UVB exposure Dendrobates

Part 2

This range is further subdivided into the sub-categories of UV-A (400–315 nm), UV-B (315–280 nm) and UV-C (280–100 nm). Only UV-A and UV-B solar radiation can naturally interact with biological systems, as wavelengths shorter than 290 nm are completely absorbed by the Earth's atmosphere (Antwis and Brown 2009).

Phosphorus is also an important component of bones and must also be included with calcium in the diet.Consequently, amphibians must have adequate calcium and phosphorus in their diet, and sufficient Vitamin D3 must be supplied through the diet or by UV-B lights. For a discussion of the provision of dietary calcium and phosphorus see (Amphibian diet and nutrition).

UV-B can be provided by several types of lights. Some of these produce large amounts of UV-B along with a large amount of heat. These are often used for reptile. However, fluorescent lamps that run fairly cool are preferred for amphibians because of their generally low UV-B and temperature requirements. For information on the best lights to use see http://www.uvguide.co.uk/Vitamin D3 can be provided orally in feed, through supplemented live feed (crickets)(Li et al. 2009),through dietary supplementation of live feed (Li et al. 2009; bioteck.org 2009), through mixtures used
directly for forced feeding, and as drops to the mouth (see Amphibian diet and nutrition). Vitamin D3 can also be provided topically through the skin. Vitamin D3 is fat soluble and in drops must be in a carrier like propylene glycol. Until further studies are completed for frogs we recommend a daily dose of 330 IU
Vitamin D3 per. kg per day given orally through drops. We consider it too difficult to give drops orally to very small frogs below 5 g, and even a measurable dose topically to frogs below 1.5 g.

Amphibians vary very highly in their exposure to UV-B. Amphibians include nocturnal, fossorial, or aquatic species with large variations in UV-B exposure. These vary from almost no exposure for fossorial amphibians or those that live in water more than 10 cm deep, to very high amounts for species that sun bask in during summer in temperate or tropical regions. The requirement for metabolic Vitamin D3 and the ability of UV-B to promote the production of Vitamin D3 in amphibians probably positively corresponds to their exposure to UV-B. Consequently, some species may have very low or no requirement for UV-B and low requirements for Vitamin D3 from their diet. Others may have very high requirements. Knowing the patters and the amounts in the requirement for Vitamin D3 and UV-B exposure between species from similar micro-habitats could help prevent hypervitaminosos.

However, even though we know that some species develop NMBD in captivity, even when fed crickets dusted with vitamin/mineral powder, there have been no formal studies to assess the needs of amphibians for UV-B and Vitamin D3. To avoid the need for the use of continuous UV-B lighting some zoos including Chester Zoo (North of England Zoological Society) and Rotterdam Zoo, Netherlands, have used boost application of UV-B on Dendrobatid frogs. This consists of high levels of UV-B for short
periods of 20 minutes monthly. Vitamin D3 can be stored in the liver and with mammals has a half life of about two weeks.

“The 'UV-B boost method was developed at Chester Zoo, UK, by Douglas Sherriff and Edwin Blake. Frogs are placed in an enclosure with a screen mesh lid that guarantees exposure of the frog to UV-B. A damp paper towel and cool room temperature reduce the chance of dehydration and overheating. If necessary lateral ventilation panels in the tank and a cooling fan can be used. This enclosure is placed beneath a UVB-emitting lamp – either an Osram Ultravitalux or a Zoologist Megaray – at a distance to directly achieve a UV-B level of 350-400 μw/cm2.
A finer mesh cover for very small frogs including (Ranitomeya reticulatus and R.lamasi) results in a reduction of UV-B exposure to about 30μw/cm2. Frogs are ‘boosted’ monthly for 20 min. Observation of the frogs throughout the boost and use of a timer is important to avoid problems with over-exposure. For example, a group of R.reticulatus was inadvertently boosted for 45 min. This resulted in superficial discolouration of the skin that healed within a fortnight. These frogs then went on to reproduce successfully (Gibson pers. com.).”

