The Matoran Spheres used by Teridax in the 2004 story have always had some aspect of mystery to them; Where did he get them? How do they work?
But the biggest mystery has been their inconsistency: Teridax’s Plan required the Matoran to be in the Spheres for so long that he required the Vahi to speed up the process, yet the Matoran of Mata Nui lost their memories and shrunk after being in the Spheres for only a few weeks. And even more contradicting is the fact that Turaga Dume was in his Sphere for around 18 months, yet suffered no apparent effects.
So it got me thinking: What if it wasn’t the Spheres at all?
This theory is the culmination of a couple separate theories that I have shared (and some that I haven’t) over the last few months.
First, we look at the regenerative properties of organic protodermis:
Although the exact mechanisms are unknown, it is a canon fact that organic protodermis can regenerate. This process is not just limited to healing pre-existing damaged protodermis, either; the Toa Mata were shown to completely regenerate missing muscle.
This new protodermis has to come from somewhere. And for that, I turn to a brand new theory of mine:
According to this portion of the theory, the “water” in the Matoran Universe is in fact a slurry of regular water and protodermis. If a Matoran were to ingest this liquid protodermis, it would give their body the protodermis necessary to regenerate missing or damaged muscle tissue.
This also draws a great parallel to the real-world engineering use of slurries, to transport solid material where it needs to go through a pipeline.
With these theories in place, we can create an alternate explanation for the deterioration of the Matoran on Mata Nui: without protodermis in the natural water around Mata Nui, the Matoran would eventually become unable to regenerate even day-to-day wear and tear.
Perhaps, as an emergency measure, their cells would leech protodermis from their armour, in order to keep a balance of muscle to armour, but even that source would eventually reach a minimum balance.
This also explains the memory loss: although the exact structure of Matoran Universe brains is unknown, they likely rely on the repetitive strengthening of memory connections. “Neurons”, if you will. Without protodermis, these connections couldn’t be formed, and old connections might be broken down to reuse the protodermis for new ones.
This “gradual deterioration” theory actually finds support from official canon:
If it took “many years” for the deterioration to occur, that would explain why Dume was unaffected.
But, more importantly, it lends credence to the idea that the Spheres were not directly responsible for the weakening of the Matoran.
Note, however, that this does not create any plot holes in Teridax’s Plan; keeping them in the Spheres for multiple years would have the same effect: isolating the Matoran from protodermis intake while subjecting them to a stressful situation.
So in summary, my theory is that the shrinking and memory loss of the Matoran on Mata Nui was not a direct result of the Matoran Spheres, and instead comes down to what is basically a vitamin deficiancy.
[BONUS: This could also shed some light on The Rebuilding. If memory serves me correct, the Matoran were rebuilt using protodermis from the Bohrok-Kal and Rahkshi, neither one of which have organic protodermis. They could provide materials for larger armour, but where did the stronger muscle come from?
The answer is that some of that protodermis was dissolved in the natural water from around the island and consumed by the Matoran.]