What triggers a T to go into premolt?

Methal

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From reading my other post on feeding my Ts, and their growth rate, I would like to spark a discussion on exactly what happens prior to a T going into premolt, and what starts that chain of processes.

I've learned that the availability of food, and how much a T eats.

From this can we assume that when T gets to a certain "fullness" something triggers to start growing a new exoskeleton under the current? (kinda like Cell division cycles)

Or is it more of a continuing developmental process that begins the moment the current exoskeleton hardens?
my line of thinking here is that the new exoskeleton begins to form, regardless of how much the T eats, and once it is developed enough then premolt begins.

Or is it something entirely different?
 

cold blood

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A full abdomen is the #1 trigger....it will happen over a much longer period of time if the t isn't fed well enough, but that shouldn't be happening to captive t's....but a certain amount of food is required.
 

AphonopelmaTX

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From reading my other post on feeding my Ts, and their growth rate, I would like to spark a discussion on exactly what happens prior to a T going into premolt, and what starts that chain of processes.

I've learned that the availability of food, and how much a T eats.

From this can we assume that when T gets to a certain "fullness" something triggers to start growing a new exoskeleton under the current? (kinda like Cell division cycles)

Or is it more of a continuing developmental process that begins the moment the current exoskeleton hardens?
my line of thinking here is that the new exoskeleton begins to form, regardless of how much the T eats, and once it is developed enough then premolt begins.

Or is it something entirely different?
You're on the right track here. First let me state my disdain for the term "premolt". It is so ambiguous that it is hard to determine what someone is referring to when using it. Technically, a spider is in "premolt" as soon as it is done molting (ecdysis). There are so many stages to the formation and shedding of the exoskeleton that "premolt" can encompass any of them except for ecdysis. Though, I think usually it is used to describe the state of the development of the new cuticle to where it can be seen through the old cuticle and behavioral changes are observed. Since you specifically asked what triggers the start of growing a new exoskeleton, I will assume "premolt" is defined as the stage in which the development of the new cuticle (exoskeleton) is formed.

Research has shown that it is the overall health of a spider (this includes tarantulas as well) is what gets the hypo and hyper dermal cells to start producing the new cuticle as well as new muscle fibers, nerve cells, etc. by their respective cells. I've read some mention that hormones may also play a part in this although I couldn't find what hormones exactly or even if that is confirmed. If a spider eats well, is well hydrated, and lives in ideal environmental conditions, the formation of the new cuticle proceeds and the full process of molting continues. If a spider is not well fed, meaning malnourished, then the process of new cuticle development is delayed and the likely hood of problems occurring increases. I have experienced the latter a few times with specimens of Theraphosa blondi. I observed stunted growth, delayed intermolt cycles, and eventual physiological problems that caused its demise as a result of poor nutrition. I have also seen severely deformed T. blondi juveniles as a result of the same thing.

After the new cuticle is formed, the actual process of molting (ecdysis) however is controlled by a hormone called ecdysone. Experiments have shown that during the stage right before and right after ecdysis, the hemolymph contains a much greater quantity of ecdysone than in any other stage of the intermolt process. Further experimentation with this hormone has shown that if a spider is injected with a solution of ecdysone to artificially raise the level of this hormone in the hemolymph, ecdysis can be stimulated prematurely. However, this only works at a stage when the new cuticle has completely formed and ecdysis can be performed. When ecdysone is injected to early in the intermolt process, ecdysis is actually delayed or problems occur resulting in the spider's death. Spiders and other insectivorous arachnids also have an ability to metabolize ecdysone from the prey they consume as a way to prevent it from interfering with their own molting.

For further information, I suggest the book "Biology of Spiders" by Rainer Foelix and to study molting, development, and the ecdysone hormone in general as it applies to all arthropods. Then you can research how spiders differ.
 

Methal

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I was going to start a new thread asking, when I came across this ^ gem.
That right there is perfect =D
 

EulersK

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I was going to start a new thread asking, when I came across this ^ gem.
That right there is perfect =D
But... you were the OP. Did you just make a thread and never check in on it again?
 

Vanessa

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This is extremely interesting.
The only question I have is with regards to limb regeneration. It seems as though they moult more quickly when they need to regenerate a limb. So, how does that factor into the process? How much of those triggers are environmental and how much are they consciously put into motion by the spider itself?
I know that keepers will feed more often when limb have been lost, but I have also witnessed a very quick moult of a wild spider who was missing four of their legs.
Do they consciously speed up the process to aid in limb regeneration?
 

Formerphobe

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Not all amputees push a molt. I've had a few that seemed to take longer in the regeneration cycle than in a normal cycle. One, an A versicolor that I received as a 6 legged sling, seemingly ended up an entire molt cycle behind his sac mates. Somewhere along the line he had an additional molt and matured with an extra molt and nearly a year after his male sac mates. He also matured at a significantly larger size than they.

I acquired a very mature 7 legged G porteri in what appeared to be "premolt". She finally molted about a year later. Her schedule seems to be about every 2.5 years, consistently.

I have an Aphonopelma eutylenum from the 2011 ATS conference. I received her with all appendages intact. She had a bad molt in April 2015 and lost 4 legs. It took her 3 years to molt her first time with me, then about 1 year to the bad molt. She is just now starting to behave "premoltish", which likely means she will molt later this year, or possibly into 2017.
There's often no rhyme nor reason. They molt when they need to.
 
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