Studies of UV-B/Vitamin D3 and amphibian health offer an ideal research focus for zoos, as very little is known about this subject that is so important to conservation breeding programs and the welfare of amphibians in captivity. Zoos, privates and other institutions can through pioneering studies of UV-B and Vitamin D3 improve the health of captive amphibians, and provide basic knowledge to support the ecology and physiology of amphibians in nature. Studies of UV-B/Vitamin D3 will also encourage studies of other nutrients and micro-nutrients. Studies design for studies of larval and adult amphibians. We use plastic boxes (41 cm L x 34 cm W x 17 cm H) with a hole cut in the lid and covered with 1 x 1 cm x 1.7 mm plastic garden mesh. The bottom of the box is covered with paper towel and an 18 cm diameterx 2 cm depth water bowl provided. Paper towel was changed every two days and water replaced daily or with soiling. Lighting is provided by fluorescent lamps suspended over the mesh. For UV-B treatments strip lights are Zoo Med Reptisun 5.0 UVB (14W, 375mm/15”) or Zoo Med Reptisun 10.0 UVB (15W,475mm/18”). An aluminum hood increases UV-B levels by 40%. UV-B levels were measured with a Zoo Med ST-6 Digital Ultraviolet Radiometer (range 280-325 nm, peak 290 nm, accuracy ± 10%). UV-B levels for Reptisun 5.0 in the box vary from 9-24 and with the Reptisun 10.0 from 23-50 μw cm-2.Few studies have examined the behavioural sensitivity of adult amphibians to U-B radiation; however, Han et al. (2007) found UV-B avoidance behaviour in two Neotropical poison-dart frogs. Using a simple enclosure that provides UV-B or equivalent light without UV-B, and a web cam with a time lapse imaging system, researchers can with minimal effort reliably test UV-B avoidance behaviour in wide range of frog species. If the study is investigating behaviour the box can be partitioned with a vertical barrier, with a UV-B fluorescent tube either side, with Mylar blocking the UV-B on one side (Han et al. 2007). Responses in UV-B/Vitamin D3 studies include x-rays, weight and length, skin colouration and condition,and Vitamin D3 levels. The inability to assay Vitamin D3 levels except for plasma or whole body are restrictive. Blood can only be taken from larger amphibians In ectotherms, about 50% of the blood can be removed at one time. This is roughly 5% of the body mass. The smallest amphibian from which 0.2 ml whole blood needed for many assays can be sampled is 4 grams, and from which 0.5 ml whole blood can be removed weighs 10 grams (NWHC 2009). Tests for Vitamin D3 (calcitriol) using radio imumo-assay require on drop of blood.

Above: A highly adapatable and robust habitat for testing UV‐B is a plastic box with a hole cut in the lid and plastic garden mesh covering. A fluorescent light can be placed over the top of the mesh and then covered with analuminium foil cover. The aluminium cover reduces dispersion of the light and increase UV‐V in the box by 40%.​

Left: Groups of many replicates can also be housed in similar arrangements. Juveniles of species that are sun baskers including Amazonian milk frogs (Trachycephalus resinifictrix)are easy to keep on a foam mat in a water bath in plastic containers with curtain mesh on top. This technique enables the housing of many replicates in a small area.

Amphibians physiologies and their needs for UV-B and Vitamin D3 possibly vary dependent on their natural UV-B exposure. At Antwerp Zoo for research we are categorising anurans as receiving high, medium and low UV-B exposure in natuire. Green and Golden bell frogs (Litoria aurea), and some African reed frogs (Hyperolius spp.), that sunbask in the hot summer are considered high UV-B species. Amazonian milk frogs(Trachycephalus resinifictrix) males call from tree hollows but move during the day toward the canopy. The metamorph frogs have been observed to prefer exposure on foliage in captivity. They are related to the poison dart frogs and also produce a milky secretion that is probably discouraging to predators. Consequently, we regard T. resinifictrix as a medium UV-B requirement species in respect to natural UV-B exposure. Low UV-B exposure species are those that are crepuscular including tomato frogs (Dyscophus antongilii). How these categories relate to UV-B and Vitamin D3 needs, and to behavour in respect to UV-B levels, are the subject of ongoing studies. Right: Portable x-ray machines enable x-rays of very high resolution. This x-ray shows the early skeletal development of a tail bud T. resinifictrix only about 14 mm in snout-urostyle length

I think the main summary is that your frogs need vitamin D3, so that they can metabolize calcium properly. Many anurans (people too!) use UV-B radiation from the sun to synthesize vitamin D3, but in captivity many anurans don't receive the UV-B that they normally would, so supplementation of vitamin D3 to their diet is essential to their development. The article goes on to say that zoos have tested adding UV-B to frogs and found out that many frogs can behaviorally regulate their UV-B intake (some can detect UV-B with their eyes). The article also stated that "Han et al. (2007) found UV-B avoidance behaviour in two Neotropical poison-dart frogs."

Reading this article makes me think about how member Mworks stated that he supplements his histrionicus with UV-B lighting (monthly I think), and that they come out from hiding and "sunbathe" when he does so.

The formation of D3 is controlled by feedback mechanism.. if there is sufficient D3 in the animal, further conversion of D3 will not occur so there isn't a risk of overdose by supplying access to UVB as well as supplementing the frogs. Overdosing of D3 is pretty much restricted to the oral ingestion of vitamin D3.

