UV lights in the care of caudates

I'm hoping that we can start a discussion on this - not for amphibians in general but for caudates in specific. The class, amphibia, is too large and encompasses diurnal/basking species which would seemingly have different requirements and tolerances for UV light. If we could limit the discussion to caudates….but then on the other hand, there may not be much of merit to discuss, as there are little hard data available.

There are several considerations that come to my mind when discussing UV light needs. A few of these:

•What is the natural UV light environment inhabited by the species
•Sensitivity of the skin to UV light and resistance to UV damage. I believe that in lizards there are varying degrees of sensitivity e.g., nocturnal leopard geckos vs. bearded dragons, green iguanas, etc. that suggest different UV needs. Snakes I believe also vary in their need for UV light. Does the same exist for caudates and does the caudate skin secrete photo protectants (assumable to some degree?)… and does this vary by species.
•Do caudates which are mostly nocturnal, need UVB to synthesize/activate vitD or can this vitamin be adequately supplemented in the diet.
•If needed, how much UV is needed? At what levels and for what time period. It would seem that even nocturnal animals are exposed to some low levels of diffuse or reflected UV light when in hiding during the day.
•If one decides to use UV lights…what one(s) should be used? There are many different types on the market which vary in strength/dose/output of UV provided. One UV light is just that – one UV light. There are fluorescent bulbs that vary in UVA and UVB outputs (2-10%), compact fluorescents, incandescent “full spectrum”, halogen, sun lamps, mercury vapor, black lights, etc. Very confusing for the average caudate hobbyist. How might we define ‘low level’. When someone is using a UV light and their animal starts having skin or eye problems, I typically feel that the UV light should be removed.
•How to use in a vivarium…. using a mole salamander as an example. If one has a 10 gallon tank even with hides, it may be difficult for the animal to escape the UV from a fluorescent tube light (many moles tend to show their faces even under hides). It would be a different story for a 40 gallon viv with a small UV light at one end or perhaps in a densely planted aquarium with lots of hides.

From a pathological standpoint, corneal opacities and skin discoloration in amphibians have been suspected as a result from UV lights. Amphibians can get sunburned (erythema, blistering, sloughing) if exposed to direct sun light and I might assume this could be extrapolated to UV light if intense. Experimental high doses of UVB radiation have produced skin erosions and ulceration in one species of newt. In work done with anuran eggs and tadpoles, high levels of UVB produced ocular lesions, skin thickening and hyperpigmentation. I’m a bit concerned (perhaps unreasonably so) with an inexperienced caudate keeper who uses a reptile UV light set-up….and I caution against this.

Again, as the question of necessity of UV lights for caudates is often asked – it would seem a topic worthy of discussion. I would welcome other’s thoughts on this and any data anyone may have to share or experiences positive or negative. If we understand low-level UV light to be beneficial – what are we defining as low-level and for what photoperiod per day?

As there seems to be a paucity of hard data, if you have any experience with using UV light either positive or negative it would be beneficial to share your experiences. Perhaps we can generate some anecdotal information - caudata.org would seem to be the perfect place to explore this. If you have experience, would you mind sharing:

1. What your set up is - type of viv, type of UV light/UV output, distance of light from viv floor, light covering whole viv or just one section, etc
2. What photoperiod do you use per day of UV light
3. For what species do you use UV light and are they typical or atypical in coloration (e.g., albino axolotl vs. wild type color)
4. For what length of time have you used (are using) UV light
5. Why you decided to use UV light
6. Description of positive or negative outcomes associated with UV light use
7. Any other information you think would contribute to the discusssion


Thanks much
Jan

I provide fluorescent lighting over almost all of my caudate enclosures. I keep Tylototriton, Echinotriton, and a trio of P. chinensis. It has always been my understanding that the species that I keep need little to no UV lighting however I admittedly have not researched the topic in any great detail. I use the lights both to provide a day/night cycle (they are on around 14 hours a day on average) and to keep the plants healthy. I use several varieties of hardy, low light requiring species of aquatic and terrestrial plants, depending on the enclosure design. I use glass aquariums and depending on the individual enclosure the light source is anywhere from approximately 12 to 18 inches from the substrate or water surface. I have two 40 gallon breeders, 2 65 gallon, a 20 high, and several 10 gallon and plastic "critter keepers" - which do not have lights - for the juveniles. I am getting ready to upgrade those animals in the 20 high and some of the smaller tanks to a 40 breeder and 50 breeder. I do not use any special type of fluorescents, usually just the daylight tubes available at Lowes. Lots of cover is provided in each enclosure and most of my animals tend to hide during the day except at feeding time, when many of the beggars will come out. The exception to the previous statement would be the E. andersoni (I rarely ever see them even move). The coloration of all of the animals seems to be consistent with those that I see pictures of from the wild. For all of the three foot enclosures I use 22 inch (? I think - I'm at work right now) bulbs. The smaller enclosures obviously have smaller bulbs.
Chip

Someone I know used a UV lamp with one experimental group of T. verrucosus sub adults (another group was not exposed to it), and it rapidly led to darkening of the skin, lethargy, high stress levels and death in a few animals after only a relatively short time. I don't know the strength of the bulbs used, or the length of exposure time, unfortunately. Very annecdotal, I know, but the UV did seem to have very detrimental effects.

Thanks for sharing Foster. Just as a point of clarification, the daylight tubes you use would not provide UV? From my limited understanding of lighting, daylight or full spectrum, does not provide much to any UVA or UVB - the spectrum of light emitted extends to just near ultraviolet...admittedly, that might vary with manufacturer. Would you agree with this or do you have a different understanding?

