shaneandjennifer said..."How do they get vitamin A in the wild?"...from what I have read about insects some of them have quite a bit of vitamin A in them.
Sepiotuethis said..."If they can convert beta carotene then why do some people that provide it (in gutload or dusting) still get chams with signs of vit A deficiency?"....it might be from an imbalance (between D3 and A for instance). Also if the chameleon is unable to move out of the UVB the vitamin A may be destroyed. Maybe it could be due to hypothyroidism?
When I said..."do we know that the chameleon would not be getting too much D3 since it should already be making D3 from its exposure to UVB?"...I was thinking that if the chameleon had been under a UVB source enough to make the necessary amount and then was dosed with the codliver oil would it be too much at that time and the chameleon would then have to stay out of the UVB until the level "evened" out.
When I said..."Since A and D3 are antagonistic to one another if not in balance what does this mean??"..I was meaning...would the A simply counter balance the D3 or what? Would overdosing both D3 and vitamin A cause organ damage in spite of there being no signs of overdoses?
Here is some information about vitamin A/carotenoids in insects and any information that I have found concerning chameleons possibly being able to convert it...
Carotenoids in insects...
"Among insects, the silkworm, Bombyx mori, has had its carotenoid-binding proteins most extensively studied because carotenoids impart various colors to their cocoons".
"In invertebrates and vertebrates, carotenoids are ubiquitous colorants, antioxidants, and provitamin A compounds that must be absorbed from dietary sources and transported to target tissues where they are taken up and stabilized to perform their physiological functions."
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1831825
"The sample of caterpillars regularly eaten by these peoples was rich in beta carotene (provitamin A), and a 100 g ingestion guaranteed 323 percent of the recommended daily intake of vitamin A. "...
http://www.bioone.org/perlserv/?req....1646/0006-3606(2002)034[0273:NEOTIA]2.0.CO;2
"Possibly vitamin A or a derivative of vitamin A functions as the photoreceptor pigment for the photoperiodic reaction in this species of insect."
http://www.springerlink.com/content/q8737350x5057151/
"Silkworm pupae have ample amounts of vitamin A, locusts are rich in riboflavin and niacin, and honey bee larvae contain high amounts of vitamin D."
http://www.ndsu.nodak.edu/entomology/topics/goods.htm
"Meal worms are high in protein with essential vitamin A and B."
http://www.yourpetstop.net/Mealworms.php
"In spiders, vitamin E content ranged from 43.2–201.2 IU/kg; vitamin A levels ranged from 144.5–426.3 IU/kg."
http://apt.allenpress.com/perlserv/...&issn=0098-4590&volume=066&issue=02&page=0084
"Vogt has found the visual systems of a wide variety of animals depend on Vitamin A3. The largest group are the two-winged flies of the Order Diptera and the moths of the Order Lepidoptera".
http://4colorvision.com/files/vitaminAs.htm
Vitamin and mineral contents of commonly eaten insects in south western Nigeria...
http://72.14.205.104/search?q=cache...era+AND+"vitamin+A"&hl=en&ct=clnk&cd=15&gl=ca
P. brassicae contained vitamin A in the heads and it was found in the ova also...
http://books.google.ca/books?id=13T...&hl=en&sa=X&oi=book_result&resnum=5&ct=result
Vitamin A synthesis from beta carotene?
http://books.google.com/books?id=QL...ts=M-9HeL4uw7&sig=3lc_R5DhTVAS5-BoDAGyamPXum4
"Although the insects that form the diet of the chameleon are a poor source of preformed vitamin A, the presence of this vitamin in the yolk suggests its maternal synthesis from carotenoid precursers." This statement was concerning furcifer pardalis....and I've mentioned it in other posts.
http://www3.interscience.wiley.com/journal/95016303/abstract?CRETRY=1&SRETRY=0
"Measurable concentrations of retinol at all stages of egg development in the chameleons suggests effective conversion from carotenoid precursors, with concentrations similar to those measured in other lizard eggs."
Slightly off topic...interesting that cockroaches have been noted to be able to produce vitamin A but can live without it with no apparent problems.
http://www.jstor.org/pss/3795868