There is data slowly emerging from other taxa (including those typically considered to not need additional D3 (snakes), that if given the opportunity they will behaviorally maintain a higher circulating level of D3.

For some discussion on these topics see http://www.solarmeter.com/pdfs/paper2.pdf

AVMA - American Journal of Veterinary Research - 69(2):294 - Abstract (not a free copy)

There is some evidence that allowing the frogs to behaviorally modify exposure to be of benefit to the frogs. This means that more thought has to occur in planning as the frogs are known to avoid (if possible) excess exposure including choosing calling perches that are not exposed to UVB. See http://people.oregonstate.edu/~blaustea/pdfs/HanBiotropica2007.pdf

Ed

Once again Ed thankyou for posting. You have just prempted a post by us about this very subject.Do you have any information on anystudies or on how the use of uvb lighting might be of benefit to tadpols and helping with sucessful morphout,ie prevention of sls.?
We are just experimenting with one of the new arcadia T5 24watt D3 6% over our tad rearing set up. Arcadia seem to have done alot of reserch into this product,from my limited knowledge it seems to be the best option available for our dartfrogs,but i personnally would like a lower wattage option, in some tanks we only use 14watt. As above we also utilise T5 bio vital bulbs over our vivs.
We have taken the pragmatic view of using different types of glass (ie low iron) to give differing levels so the frogs can self regulate,in viv. With the tadpols we are giving a good piece of oakleaf for potential shade,again for self regulation.Deep thought is given, as best we beginners can, to our frogs in viv being able to use the uvb and behave normally in areas of the tank that are shaded from it aswell.
Our leanings towards this were 2 fold,1 mworks posts and 2 obseving our auratus "sunbathing" in a shaft of sunlight early mornings standing high legged,i would hasten to add we moitored temperatures very carefully during this very brief early morning period,with concearn about viv temperatures rising excessively,but all is well. When our room is eventually finished we will be running a 2 fold lighting system uvb bulbs in the center of the day and an led system on throughout the day...any thoughts?
Paramount in all this is the thought of self regulation by our charges
regards
Stu

based on the huge amount of data out there I would not use UVB for tadpoles.. there is some good data out there that tadpoles may not avoid damaging levels of UVB

See for example Larval amphibians seek warm temperatures and do not avoid harmful UVB radiation

It also makes the tadpoles less tolerant of poor water conditions (see for example http://people.oregonstate.edu/~blaustea/pdfs/Macias_et_al_STOTEN_07.pdf

for a more generalized discussion see
http://www.uoguelph.ca/~salex/Can. J. Zool. 77.1956.1966 (1999).pdf


Ed

Like Ed I believe that providing UVb for tads may not only be unnecessary but may be potentially damaging to tadpole development. When providing the histrionica with a UVb session I noticed a visible tad in one of the brom axils would 'go deep' when the bulb was switched on. Finding another tad in the BriBri viv I tried with the UVb directed on it's axil - similarly the tad 'went deep'.
This happened several times so my conclusions were that the tad knew what it needed and UVb wasn't on it's list.

Since that incident I have never thought of providing UVb for my tads. I also notice that many now provide constant UVb for their frogs. As I have mentioned previously I decided not to do this as after about 30 mins 'sunbathing' under a 10% Arcadia bulb every frog I have leaves the 'UVb lit' area and re emerge when the bulb is switched off.

I have also started to open the doors on some of the vivs with frogs I trust won't jump out. Of course I sit with the lamp ensuring no escapes and I have noticed that the frogs seem to have an awareness of UVb strength as they 'bathe' about 3 inches farther back than when the doors are closed and the UVb is going through the Optiwhite glass I use on all my viv doors. Coincidence - I don't know yet - I should have a better idea after a few more months experimenting.

Regards
Graham

Mworks said:

Like Ed I believe that providing UVb for tads may not only be unnecessary but may be potentially damaging to tadpole development. When providing the histrionica with a UVb session I noticed a visible tad in one of the brom axils would 'go deep' when the bulb was switched on. Finding another tad in the BriBri viv I tried with the UVb directed on it's axil - similarly the tad 'went deep'.
This happened several times so my conclusions were that the tad knew what it needed and UVb wasn't on it's list.

Since that incident I have never thought of providing UVb for my tads. I also notice that many now provide constant UVb for their frogs. As I have mentioned previously I decided not to do this as after about 30 mins 'sunbathing' under a 10% Arcadia bulb every frog I have leaves the 'UVb lit' area and re emerge when the bulb is switched off.

I have also started to open the doors on some of the vivs with frogs I trust won't jump out. Of course I sit with the lamp ensuring no escapes and I have noticed that the frogs seem to have an awareness of UVb strength as they 'bathe' about 3 inches farther back than when the doors are closed and the UVb is going through the Optiwhite glass I use on all my viv doors. Coincidence - I don't know yet - I should have a better idea after a few more months experimenting.