I believe the same applies for cool or warm fluorescent lights re UVA/UVB emission.

I agree that these are not UVA or UVB emmiting bulbs. I could very well be mistaken but I do not believe that the requirement (or lack thereof) would justify the cost. Even back when I kept many of the sun loving lizards that I used to breed I rarely used anything other than a standard bulb from Lowes. I kept them outside during the summer months and supplemented with D3 during the winter. I apologize for not reading your post more thoroughly before responding, I suppose that I really have nothing to offer on the matter now that I have re-read your original post (that's what I get for posting before having my coffee).
Chip

It’s a very interesting discussion topic and I hope someone has the answers. I can’t find any references to studies on UV exposure and vitamin D synthesis in amphibians – let alone caudata specifically. The general feeling seems to be that it shouldn’t be ruled out. And with my cynical hat on I doubt those manufacturers of full spectrum or UV bulbs want to miss out on a sales opportunity.

The fact that high levels of UVB have been shown to be damaging to amphibians suggests that we should not expose caudates to anymore UVB than they would experience in their natural environment. Nocturnal caudata would typically have very low exposure to UVB – perhaps some low level reflection in hides/leaf litter or when aquatic animals surface for air (UVB only penetrates a few cm into water). When the demise of the ozone layer was blamed on amphibian declines a number of experiments were done on eggs/larvae (the stage when amphibians receive the most exposure to UVB). They actually found that eggs and larvae were more tolerant to UVB than ambient levels could provide. I don’t know if UVB tolerance has been tested on adult caudata but I’d guess that their life style lends itself to a higher sensitivity than say a canopy dwelling tree frog.

Personally I think keepers should be cautious about exposing caudates to higher than normal UVB levels. There’s enough anecdotal evidence of long lived captive caudata (20 years +) to make me believe special lighting is not required. If lighting is desired for display purposes or you want to provide natural lighting, a combination of broad spectrum fluorescent and long wave UVA tubes should be fine.

Hi,

I would certainly agree that we don't have much in the way of real answers here. I'm not aware of any studies off-hand dealing with uv levels where caudates naturally dwell over 24 hour periods, although some such observations at least have been made in reptiles. Maybe some herpetologists with uv meters could do some field work with wild salamander populations.

My own view is that low levels of uv should always be provided, unless there is no way the animal would naturally be exposed to it (e.g. completely subterranean cave dwellers). If we don't know whether it's required, but it may be, we should err on the side of providing it. There is increasing evidence that full spectrum lighting is in fact beneficial to many species (notably birds and snakes) that are not traditionally provided with it.

Having said that, obviously it must not be too intense or too pervasive - which can unfortunately be difficult in small enclosures (one more reason I feel most amphibians are kept in enclosures too small to provide a reasonable range of microclimates, but that's another debate). For caudates they must be able to hide away from it as thoroughly as they wish. I tend to recommend a lower output full spectrum tube or bulb (certainly not the higher uv output ones now available for reptiles), as high as possible in the enclosure, and with adequate hiding places.

Any animal housing has to provide a suitable range of microclimates - areas of specific temperature, humidity, illumination, air/water flow etc - within the animals normal ranges, so that it can choose which one it prefers (which can vary with season, time of day and other factors). In general we don't consider this enough in my opinion. Anyway, it seems logical that some sunlight, in whatever attenuated/reflected/shadowed form may reach most if not all caudates at some point in their diurnal cycle, so I think the option should be there.

Just a comment that I also tend to feel the uv A is as important or in some cases maybe more important than uv B, although that gets all the attention - uv A wavelengths are very important in diurnal rhythyms and activity levels in many species studied.

Anyone interested in this subject should read www.uvguide.co.uk - although based on reptile lighting, for a discussion of the basics and more of uv it is hard to beat.

Hope this helps,

Bruce.

Bruce, thanks much. I read with interest the link you provided for the UK guide to reptiles and UV light - great resource.

As a general point of clarification to this discussion is … what we mean by UV light. Would we agree that these are some types of lights:

1. Specialty UV lights that are designed to emit UVA and UVB (at variable emissions)... but that is their design none the less
2. Daylight or full spectrum lights that are used to simulate daylight and emit small amounts of UVA but most do not emit UVB
3. Cool and warm fluorescent lights which do not emit UVA or UVB
4. Black lights which emit UVA

This causes confusion I think. When I think about the need or lack thereof for UV light in caudate care, I am considering the need for specialty lights designed to have UVA/UVB output, i.e., lights for reptiles….which I have never used on my tigers out of fear of skin and ocular concerns. The link you provided showed a study of shed skin from various lizards and the percentage transmission of UVB. The shed of 'sun worshiping' lizards had a small percentage of transmission (thick skin, resistant to UV damage) as compared to crepuscular or nocturnal lizards – large percentages of transmission. This is a leap and an extrapolation, but one could surmise that a nocturnal caudate would have even less resistance to UVB than a nocturnal lizard.

From your response, your “view is that low levels of uv should always be provided, unless there is no way the animal would naturally be exposed to it (e.g. completely subterranean cave dwellers)” and “recommend a lower output full spectrum tube or bulb (certainly not the higher uv output ones now available for reptiles), as high as possible in the enclosure, and with adequate hiding places.” This would be providing very low levels of UV if we agree on the above definition of daylight or full spectrum lights. Many caudate keepers I think use these type of lights especially where they also grow plants in their vivs – but yet would not consider using “UV lights”…as Mark and Foster have discussed in their posts above.

