Indoors without UV is a quick way to MBD in panther chameleons. Im not just saying that, is been proven.
I have seen a couple of nutritional studies in progress before and would just say that just because a study "proves" something- doesn't always make it so. What it proves is that under the conditions of the experiement, it is so.
I have been lucky to see a couple of nutritional studies involving lizards underway and talk with different dvm phds (coincidentally those running both studies were similar qualifications) running the studies and was surprised to see that the setup for the lizards involved was what I would definitely consider suboptimal.
Heat delivery method, heat intensity, ambient temperature, lighting intensity, lighting spectrum, nutrition, supplementation, water quality and delivery, stress levels of the lizard, etc, etc all work together for the end result in the lizard. Studies usually only focus on 1 of these variables and others are ignored.
Heat is far more important than I think it is currently given credit for in these studies, and in both studies I got a peek at heat was provided in weird ways (one study was using "sizzle stones" for the primary heat source. Another used ambient room heat turned up and very very weak basking spots). If you cannot get the heating correct, the rest is going to be skewed.
I'm not recommending anyone toss their expensive lighting away, but I *have* run casual long term trials of my own over the years with a couple of lizard species that were supposedly proven to be unable to use dietary vit. d3 and know for a fact that the studies proving that were wrong for those 2 species (Iguanas and bearded dragons)
I know this because mine grew from babies to adults with great bone density (shown via x-ray when living and necropsy after death) producing excellent looking viable eggs hatching more babies without ever being exposed to UVB lighting or any kind. You can't argue with success.
These were not chameleons- but I really seriously doubt chameleons are *that* different from other diurnal basking lizards.
The guy who introduced me to breeding chameleons years and years ago often did not use UVB lighting himself and he had success with several species, and in the early days, maybe I didn't either sometimes because I was using ge chroma 50s, sometimes combined with ge blacklight tubes. I had been told at the time by our local lighting store that chroma 50s were the equivalent of vita-lites, and their output was no different. It was many years before I learned this was incorrect. Remember this was a few years before reptile specific tubes were on the market. State of the art for lizards at this time was vita-lite. Blacklight tubes were being tried for chameleons and desert lizards.
Somewhere (his book or maybe an online interview I read) Ferguson mentioned something about someone he was confident was successfully breeding panthers without UVB also, but ferguson himself was unable to provide enough d3 via diet without making the dose needed for absorption dangerously high.
IMHO this might be because he provided most of his heat by heating the room the chams were in rather than providing strong warm basking sites locally. I'm pretty sure I remember reading that was how he provided heat. To learn more, please support this site by buying his book from the bookstore- it's an excellent read.
I have been uncomfortable with the low basking temps I see recommended for species like panthers and veileds nowadays, and the reason is that if the lizard cannot cook from time to time *when it wants* it cannot operate at maximum performance. I'm talking about ability to absorb nutrition properly, and I'm talking about immune system function. This is my opinion based on experience and rational logic.
In the case of the cited skin study in this thread- come on scientists!- shed skin does not necessarily give us an accurate idea of what living tissue is capable of at all. Furthermore, in humans- people near the equator have dark skin because it is needed to protect them from the UV from the sun. People far away from the equator have pale skin because the body is doing all it can to get what little UVB it can from the sunlight most of the year excepting the summer so it can make d3. Possibly a chameleon that has turned dark to warm itself in the sun absorbs more uvb than a chameleon with pale skin for example.
I think we can rely on experience to say that we know chams can produce d3 from light. I never use d3 during the summer when my lizards are outdoors, yet they grow and look great. Ferguson provided his d3 through full spectrum lighting and his animals did fine over generations.
One last thought- in humans our need for vit d3 is only now beginning to be understood in the last several years. One thing that has been surprising that has been learned is that optimal levels for us are much higher than previously thought. Another thing that is surprising is that how much we need varies incredibly by hundreds of percents from individual to individual, even those among those who are very similar genetically. The only way to determine our proper dose is to run blood work from time to time while taking it.
However- it is also known that if we have proper lighting we can safely get al the d3 we need from the light. Sunlight or "safe" tanning lights. (I have no idea what those are- I just read this info recently). Scientists say no human has ever overdosed from d3 acquired from sunlight. I think that's relevant to our discussion here with chameleons. *If* our lamps deliver uvb the same way sunlight does (and that's a mighty big and potentially dangerous "if"), it should be impossible to overdose them via a good brand.
There is still a lot to learn about this stuff.
Personally, I've come to see full spectrum lighting as a safety thing. It isn't a matter of whether it can it be done without it, it's a matter of how it makes things easier with it, there are other benefits it provides besides the d3 (physiological and psychological and perceptual), and it can help make up for slight nutritional and temperature mistakes.
I'm not opinionated or anything.
