Definitely, very worth discussing and happy to do so, will respond more thoroughly a bit later
This is very interesting and fir me quite strange.
It must be somehow bias of the methodology and lights used I guess or maybe a small sample?
Though the babies of F lateralis live less exposed to sun than the adults, which is one of the few species getting extremely high doses of UV in the wild, as they run around unhidden all the day and are exposed to UVI exceeding 10, sometimes even 17 based on my measurements.
The total dosis that even the babies though not or limitedly basking is probably much higher that what your experiment was showing… were you a le to get an insight to the dosis and not only UVI exposure?
Or, inhibiting the fast griwth may be actually neneficial for the growth of the babies “to jave enough time” to build all nexessary steuctures oroperly and not speed up unnecessarily? Could this on contrary to the “disadvantage” of slow growth be a sort of protection against mutageneous and carcinogeneous impact of the UV light for the young chameleons?
It is very interesting to hear your comment in this.
Sorry for the delay, here are some thoughts about this
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I think the results are valid and not simply due to a low sample size (especially as the initial power analysis determined that n=6 per group is statistically sufficient to detect the difference I'd expect), but every experiment of course has limitations so I am careful to discuss this all in the context of captive keeping in the discussion of the article. Thought experiments about why the results are what they are are stimulating and interesting, but at the end of the day this was simply looking at what the results were on growth with easily reproducible (and commonly used) captive conditions. So regardless of the reasons for the results, I'd say the conclusions are the same-UVI 7 in captive conditions does not impart a growth benefit on F. lateralis in early development. As far as reasons though...
We did not venture into concluding what happens in the wild, simply what happens when people use commonly available setups with commonly available equipment. So the results here are not necessarily reflective of what happens in the wild and are more a warning that when raising neonates in captivity, folks should probably err on the side of lower UV vs. higher (within reason). Jon Hill at Ipardalis repeated my study in F. pardalis (although not peer-reviewed, I still value it highly) and didn't find a difference in panther growth rates in UVI 3 vs. 6, although a couple of big outliers in the UVI 6 group moved the results a bit (but not statistically significantly), and the groups were from different animal pairings so are not as directly comparable. So this is another piece of data supporting that in captivity, higher UVI does not seem to promote faster growth in a similar species.
https://ipardalis.com/blog/2021/08/04/baby-panther-chameleon-growth-rate/
One important consideration is that the relationship between UVI and heat with these lights is not the same as in the wild of course, as you know very well. So it's possible that the lateralis in the UVI 7 group met their UV needs more quickly, so hid more of the time and thus were not exposed to as high of temperatures had they been closer to the lights seeking UVB (where it is warmer due to inefficient bulbs but not directly proportional to the light intensity). Thus, they could presumably grow slower due to basically avoiding the higher UV areas. The study did not look into behavior of the lateralis babies, nor the amount of food consumed by the two groups. So, the "dose" of UV was indeed not measured. The answer could be in these parameters. Plus, compared to the wild, the UV was on constantly at the same UVI level all day. Perhaps this limits their ability to deal with UV vs. in the wild where they have more options and the UV exposure is much more variable depending on the time of day (or weather conditions, etc.). I'd be interested to see if the results were the same if the UV started off lower, then peaked midday, then dropped off again. This could also be an explanation-impaired regulation due to inherently unnatural lighting conditions. Personally, out of what I list here, I favor this explanation. I suspect that either the lateralis sort of "learn" that the UV is at peak levels constantly and adapt accordingly in conditions not reflective of the wild, or the fact the UV is at its max all the time in captivity (no natural and cyclical variation like in the wild) is inherently unnatural and thus, they don't perform as expected. Someday I'd like lighting systems that vary the UVI levels this way, to reflect natural lighting conditions better.
I am also in the position of responding to claims about lateralis behavior that I don't know the methodology or scope of. So, it is hard for me to respond directly to this and fit the UVI study within the context of your observations. I will try though, were these observations published? If so, I would love to take a look. If not, then I wonder if perhaps lateralis get high amounts of UV in the day some days, but then don't get high "doses" later on? Or perhaps the ones that get higher UV levels mate faster in the wild but die faster too, or perhaps lateralis behave differently in different regions, and the ones I used were derived from a distinct population not as tolerant of UV exposure. I'm not sure that there's precedent for that, but it seems feasible. These are just a couple of questions, I won't speculate much further on that since I don't have all the info. We know that for some other calumma species, they seem to seek out very low amounts of UVI (<1) as their average, even if they are exposed to transiently high levels. Obviously calumma generally have very different habits than most furcifer, but it's not unreasonable to suggest that even if baby lateralis are exposed to high UV levels in the wild, they might have some other way to compensate behaviorally that is missing in captivity.
https://pubmed.ncbi.nlm.nih.gov/30474137/
The idea about them "having enough time" is a very interesting one to me. I am not in the position to determine this one way or another though, as all the babies survived to at least adulthood (in other keepers' hands). It's possible that later down the line, we might see differences in longevity between groups though. Frankly I think this would be an excellent study, it would just take a lot of time and resources. I do a lot of work focused on how early life (in utero, until around weaning) exposures to things like bad diet or toxins can impact mammalian longevity and physiology, so I'm inclined to think there is likely some difference between groups with different UV levels at these critical early developmental windows. Someday I would like to get more conclusive answers though