Are we on the same track Bruce – or am I overlooking something you have said? I’m just asking for the sake of clarity and that we may all have different assumptions about what is “UV”.

jan said:

Bruce, thanks much. I read with interest the link you provided for the UK guide to reptiles and UV light - great resource.

As a general point of clarification to this discussion is … what we mean by UV light. Would we agree that these are some types of lights:

1. Specialty UV lights that are designed to emit UVA and UVB (at variable emissions)... but that is their design none the less
2. Daylight or full spectrum lights that are used to simulate daylight and emit small amounts of UVA but most do not emit UVB
3. Cool and warm fluorescent lights which do not emit UVA or UVB
4. Black lights which emit UVA

Click to expand...

Hi Jan,

Yes, sorry, my mistake, I think we are talking slightly differently here. When I say full spectrum, I'm referring to the specialist lights for reptile housing, which emit light in the UV-A and uv-B wavelengths, your category A. Arguably still not 100% full spectrum, but a lot more accurate description than the category 2 ones. Sorry I didn't make that clear.

Your category 2 are indeed often described as full spectrum, although I think maybe less commonly over here in the UK (thankfully, since it's misleading). Certainly some uv studies suggest that almost all bulbs produce at least trace amounts of uv-A and even uv-B, but they are insignificant in a practical sense.

Blacklights, though variable in terms of usage of the term, tend to be very intense uv sources, and I would never use them with amphibians (or reptiles) - often been associated with problems in the past.

When I say low level of uv-B, I am thinking of the lower output FS (full spectrum) reptile bulbs ("2%" FS bulbs). As I mentioned, I would also ensure it isn't too pervasive - the animals can hide away from it thoroughly, which might even necessitate a deflector screen below the bulb so little or none reaches the vivarium substrate directly. But I appreciate that may be difficult in smaller enclosures. I would argue, however, that if your enclosure is too small to provide an adequate range of microclimates, it's too small period : ).

In theory, if we assume some diffuse/attenuated sunlight reaches most caudates at some point during the daily cycle, we can either start with light approximating sunlight and make equivalent light levels available in the captive environment or we can measure the exact spectrum and light levels in the wild and use them in captivity. The latter option is obviously ideal, but currently completely data-deficient as far as I'm aware. I think the former option is therefore the next best option.

If FS light access is an option (as always, it should only be an option) for the animals, it extends the range of available microclimates which, if it is possibly within their natural range of microclimates, is surely a good thing?

It would be interesting to get some studies on both wild caudates as I mentioned before, and captive ones with various hiding places and observations on their usage or avoidance of variable uv-levels - but very difficult (hand-held uv meters generally too small to fit in caudate hiding places!).

Hope that clarifies things.

Bruce.

Thanks much Bruce for the clarification. I find the descriptors confusing and to your point - definitions and perhaps even products (or the marketing thereof) may well vary between countries. I wonder if this may be in part responsible for the variety of recommendations seen regarding 'UV light' use in general in the care of captive animals......more musings:happy:.

From what I've read and seen I do not believe any salamander requires UV light. Whether or not it is detrimental is another matter but common scientific sense tells me that subjecting an albino axolotl to UV light can't be a great idea.

Regarding frogs, I'm relatively certain that some frogs need UV light (or a reduced dose of it, like Phyllomedusa, otherwise why would they bask?) and that some are impervious to it (such as African Bullfrogs). Of course I haven't done any scientific studies so this is just my opinion.

My only personal experience on the issue: When I needed to replace a couple of the overhead fluorescent tubes that are above my tanks, I decided to buy two reptile "2%" UV bulbs. These are the lowest-strength, and they sit ~3 feet above the tanks, so the amount of UV is very small. There are 4 bulbs up there, and only two are the UV type, the others are GE "plant & aquarium" bulbs. These lights have been up for over a year (it's time to replace them, if I care about UV output). Conclusion: I haven't seen any particular effects, good or bad.

On a practical note... if your tank has a glass or plastic lid of any kind, don't bother trying to add UV light. It won't penetrate any type of glass or plastic to any significant degree.

Considering Pleurodeles waltl has been found in caves and is by no means a subterranean caudate I think it is safe to say no caudate requires UV light.

In captivity though, UV lighting can be replaced with good supplementation and feeding even in animals that seem to require it(diurnal lizards, for example).

I've thought it interesting how most caudate keepers seem to be more lax with supplements than other amphibian/reptile keepers. Many state that terrestrial frogs etc. cannot survive without Calcium with Vit D3 supplementation. I think most people on these boards do not use supplements even with terrestrial caudates(myself included).

fishkeeper said:

I've thought it interesting how most caudate keepers seem to be more lax with supplements than other amphibian/reptile keepers. Many state that terrestrial frogs etc. cannot survive without Calcium with Vit D3 supplementation. I think most people on these boards do not use supplements even with terrestrial caudates(myself included).

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Well doesn't that depend on how nutritious the food item being offered is? Surely you don't have to supplement earthworms?

fishkeeper said:

Considering Pleurodeles waltl has been found in caves and is by no means a subterranean caudate I think it is safe to say no caudate requires UV light.

In captivity though, UV lighting can be replaced with good supplementation and feeding even in animals that seem to require it(diurnal lizards, for example).

I've thought it interesting how most caudate keepers seem to be more lax with supplements than other amphibian/reptile keepers. Many state that terrestrial frogs etc. cannot survive without Calcium with Vit D3 supplementation. I think most people on these boards do not use supplements even with terrestrial caudates(myself included).

