Post ReplyReply Direct Link To This Post Posted: July 03 2006 at 7:07pm
Originally posted by cossor

As for ventral sexing its not something i can do very well and im sceptical as to whether anybody can determine the sex correctly all the time using this method especially with smaller spiders so i stick to skin sexing which can be done from the 6th instar up.



I believe Rick West started the ventral sexing/EF craze back when he did a demonstration for the BTS(could've been ATS).  Anyway I believe even he said that it isn't 100%, and stated that it would be best to help guide someone while buying a petstore T where the store has no previous molts or idea on the sex of the animal.  It would be interesting to see how many Rick himself has sexed via EF and what percentage were right.
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