Mattias:
I hope this question gets a lot of interdisciplinary responses because I believe it touches on a number of interesting, if not sometimes paradoxical, conditions.
For example, it has long been held that there is an apparent inequity within the order Primates in their need for UVB light and resultant synthesis of vitamin D3. New World primates are generally far more sunlight-dependent than their Old World counterparts, and the frequency of observable metabolic deficits in UV-deprived New World primates would seem to validate this. Therefore, is there a greater ability for Old World monkeys to satisfy their metabolic calcium requirements solely through diet? If so, what is the nutritional source? What evolutionary processes bought about such a discrepancy between Old World and New World primates?
Secondly, the degree to which nocturnal animals may be absorbing UV light while at rest (during the day) should not be overlooked. While touring in Costa Rica I was very surprised to see sloths sleeping high in the trees fully exposed to sunlight. While very nocturnal in behavior, this taxa certainly seemed to have ample opportunity to absorb UV light. I’d postulate that other species do likewise.
Lastly, on occasions of having to hand-rear infant armadillos, it has been found that those infants being reared in the absence of UV light tend to fair very poorly and show evidence of metabolic bone disease (as one would expect from a calcium deficiency). Others raised on the same diet and exposed to sunlight on a regular basis have faired much better. The paradox lies in the apparent requirement for UV light exposure by infants of a nocturnal, subterranean taxa. Is vitamin D normally passed from mother to her nursing infant through the milk and, if so, how is the mother armadillo synthesizing vitamin D?
My apologies for raising more questions while providing no answers. The question opens a number of intriguing side topics.
Thank you for open up for a broader discussion. There is apparently lots of questions still to be answered. Not knowing much about different animals like you, but I guess there are several species living in the desert that will stay below the surface during the hot daytime and become active during the night. In more equatorial countries they might still get enough - you do not need a long exposure to fill your depot. Such animals might not exist in polar areas?
I agree. The number of polar species that would live underground and be primarily nocturnal are very few if any-- however this question is partially confused by the prolonged periods that occur on the poles when there is no light at all. During the polar winter everything would be either nocturnal (by definition) or dormant for relatively long amounts of time.
Of course this raises another interesting question-- How do polar species meet their vitamin D requirements during the polar winter and, do their metabolic processes change during the polar summer?
Mike Power presented interesting information at the last NAG meeting about how some of the suspected "elevated" D requirements of New World primates might instead be some of the first symptoms of early-stage gut atrophy. This of course begs the question about why gut atrophy is so common in many of these primates. As for polar animals, many fish have very high D levels, although I don't know the seasonality of this. Polar animals that eat fish may be able to receive sufficient D that way.
It is a good point - polar animals probably get their Vitamin D levels from eating fish. And fish get their Vitamin D levels from eating plankton that are able to produce Vitamin D - even if they live in polar areas?
For What it's worth ... dogs and cats absorb very little if any Vitamin from UV. It's all dietary in these species. Horses, cows, sheep and goats absorb from UV
Is that a general rule that carnivores absorbe less Vitamin D from the sun through the skin?
Perhaps ... not sure. Just know that dogs and cats pretty much get it from diet.
And what about mice? They are nocturnal or crepuscular. I'd be surprised if wild mice spent a lot of time in the sun during the day (like a sloth in a tree). I'm really interested in this question because mice are used in biomedical research on vitamin D metabolism. In the lab, people shave off the fur and expose the mouse skin to UV -and the mice synthesize D. But I wonder how mice do it in the wild. Or maybe lab mice are so different physiologically that that's irrelevant? I keep reading that mice supposedly lick it off their fur, but I've yet to see an actual citation and the similar belief that cows do that has been called into question.
Ever thought about the possibility that nocturnal animals eat food or other animals that are rich in vitamin D?
Article Effects of sunlight on behavior and 25-hydroxyvitamin D leve...
Thank you Jennie Dusheck and Mattias Andersson There are species in which (1) ultraviolet B (VUB) exposure is minimal or impossible, and (2) the skeleton system that is presumably so related to vitamin D related calcium metabolism than most things else, weighs much more than the rest of the body. They may provide different perspectives when we look at the relationship between vitamin D and skeletomuscular health in humans. (https://www.researchgate.net/post/How_do_nocturnal_rodents_get_vitamin_D)
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