Click to expand...

Hi,

With regard to the uv lighting being replaced with good supplementation and feeding, I would point out that that only refers to the uv-B wavelengths. The uv-A wavelengths are also very important in stimulating activity - there are plenty of (admittedly mainly anecdotal) reports of dramatically different behaviour in basking reptile when given uv sources, as opposed to similar temperatures provided by heat sources which produce no significant uv. The first time you see an enclosure of basking lizards before and after provision of a uv source you'll be convinced by the difference. We must not forget uv-A.

The supplementation issue is very interesting. It certainly appears to be true that metabolic bone disease complex is far less frequently reported in caudates than anurans, although it does occur. While I suspect at least some of the difference is more due to lack of veterinary submission/reporting/investigation than actual, there may well be a difference. This is an area that does need more research. Despite many anecdotal diet/supplementation regimes that apparently work most of the time, I find there are usually exceptions, even within a given species - I've seen plenty of animals I would expect to be fine show drastic signs of metabolic bone disease, and vice versa.

Again, we must not forget other deficiencies - metabolic bone disease complex appears to be overwhelmingly the most common one seen in captive amphibians, but others can occur. But that's a different topic - sorry seem to be getting away from the uv issue here.

Anyway, just some thoughts.

Bruce.

Hi everyone, very interesting forum, just thought I would share what I got told and the outcomes on having a UV or not with newts.
I got my first Chinese fire-bellied newt a few years back I wasnt told anything by the breeder about needed a UV light and after asking he said I didnt need one for a juvenile, just adult. However, my newt contracted metabolic bone disease due to an insufficient amount of vit. D and I was then recomended by a vet to get a UV light. Unfortunately that newt had to be put down because of his condition. I was still keen to keep these amazing animals so I did get another newt and hoping that I had solved the problem by getting a UV all would be well. Unfortunately about 18 months after I got him he contracted these very wierd lumps down the sides of his body. I took him back to the vet where he was operated on, and survived at 0.8 g), and was told that the lumps were once again due to metabolic bone disease which was causing his spine was curved so much it was pushing his organs to either side of his body. He picked up remarkably after his operation but sadly he has reduced movement again as the lumps seem to have "come back". His life is now shorter but he is still active and feeding well so im just letting him be at the moment. So after all this I cannot say whether the UV was needed or not but the latest suggestion I have had is to add calcium to his diet which I would like to do with him to see if it helps in anyway as it may be too late but am sceptical sbout getting another newt as I do not want to watch another little one go through this aweful disease again as I cannot care for them and provid them with what they need to live properly.

Lydz

Hi all,

Im usually confined to the axolotl forum so i seldomly venture out. Please pardon me if i am ignorant in this area as i am a small animal vet and do not have much clinical experience with amphibians.

Jan has contacted me to share my findings on this topic. I am not sure if they are useful.

When i was in vet school (Sydney Uni), i was taught that axolotls require very low levels of UV exposure. i believe that it plays a small role in vit D metabolism (and hence prevent metabolic bone disease) as well as to regulate biorhythmns (circadian, diurnal, even breeding).

The general idea is that we have to advice the client to provide hiding places where the axies can retreat to for shade. From memory, i think just the usual aquarium lighting for plants will suffice as they do emit very low levels of both UVA and UVB irradiation. Only 6 hours per day of light (with presence of hiding spots) was necessary.

An exotic specialist vet i often refer my complex cases too also recommends the above in his practice newsletter.

I have emailed my three lecturers (who are exotic pet specialists/fellows) about this topic and shall post any updates here. I have also searched through cab abstract/ medline and zoological records for articles regarding the role of uv lights with axolotls and did find a few papers. Unfortunately i haven't had much time to go over all of them yet and some of them are in a foreign language but i suppose some of the members here can read them. Nontheless, here is the reference list.

Title: Review and new data on light sensitivity and non-visual orientation in Proteus anguinus, Calotriton asper and Desmognathus ochrophaeus (hypogean amphibian; Urodela).
Revue et nouvelles donnees sur la sensibilite a la lumiere et orientation non-visuelle chez Proteus anguinus, Calotriton asper et Desmognathus ochrophaeus (Amphibiens urodeles hypoges).
Author(s): Schlegel, Peter A.; Briegleb, Wolfgang; Bulog, Boris; et al.
Source: Bulletin de la Societe Herpetologique de France Volume: 118 Page(s): 17-47 Published: 2006

Title: The role of light for the early ontogenetical stages of the axolotl.
Author(s): Ephimov, M. I.
Source: C.R. Acad. Sci. URSS N.S. Volume: 83 Issue: 6 Page(s): 949-[952] Published: 1952

Effects of ultraviolet light and methoprene on survival and development of Rana pipiens.
Author(s): Ankley, G. T., Tietge, J. E., DeFoe, D. L., et al.
Source: Environmental Toxicology and Chemistry Volume: 17 Issue: 12 Pages: 2530-2542 Published: 1998

