The Tarantula molt process, or how to become a virgin again.

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Brachypelma smithi in her old clothes

This would have been a “tarantula bits” post, except I liked the title, so hey.

Last night my Brachypelma smithi, a purchase from a local Petco, molted, and Tom Moran posted up a Grammostola iheringi update where the molt had just occurred with one of his 8-legged cats.
SYNCRONICITY!   heh heh.

I had photo-documented the process with my B. smithi, so I figured I’d post up about the how, what and whyfores with some most excellent shots to illustrate just how Tarantulas “do”.

One of the interesting facets of the exotic pet hobby (not JUST tarantulas) is the molting process. Reptiles shed, as well as snakes, and almost all inverts as well.

[aside: This includes all of the sea-abiding cousins such as this kid here:]

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It is a major difference from the mammalian side of the family tree, and one that I find endlessly fascinating.  Even my tarantulas’ food, the roaches and crickets, molt to increase in size or sexual maturity.

As the title says, “how to become a virgin again”. Tarantulas accomplish this feat of legerdemain every time. When they exit the old clothing, they lose their sex organs, as new ones have grown inside the new suit of clothes. This is a GOOD thing for us Keepers, as it is the most reliable way to sex a specimen. There are other external visual methods, but these require great eyes, patience and oft-times a co-operative tarantula, which, with some species, could be hazardous to both keeper and T.

The sexing process with the old exoskeleton, called the exuvia, is much easier, and with larger specimens, not even a strain on old-fart eyes.  (That’d be me.)

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My Brachypelma smithi exuvia. Circled are the sex organs, and the arrow points to the “spermathecae” which definitively identify the female. Males usually just have a horizontal slit with none of the rest of the gear.

Tarantulas “shed” frequently as spiderlings (slings). This is due to faster growth as the sling is most vulnerable to predation and desiccation. The small slings lack the protective waxy coating that holds up to 99% of their body’s water safe inside. Once the waxy coating is achieved, this reduces the dehydration issue to a bare minimum.  The rapidity of the molting process decreases as they grow older and larger, culminating with young and mature adults that normally molt approximately once a year…except for the males which undergo what is termed an “ultimate molt”.

For an “ultimate molt” male, this is normally a death sentence, but it is also the time to go have lots of adventurous sex, so there is an upside for them. When most genus of tarantula males mature, this “final” molt ushers in some major changes for them physiologically.

Their pedipalps (the front paws, if you will) change and become bulbous. These bulbs, or “boxing gloves” as they are referred to in the hobby, store sperm.  You see, Tarantulas don’t have sex like we do…or I should say quite like we do. The male creates a special web, ejaculates a large quantity of sperm into it, and then loads the pedipalps with the results. These bulbous sperm carrying legs ultimately will use the epigastric furrow (think female tarantula vagina) to insert the sperm.

They also (most species) gain “tibial hooks” on the main front legs. These are used to hold back a female’s fangs and chelicerae while the sex is happening. (Sex just isn’t as good if one is gored before getting things rolling. Heh.)

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The circles are the “boxing glove” pedipalps and the arrow points to one of the tibial hooks.

 

This means he can go wandering about the countryside spreading the loooove to more than one female…if he can survive the encounter, as the female, once satiated, often becomes quite hungry, and she is absolutely NOT averse to eating her sex partner.

Occasionally a male will survive to molt once more beyond the “ultimate molt”, but they aren’t biologically built for this, and a lot of the time the “post-ultimate” molt is a disaster and they die. It isn’t unheard of for a male to survive this, but they become creaky old Granddads, and normally join the choir unseen with Monty Python’s parrot at this stage.

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Two lovers. Male on the left.

For the mature females, the molting process becomes more of a housekeeping chore, or as I like to think of it, a new set of clothes without all the bother of shopping. The female, once mature, will continue living on, sometimes for decades depending upon species. She will be able to raise new kids throughout most of her life.

For the examples that follow, the Brachypelma smithi “Mexican red-knee” female can live over thirty years. Think about this a moment:

A dog MIGHT live 15-20 years. This pet tarantula is something that us older folks would leave in our last will and testament.

One of the handy-dandy other reasons a tarantula will molt is to repair damage. They can and do regenerate lost limbs and such. This is accomplished by molting, and in some cases of severe damage, the molt can be brought on in a hurry.

