Blue-eye Dentition?

[coelacanth]

Loricariid dentition is a subject that has generated much discussion with enthusiasts, including some drunken conversation the night before the Convention last weekend!
Well, here's another bit of a twist.
There are four Blue-eyes here, three were obtained at the same time, from the same shipment maybe 7 years ago (I'd have to check exactly), the fourth was acquired much later. This one is clearly recognizable by being smaller.
I'm sure I remember all the originals having 'classic' Panaque dentition when they were obtained (unfortunately I have no photographic evidence of this), and so I had been surprised to see fairly recently when one of them was on the front glass that the teeth were actually now very different from what I remembered, being far more numerous and finer (due to their much reduced size the cusp pattern is difficult to see).
I eventually got pics of this, one of which I'm pretty sure is on the Cat-elog somewhere. At the time I assumed that all of the group now showed this dentition, as every time one was on the glass it looked the same.
Well, I've just been doing a bit of a feeding for the Public, and during this I noticed that two of the original fish were on the front glass having a bit of an 'argument' (both males).
I looked closer only to see that one fish was showing classic 'Panaque' dentition while the other had the more numerous and finer teeth.
So, we now have two fish, at least 9 years old, maybe more (they were several inches long when obtained), from the same shipment (actually out of the same box!), outwardly morphologically identical to my eyes, maintained in the same aquarium as each other continuously, fed the same foods, but with completely differing dentition.

Can someone please tell me what is going on, and what effect this could have on the use of teeth to differentiate species and even genera in the Loricariids?

[Silurus]

Tooth shape and number will change in fishes for any one of the following reasons:
1. Age
2. Sex
3. Environmental conditions (ecophenotypes)
Seems that your case is none of the above, so the possibilities are:
1. You have two different cryptic species
2. The two forms belong to the same species, but from different localities and what you are seeing is geographic variation. Of course, people will then have different opinions as to whether or not the two forms have enough differences to be considered different species.
3. The difference could just be due to chance mutation in one individual (chances of this happening are very slim, though).

[coelacanth]

1. You have two different cryptic species
2. The two forms belong to the same species, but from different localities and what you are seeing is geographic variation. Of course, people will then have different opinions as to whether or not the two forms have enough differences to be considered different species.
3. The difference could just be due to chance mutation in one individual (chances of this happening are very slim, though).

I really need to get each one out and photograph the dentition, but in 1000 gallons that ain't easy!
I am intrigued by the possibility of two sympatric cryptic species, as this would suggest sympatric speciation, the mechanisms of which are still open to debate.
If all specimens showed the same dentition I would be quite happy to believe it to be evidence that the teeth of these things can change quite naturally, either as the fish age to avoid resource competition with younger fish, or due to environmental stimulation, but this one that has retained the original dentition has thrown me.
I've been back out to try to count the teeth in each fish, but they are all now stubbornly munching bogwood and refuse to show me their mouths!