"Abstract: The objective of this study was to assess two stressors hypothesized as responsible for limb malformations in amphibians: methoprene, an insect growth regulator that, through interaction with the retinoic acid signalling system, could possibly cause limb deformities, and ultraviolet (UV) light. Northern leopard frogs (Rana pipiens) were exposed to several different concentrations of methoprene both in the absence and presence of UV light designed to mimic the UV wavelength spectrum present in sunlight. Exposures were initiated at early embryonic stages (newly fertilized eggs) and continued through emergence of the forelimbs of the frogs. At the highest methoprene concentration tested, both in the absence and presence of UV light, severe developmental effects were observed, with all organisms dying within 12 to 16 days of test initiation. However, exposure to the pesticide did not cause limb malformations. Irrespective of methoprene treatment, a very high percentage (~50%) of animals held under the UV light for 24 d developed hindlimb malformations. These malformations usually were bilateral and sometimes completely symmetrical, and consisted of missing limb segments and missing or reduced digits. A complete proximal to distal representation of the deficiencies occurred, ranging from missing or malformed femurs to the absence of single digits or digit segments. The developmental period of greatest sensitivity to UV light occurred during very early limb bud development, corresponding with formation of the apical ectodermal ridge. The significance of these findings in terms of deformed frogs in the field is uncertain. Although the deformity types observed (i.e., missing limb segments and digits) were similar to those seen in some field specimens, the UV light treatment did not cause the full range of malformations observed in animals from the field (e.g., supernumerary limbs, nonbilateral deformities). Furthermore, although the artificial light spectrum utilized mimicked the relative UV spectrum present in sunlight, it did not match full sunlight intensity, and did not accurately mimic visible wavelengths. Finally, the relationship of the UV light concentration used in the laboratory to that actually experienced by amphibians in the field is uncertain. Despite these questions, these findings suggest that UV light should be further considered as a plausible factor contributing to amphibian malformations in field settings."

Title: Survival of three species of anuran metamorphs exposed to UV-B radiation and the pathogenic fungus Batrachochytrium dendrobatidis.
Author(s): Garcia, T. S., Romansic, J. M., Blaustein, A. R.
Source: Diseases of Aquatic Organisms Volume: 72 Issue: 2 Pages: 163-169 Published: 2006

Abstract: When exploring the possible factors contributing to population declines, it is necessary to consider multiple, interacting environmental stressors. Here, we investigate the impact of 2 factors, ultraviolet radiation and disease, on the survival of anuran amphibians. Exposure to ultraviolet-B (UV-B) radiation increases mortality and results in various sub-lethal effects for many amphibian species. Infectious diseases can also negatively impact amphibian populations. In this study, we exposed metamorphic individuals (metamorphs) to both UV-B and Batrachochytrium dendrobatidis (BD), a fungal pathogen and cause of the disease chytridiomycosis, and monitored survival for 3 wk. We tested for possible interactions between UV-B and BD in 3 species: the Cascades frog Rana cascadae; the Western toad Bufo boreas; and the Pacific treefrog Hyla regilla. We found strong interspecific differences in susceptibility to BD. For example, R. cascadae suffered a large increase in mortality when exposed to BD; B. boreas also experienced mortality, but this effect was small relative to the R.cascadae response. H. regilla did not show any decrease in survival when exposed to either factor. No synergistic interactions between UV-B and BD were found for any of the test species. A previous study investigating the impact of BD on larval amphibians showed different species responses (Blaustein et al. 2005a). Our results highlight the importance of studying multiple life history stages when determining the impact of environmental stressors. The contrast between these 2 studies emphasizes how vulnerability to a pathogen can vary between life history stages within a single species.

Title: Spatial and temporal variability in the amount and source of dissolved organic carbon: implications for ultraviolet exposure in amphibian habitats.
Author(s): Brooks, P. D., O'Reilly, C. M., Diamond, S. A., et al.
Source: Ecosystems Volume: 8 Issue: 5 Pages: 478-487 Published: 2005

Abstract: The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1-2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain (R 2=0.39, F=25.71, P<0.0001) and across all parks in 2000 (R 2=0.44, F=38.25, P<0.0001). The relatively low R 2 values, however, reflect significant temporal and spatial variability in the specific attenuation per unit DOC. Fluorescence analysis of the fulvic acid DOC fraction (roughly 600-2,000 Daltons) indicated that the source of DOC significantly affected the attenuation of UV-B. Sites in Sequoia-Kings Canyon were characterized by DOC derived primarily from algal sources and showed much deeper UV -B penetration, whereas sites in Glacier and Rocky Mountain contained a mix of algal and terrestrial DOC-dominated sites, with more terrestrially dominated sites characterized by greater UV-B attenuation per unit DOC. In general, site characteristics that promoted the accumulation of terrestrially derived DOC showed greater attenuation of UV-B per unit DOC; however, catchment vegetation and soil characteristics, precipitation, and local hydrology interacted to make it difficult to predict potential exposure from DOC concentrations.

Title: The interactive effects of UV-B and insecticide exposure on tadpole survival, growth and development.
Author(s): Bridges, C. M., Boone, M. D.
Source: Biological Conservation Volume: 113 Issue: 1 Pages: 49-54 Published: 2003

Because declines within amphibian populations can seldom be attributed to a single cause, it is important to focus on multiple stressors, both natural and anthropogenic. Variables such as UV-B radiation and chemical contamination can interact with one another in ways that might not be predicted from single-factor studies. We exposed southern leopard frog (Rana sphenocephala) tadpoles to the insecticide carbaryl and varying intensities of UV-B radiation in artificial ponds and examined their effects on survival, size at metamorphosis, and the duration of the larval period. Tadpole survival to metamorphosis was positively influenced by UV-B intensity. Tadpoles in ponds exposed to carbaryl contained over three times more algae and yielded larger metamorphs than control ponds. Although previous laboratory studies have indicated carbaryl becomes more toxic in the presence of UV-B, we did not find such an effect, perhaps because of the protection afforded by dissolved organic carbon within the ponds. Our research emphasizes the importance of conducting field studies to more accurately predict what occurs under a natural setting.