[Aside]:

While beyond the scope of this post, there some bad things that can happen during a molt, one of which I recently observed with my Grammostola sp. norte “Notyetta”. It is referred to as a ‘wet-molt’. There is only anecdotal information as to the why’s and such, but most of the time, something goes wrong internally and the tarantula, being soft, tears itself apart when leaving the old exoskeleton. Sometimes the process isn’t fatal (as with Notyetta), but there is a slimy wet appearance overall and odd coloration changes. Before and after pics of this issue here:

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Before with normal coloration

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After a “wet molt”

 

And we’re back to the molting process itself.

This is a dangerous time for a tarantula in the wild. The process can be long, arduous, and once complete leaves the T in an extremely vulnerable state for days as they “dry out”. The new set of clothes hasn’t hardened at completion, and takes awhile to become the body armor that it is evolved to be.  The achilles heel for a tarantula is that it doesn’t have blood like we do, or a mammalian circulatory system.  There is no coagulation as they have a substance called hemolymph rather than our hemoglobin. The exoskeleton keeps the everything sealed inside, and if ruptured, the tarantula can rapidly bleed out. The legs are an exception to this as they have valves in the joints which can shut and keep things “inside”…but this isn’t a guarantee for them.

For an excellent breakdown of the spider’s legs and the mechanics involved, I’d recommend this article in the “Infinite Spider” blog by Karen McDonald.

This hazard includes the fangs. Upon molting they are brand new and milky in coloration. Until these turn to a shiny dark color, they are as soft as the body, and can be easily broken off. This is one of those “bad” things as without the fangs, the tarantula would starve most of the time. (There have been reported cases where fangless specimens have been nursed through to a 2nd molt in captivity by feeding pre-killed and sliced open food, but it is rare, and mostly anecdotal.)

In captivity, this whole process of molting is much less dangerous…IF the Keeper leaves the tarantula alone, as well as getting the prey out of the enclosure.  (Many types of feeder insects, crickets in particular, are carnivores and will gladly eat the temporarily soft shelled predator.)

The first part of the process, and one mistaken by new Keepers as “death”, is the flip. The tarantula must push ‘out’ of the old exoskeleton, and it does this by cracking the carapace (the top piece where the eyes are), flipping on their back and then starting the extrication process.

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Brachypelma smithi in the flipped position.

[Aside: I mentioned “eyes”..which isn’t completely accurate. Tarantulas don’t lose their eyes when they molt. What look like eyes are actually just lenses. The optic nerves end at the lenses, traversing down to the brain. When a tarantula molts, not only does it regain its virginity, but it gets a brand new set of shiny eyeglasses (with 8 lenses) as well.]

Once the tarantula is in this position, carapace now cracked, it begins the process of pushing out. While this is going on, it may appear to the observer that nothing is happening, but this isn’t the case. Inside, the animal is moving, pushing and adjusting, as almost every single part of it must be pulled out of the old body through the cephalothorax. The abdomen (opisthosoma) and pedicel (the waist connector between head and abdomen) release when the old abdomen splits.

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Here we can see the process getting fully underway as the opisthosoma (abdomen) has already begun to split.

 

Now things are getting rolling.  Up until this point, it can take the larger tarantulas hours of internal prep work.  Many newer Keepers begin sweating bullets about this point, but here, things are completely out of the human purview, and entirely in the internal spider-realm.

The carapace, now fully released below allows the tarantula an egress point. It splits the old abdomen and begins the serious work of pushing itself out of the old exoskeleton. All of the pictures showing the B. smithi are of my own tarantula doing the job on 9-23-16. The captions describe each shot and what is going on:

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About 1/2 way through the process.

Normally during this endeavor the tarantula pauses, resting, before continuing on.

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Mostly out, the tarantula extricates the legs.

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Looking closely at the top of the picture, you can see the new fangs which are pearly white, nearly translucent.

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Job complete, the tarantula rests beneath the exuvia for a time before flipping back upright.

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One Brachypelma smithi with new clothes…and a virgin…and it’s a GIRL!  🙂

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Turned around showing off.

 

Two different angles of her ‘exuvia’. This is a really nice example as things haven’t gotten twisted up during the process.

So there you have it. There are more bit/n/bobs to this, but as a general guide as to what goes on, that is pretty much how they “do”.

(And yes, I love the youtube show “Interesting facts about the -fill in the blank with different animals-” show.)

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