Why does the abdomen of a T increase in size in premolt?

[KnifingPanda]

Hi guys,

I need some scientific input. When tarantula slings and juveniles approach their molt and the premolt stages have set in, why do their abdomens swell up and resemble a grape that's about to pop?

Does anyone have an explanations? Or is that just one of natures mysteries?

 

[lalberts9310]

I don't know how accurate this is or if this is true, so anyone can correct me if I'm wrong. But i heard this is due to fluid build-up to make it easier for the T to shed their old exo.

 

[EulersK]

While this may be happening, I can't say that I've experienced this. They just get much darker and sometimes shiny - sure, they look like they're about to pop, but I wouldn't say that they're any bigger.

 

[viper69]

While this may be happening, I can't say that I've experienced this. They just get much darker and sometimes shiny - sure, they look like they're about to pop, but I wouldn't say that they're any bigger.

You don't notice the decrease in size of the abdomen after the molt? All of the Ts I've owned demonstrate an increase in abdomen size over time as they approach a molt. My I mira right now is massive, it's going to molt at some point soon. I may misunderstand your meaning.

 

[cold blood]

Their abdomen size increase is directly related to the food the t has taken in....full ts molt.

 

[ratluvr76]

Their abdomen size increase is directly related to the food the t has taken in....full ts molt.

I thought I read a reply by Poec at one time or another about the fluid building up between the new exo and the old exo in heavy pre-molt stages. Maybe I was misunderstanding it? Or is it not enough to show the slight increase in size...? not arguing, just trying to clarify.

 

[AntikInsomniak]

Underneath the exoskeleton (exocuticle) that is about to be shed, they are building a secondary layer. This new cuticle is wrinkled with convolusions, similar to a brain or "pruney fingers", and does explain some of the growth of the abdomen during the midstage of premolting. During molting, this wrinkled new shell will allow the inner organs to swell with fluid, and expand to no longer be wrinkled. So, it balloons. This is what causes the opisthosoma (abdomen) to split, along with an increase in hemolymph pressure.
The blackening that you see on your tarantula/spider is the old cuticle basically separating from the new cuticle (which has now developed black hairs of its own). There is a liquid in this intercuticle/exuvial space called the exuvial liquid. It's believed that this aides in basically lubricating the new cuticle from the exuvium.

Tl;dr - It's a buildup of fluids and the creation of a new shell. It basically builds in pressure until the spider is ready to molt. At this point blood pressure increases, finally splitting the abdomen open, and from there the rest is pretty simple.

I hope this answers your question...

Edited due to grammar

 

[SpiderDad61]

It's not just pre molt feeding that gets abdomens so large. Nine stop eating for a good while, and their abdomens continue to grow larger. It's the seperation between exo's and the fluid build up between them that makes the abdomens to big

 

[AphonopelmaTX]

I can't say I've ever seen a noticable size increase in the abdomen before molting occurs either.

 

[viper69]

I can't say I've ever seen a noticable size increase in the abdomen before molting occurs either.

Really, I'm shocked. I wish I had taken pics of my I mira for example from the time it molted till now. People would see the size increase easily. The same is true for all my Ts, even my slender Avic males.

 

[AntikInsomniak]

Really, I'm shocked. I wish I had taken pics of my I mira for example from the time it molted till now. People would see the size increase easily. The same is true for all my Ts, even my slender Avic males.

With a sling, it's more noticeable than on adults. It's a surface area issue. With a fast growing sling, it is relatively easy to notice. With a juvenile Aphonopelma or Grammostola, finding a noticeable size increase becomes hard, due to how long the spider sits in premolt.

 

[viper69]

With a sling, it's more noticeable than on adults. It's a surface area issue. With a fast growing sling, it is relatively easy to notice. With a juvenile Aphonopelma or Grammostola, finding a noticeable size increase becomes hard, due to how long the spider sits in premolt.

I notice it on all my AFs. Including my AF B albo, AF emilia, GBB and my AF G pulchripes. It's incredibly easy to spot for me. I've raised them all from sling to adulthood, and there's never been a time when I couldn't notice the size increase

 

[AntikInsomniak]

I notice it on all my AFs. Including my AF B albo, AF emilia, GBB and my AF G pulchripes. It's incredibly easy to spot for me. I've raised them all from sling to adulthood, and there's never been a time when I couldn't notice the size increase

That's good that you still notice. I was not claiming it is impossible to see, just that it becomes less apparent as it grows. With a sling, it's shockingly apparent, but with an adult, it doesn't stand out a obvious. Again, not claiming it isn't noticeable. I notice it too, with most if not all of my spiders.

 

[EulersK]

You don't notice the decrease in size of the abdomen after the molt? All of the Ts I've owned demonstrate an increase in abdomen size over time as they approach a molt. My I mira right now is massive, it's going to molt at some point soon. I may misunderstand your meaning.

No, I mean that I don't notice the abdomen getting bigger leading up to a molt. Of course there is a dramatic difference in size after the molt is complete.

 

[viper69]

No, I mean that I don't notice the abdomen getting bigger leading up to a molt. Of course there is a dramatic difference in size after the molt is complete.

Ah gotcha. I'm surprised some people don't seem to notice the size increase, even in adults from time of post molt to the actual molt.