Regards
Graham

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Again Graham thankyou for your thoughts,as with Ed your wisdom is greatly valued,i thought that the low levels available to our frogs as overhead,might be a way of self regulation,its is only the back 15cm or so of our vivs top,that actually uses low iron/optiwhite glass,in all vivs i think this area of background is heavily planted,and lower levels in full shade so a frog would have to actively seek said light,the majority of the viv top is constructed ofnormal 4mm which i thought only let very low levels of uvb through, which i didn't think would be of any potential risk to our frogs,coupled with the uvb lighting only being on for the middle part of the day i believed,i had a system figured that would let them chose and not be reliant on me,chosing for them.
As regards the tadpols interesting observations,i might have to change things,i need to read through Ed's links,which you both know how i struggle with thses scientific data type posts so will need to be of a clearer head to assimalate something from them,that is if I can understand them at all,as before i don't think i see letters quite the same as other folks do. I based my initial thoughts for using this with them, on factors such as low strength bulbs,poor penitration of rays into water.But of course my simple laymans/stockmans logic,not that of the more scientic data that you guys are able to access ,but for me is next to impossible to read,i deeply struggle with the english,always have always will.I have also read that uvb could be beneficial in combatting fungal infections and help with water quality.
With our 14 watt bulb we have so far encountered no visable problems,but it is very early for us,in less than a week i guess 3 more tads will morph all look ok i think,but its just so early for me/us yet,first season and all, its utterly impossible to be sure of anything we are doing .
Thanks again buddy and to Ed
regards
Stu

Actually if you dig around in the literature, there are a number of papers that indicate increased susceptiability to fungal infections for tadpoles exposed to UVB light. We should keep in mind that most of the dendrobatid tadpoles are not going to be found in locations that are going to have significant UVB exposure. (leaf axils (shaded by other leaves/tissues, small pools or puddles under the canopy are two off the top of my head) so they are probably going to be very sensitive to UVB.

The whole idea for UVB usage for tadpoles was due to a practice in a European Zoo that was published in the old British Dendrobatid Group News letter. It used to be available on the old BDG website, but since that went down, I haven't seen it around. It was done during the old days when there was a lot of voodoo guesswork on how to prevent spindly leg syndrome in tadpoles. It hasn't been supported by the literature as a good practice and we have a much better handle on spindly leg now due to some recent studies.


Ed

Ed said:

Actually if you dig around in the literature, there are a number of papers that indicate increased susceptiability to fungal infections for tadpoles exposed to UVB light. We should keep in mind that most of the dendrobatid tadpoles are not going to be found in locations that are going to have significant UVB exposure. (leaf axils (shaded by other leaves/tissues, small pools or puddles under the canopy are two off the top of my head) so they are probably going to be very sensitive to UVB.

The whole idea for UVB usage for tadpoles was due to a practice in a European Zoo that was published in the old British Dendrobatid Group News letter. It used to be available on the old BDG website, but since that went down, I haven't seen it around. It was done during the old days when there was a lot of voodoo guesswork on how to prevent spindly leg syndrome in tadpoles. It hasn't been supported by the literature as a good practice and we have a much better handle on spindly leg now due to some recent studies.


Ed

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Absolutly see your logic here Ed,of course i need to walk where our dartfrogs live observe,think evaluate and then put that into practice,that would be the way for my brain to work out how much light/not only uvb our frogs need,but i doubt this will happen so every conversation like this becomes hugely important. I wasn't actually aware of the thoughts by the BDS. But our use of uvb has been very much driven by the wish to not see sls,your last sentance becomes all important now because i deeply feel there is something on sls that i have totally missed out on,i'm also warey of asking more here on your thread because it wll take you thread totally leftfield i fear and into a disscussion on sls.
Ed i have had ago at the first two papers,laymans thoughts
1 my conclusion is that the tadpols will congragte in areas of water that is the right temperature for them,if that means too much uv this is not as important to them as the temperature...even if it harms them
2nd paper when testing for problems with pollution ie nitrate uvb can have an exagerating effect to the consequences of said polution,so needs to be factored into experiments.uvb can act as a "catylist" making environmental problems for phibs greater
have i got the gist of these studies?
Finally with regard to your last post,are there any studies any tables of which darts receive higher light levels which darts live in the darkest places...is there any correlation between different morphs of a species and light level?
This would give us a fairly simple laymans guide to how bright our viv should be,and how much uvb a given dart might need, well maybe.
i'm gonna have a go at that third paper now,wish me luck
thankyou
Stu
Ps i'm probably drawing the wrong conclusion here but do auratus live in real dark places...dense cover overhead,maybe moreso than tinctorius?