Title: Spatial tests of the pesticide drift, habitat destruction, UV-B, and climate-change hypotheses for California amphibian declines.
Author(s): Davidson, C., Shaffer, H. B., Jennings, M. R.
Source: Conservation Biology Volume: 16 Issue: 6 Pages: 1588-1601 Published: 2002

Abstract:Wind-borne pesticides have long been suggested as a cause of amphibian declines in areas without obvious habitat destruction. In California, the transport and deposition of pesticides from the agriculturally intensive Central Valley to the adjacent Sierra Nevada is well documented, and pesticides have been found in the bodies of Sierra frogs. Pesticides are therefore a plausible cause of declines, but to date no direct links have been found between pesticides and actual amphibian population declines. Using a geographic information system, we constructed maps of the spatial pattern of declines for eight declining California amphibian taxa, and compared the observed patterns of decline to those predicted by hypotheses of wind-borne pesticides, habitat destruction, ultraviolet radiation, and climate change. In four species, we found a strong positive association between declines and the amount of upwind agricultural land use, suggesting that wind-borne pesticides may be an important factor in declines. For two other species, declines were strongly associated with local urban and agricultural land use, consistent with the habitat-destruction hypothesis. The patterns of decline were not consistent with either the ultraviolet radiation or climate-change hypotheses for any of the species we examined.

Title: Synergism between UV-B radiation and a pathogen magnifies amphibian embryo mortality in nature.
Author(s): Kiesecker, J. M., Blaustein, A. R.
Source: Proceedings of the National Academy of Sciences of the United States of America Volume: 92 Issue: 24 Pages: 11049-11052 Published: 1995

Previous research has shown that amphibians have differential sensitivity to ultraviolet-B (UV-B) radiation. In some species, ambient levels of UV-B radiation cause embryonic mortality in nature. The detrimental effects of UV-B alone or with other agents may ultimately affect amphibians at the population level. Here, we experimentally demonstrate a synergistic effect between UV-B radiation and a pathogenic fungus in the field that increases the mortality of amphibian embryos compared with either factor alone. Studies investigating single factors for causes of amphibian egg mortality or population declines may not reveal the complex factors involved in declines.

Regards

More articles below.

Title: Complex causes of amphibian population declines.
Author(s): Kiesecker, J. M., Blaustein, A. R., Belden, L. K.
Source: Nature (London) Volume: 410 Issue: 6829 Pages: 681-684 Published: 2001

Title: Declines of the California red-legged frog: climate, UV-B, habitat, and pesticides hypotheses.
Author(s): Davidson, C., Shaffer, H. B., Jennings, M. R.
Source: Ecological Applications Volume: 11 Issue: 2 Pages: 464-479 Published: 2001

Title: Ultraviolet vision and foraging in terrestrial vertebrates.
Author(s): Honkavaara, J., Koivula, M., Korpimaki, E., et al.
Source: Oikos Volume: 98 Issue: 3 Pages: 505-511 Published: 2002
(Discusses about amphibians as well)

Title: Effects of ultraviolet-B radiation and larval growth on toxicokinetics of waterborne bisphenol A in common frog (Rana temporaria) larvae.
Author(s): Koponen, P S, Tuikka, A, Kukkonen, J V K
Source: Chemosphere Volume: 66 Issue: 7 Pages: 1323-8 Published: 2007 (EPubDate 2006 28)

Abstract: In 1989, researchers discovered that amphibians, particularly frogs and toads from many parts of the world, appeared to be declining. In many ecosystems amphibians play a central role in ecosystem energy flow and nutrient cycling, and they act as keystone species. The recent increase in solar ultraviolet-B radiation (UVB, 280-320nm) has been thought to be one stressor responsible for the decline in amphibian populations. Along with other stressors, such as habitat destruction, anthropogenic influences and natural causes, UVB radiation could contribute to adverse effects among amphibians. Amphibians provide a good model for examining the effects of environmental stressors, because both lethal and sub-lethal responses are well documented in a range of studied xenobiotics in many species. In this experiment, the effects of UVB radiation on the accumulation and depuration kinetics of bisphenol A (BPA) were studied. Additionally, the accumulation was further modeled with correction for growth dilution. The results indicate that UVB radiation did not affect the toxicokinetics of BPA, and that the applied growth correction had only a negligible influence on the toxicokinetic estimations in this experiment. However, BCFs values calculated as k(u)/k(e) where closer to C(a)/C(w) calculated values when growth dilution was incorporated in the model. This method can be used in other experiments, where the growth dilution can affect toxicokinetic estimations.

Title: Combined exposure to ambient UVB radiation and nitrite negatively affects survival of amphibian early life stages.
Author(s): Macias, Guadalupe, Marco, Adolfo, Blaustein, Andrew R
Source: Sci Total Environ Volume: 385 Issue: 1-3 Pages: 55-65 Published: 2007 15 (EPubDate 2007 12)

Many aquatic species are sensitive to ambient levels of ultraviolet-B radiation (UVB) and chemical fertilizers. However, recent studies indicate that the interaction among multiple stressors acting simultaneously could be contributing to the population declines of some animal species. Therefore, we tested the potential synergistic effects between ambient levels of UVB and a contaminant, sodium nitrite in the larvae of two amphibian species, the common European toad Bufo bufo and the Iberian green frog Rana perezi. We studied R. perezi from both mountain and coastal populations to examine if populations of the same species varied in their response to stressors in different habitats. Both species were sensitive to the two stressors acting alone, but the interaction between the two stressors caused a multiplicative impact on tadpole survival. For B. bufo, the combination of UVB and nitrite was up to seven times more lethal than mortality for each stressor alone. In a coastal wetland, the combination of UVB and nitrite was four times more toxic for R. perezi than the sum of the effect on mortality for each stressor alone. One mg/L of nitrite killed half the population of R. perezi at Gredos Mountains at day 10 in the absence of UVB. In the presence of UVB, 50% of the tadpoles from the same experiment died at day 7. Similar toxic response were found for R. perezi in two highly contrasted environments suggesting this synergistic interaction can be a widespread phenomenon. The interaction of excess chemical fertilizers and manure with ambient UVB radiation could be contributing to the global decline of some amphibian species. We suggest that potential exposure to UVB radiation be accounted for when assessing water quality criteria regarding nitrite pollution.

Title: Chronic exposure of Rana pipiens tadpoles to UVB radiation and the estrogenic chemical 4-tert-octylphenol.
Author(s): Croteau, Maxine C, Martyniuk, Christopher J, Trudeau, Vance L, et al.
Source: J Toxicol Environ Health A Volume: 71 Issue: 2 Pages: 134-44 Published: 2008

Title: Global increases in ultraviolet B radiation: potential impacts on amphibian development and metamorphosis.
Author(s): Croteau, M C, Davidson, M A, Lean, D R S, et al.
Source: Physiol Biochem Zool Volume: 81 Issue: 6 Pages: 743-61 Published: 2008 Nov-Dec

Title: A meta-analysis of the effects of ultraviolet B radiation and its synergistic interactions with pH, contaminants, and disease on amphibian survival.
Author(s): Bancroft, Betsy A, Baker, Nick J, Blaustein, Andrew R
Source: Conserv Biol Volume: 22 Issue: 4 Pages: 987-96 Published: 2008 (EPubDate 2008 09)

Abstract: Human alterations to natural systems have resulted in a loss of biological diversity around the world. Amphibian population losses have been more severe than those of birds and mammals. Amphibian population declines are likely due to many factors including habitat loss, disease, contaminants, introduced species and ultraviolet-B (UVB) radiation. The effect of UVB, however, varies widely among species and can vary within populations of the same species or at different life-history stages. This variation has often led to opposing conclusions about how UVB affects amphibians. We used meta-analysis techniques to explore the overall effects of UVB radiation on survival in amphibians. We also used recently developed factorial meta-analytic techniques to quantify potential interactions between UVB radiation and other stressors on amphibians. Ultraviolet-B radiation reduced survival of amphibians by 1.9-fold compared with shielded controls. Larvae were more susceptible to damage from UVB radiation compared with embryos, and salamanders were more susceptible compared with frogs and toads. Furthermore, UVB radiation interacted synergistically with other environmental stressors and resulted in greater than additive effects on survival when 2 stressors were present. Our results suggest that UVB radiation is an important stressor in amphibians, particularly in light of potential synergisms between UVB and other stressors in amphibian habitats.

Title: Impact of UV-B exposure on amphibian embryos: linking species physiology and oviposition behaviour.
Author(s): Palen, Wendy J, Williamson, Craig E, Clauser, Aaron A, et al.
Source: Proc Biol Sci Volume: 272 Issue: 1569 Pages: 1227-34 Published: 2005 22

Title: Effects of ultraviolet radiation on toad early life stages.
Author(s): Little, Edward E, Calfee, Robin D, Fabacher, David L, et al.
Source: Environ Sci Pollut Res Int Volume: 10 Issue: 3 Pages: 167-72; discussion 172 Published: 2003

Title: UV-Absorbing compounds in the aqueous humor from aquatic mammals and various non-mammalian vertebrates.
Author(s): Ringvold, Amund, Anderssen, Erlend, Jellum, Egil, et al.
Source: Ophthalmic Res Volume: 35 Issue: 4 Pages: 208-16 Published: 2003 Jul-Aug

Title: Effects of ultraviolet-B radiation on behaviour and growth of three species of amphibian larvae.
Author(s): Pahkala, Maarit, Laurila, Anssi, Merila, Juha
Source: Chemosphere Volume: 51 Issue: 3 Pages: 197-204 Published:

Title: The role of the egg jelly coat in protecting Hyla regilla and Bufo canorus embryos from ultraviolet B radiation during development.
Author(s): Hansen, Lara J, Fabacher, David L, Calfee, Robin
Source: Environ Sci Pollut Res Int Volume: 9 Issue: 6 Pages: 412-6 Published: 2002

Title: Amphibian defenses against ultraviolet-B radiation.
Author(s): Blaustein, Andrew R, Belden, Lisa K
Source: Evol Dev Volume: 5 Issue: 1 Pages: 89-97 Published: 2003 Jan-Feb

Title: Assessment of the risk of solar ultraviolet radiation to amphibians. II. In situ characterzation of exposure in amphibian habitats.
Author(s): Peterson, Gregory S, Johnson, Lucinda B, Axler, Richard P, et al.
Source: Environ Sci Technol Volume: 36 Issue: 13 Pages: 2859-65 Published: 2002 1

Title: Effects of bisphenol A and artificial UVB radiation on the early development of Rana temporaria.
Author(s): Koponen, Petri S, Kukkonen, Jussi V K
Source: J Toxicol Environ Health A Volume: 65 Issue: 13 Pages: 947-59 Published: 2002

Title: Octylphenol and UV-B radiation alter larval development and hypothalamic gene expression in the leopard frog (Rana pipiens).
Author(s): Crump, Douglas, Lean, David, Trudeau, Vance L
Source: Environ Health Perspect Volume: 110 Issue: 3 Pages: 277-84 Published: 2002

Title: Ambient solar UV radiation causes mortality in larvae of three species of Rana under controlled exposure conditions.
Author(s): Tietge, J E, Diamond, S A, Ankley, G T, et al.
Source: Photochem Photobiol Volume: 74 Issue: 2 Pages: 261-8 Published: 2001

Title: Carry-over effects of ultraviolet-B radiation on larval fitness in Rana temporaria.
Author(s): Pahkala, M, Laurila, A, Merila, J
Source: Proc Biol Sci Volume: 268 Issue: 1477 Pages: 1699-706 Published: 2001 22

Title: The effects of solar UV-B radiation on embryonic mortality and development in three boreal anurans (Rana temporaria, Rana arvalis and Bufo bufo).
Author(s): Hakkinen, J, Pasanen, S, Kukkonen, J V
Source: Chemosphere Volume: 44 Issue: 3 Pages: 441-6 Published: 2001

Title: Ambient UV-B radiation causes deformities in amphibian embryos.
Author(s): Blaustein, A R, Kiesecker, J M, Chivers, D P, et al.
Source: Proc Natl Acad Sci U S A Volume: 94 Issue: 25 Pages: 13735-7 Published: 1997 9

Title: Spectral and polarization sensitivity of photocurrents of amphibian rods in the visible and ultraviolet.
Author(s): Palacios, A G, Srivastava, R, Goldsmith, T H
Source: Vis Neurosci Volume: 15 Issue: 2 Pages: 319-31 Published: 1998 Mar-Apr

Title: Characterization of an ultraviolet photoreception mechanism in the retina of an amphibian, the axolotl (Ambystoma mexicanum).
Author(s): Deutschlander, M E, Phillips, J B
Source: Neurosci Lett Volume: 197 Issue: 2 Pages: 93-6 Published: 1995 8

Title: Developmental responses of amphibians to solar and artificial UVB sources: a comparative study.
Author(s): Hays, J B, Blaustein, A R, Kiesecker, J M, et al.
Source: Photochem Photobiol Volume: 64 Issue: 3 Pages: 449-56 Published: 1996

Abstract—Many amphibian species, in widely scattered locations, currently show population declines and/or reductions in range, but other amphibian species show no such declines. There is no known single cause for these declines. Differential sensitivity to UVB radiation among species might be one contributing factor. We have focused on amphibian eggs, potentially the most UVB-sensitive stage, and compared their resistance to UVB components of sunlight with their levels of photolyase, typically the most important enzyme for repair of the major UV photoproducts in DNA, cyclobutane pyrimidine dimers. Photolyase varied 100-fold among eggs/oocytes of 10 species. Among three species–Hyla regilla, Rana cascadae, and Bufo boreas–for which resistance of eggs to solar UVB irradiance in their natural locations was measured, hatching success correlated strongly with photolyase. Two additional species, Rana aurora and Ambystoma gracile, now show similar correlations. Among the low-egg-photolyase species, R. cascadae and B. boreas are showing declines, and the status of A. gracile is not known. Of the two high-photolyase species, populations of H. regilla remain robust, but populations of R. aurora are showing declines. To determine whether levels of photolyase or other repair activities are affected by solar exposures during amphibian development, we have initiated an extended study of H. regilla and R. cascadae, and of Xenopus laevis, laboratory-reared specimens of which previously showed very low photolyase levels. Hyla regilla and R. cascadae tadpoles are being reared to maturity in laboratories supplemented with modest levels of UV light or light filtered to remove UVB wavelengths. Young X. laevis females are being reared indoors and outdoors. Initial observations reveal severe effects of both UVA and UVB light on H. regilla and R. cascadae tadpoles and metamorphs, including developmental abnormalities and high mortalities. Assays of photolyase levels in the skins of young animals roughly parallel previous egg/oocyte photolyase measurements for all three species.

Title: Synergism between UV-B radiation and a pathogen magnifies amphibian embryo mortality in nature.
Author(s): Kiesecker, J M, Blaustein, A R
Source: Proc Natl Acad Sci U S A Volume: 92 Issue: 24 Pages: 11049-52 Published: 1995

Title: UV repair and resistance to solar UV-B in amphibian eggs: a link to population declines?
Author(s): Blaustein, A R, Hoffman, P D, Hokit, D G, et al.
Source: Proc Natl Acad Sci U S A Volume: 91 Issue: 5 Pages: 1791-5 Published: 1994 1

Title: Influence of lighting conditions on toxicity and genotoxicity of various PAH in the newt in vivo.
Author(s): Fernandez, M, L'Haridon, J
Source: Mutat Res Volume: 298 Issue: 1 Pages: 31-41 Published: 1992

Title: A comparative study of the effects of egg rotation (gravity orientation) and UV irradiation on anuran vs. urodele amphibian eggs.
Author(s): Chung, H M, Malacinski, G M
Source: Differentiation Volume: 18 Issue: 3 Pages: 185-9 Published: 1981

The response of various anuran and urodele eggs to a brief rotation prior to first cleavage were observed. In all instances, the dorsal lip formed on the side of the egg which opposed gravity during the rotation. The ability of egg rotation to prevent the series of developmental abnormalities associated with UV irradiation of the uncleaved egg was also examined. Anuran and urodele eggs responded to those manipulations in a similar fashion. These results should facilitate future studies on the mechanisms involved in the establishment of the dorsal/ventral polarity of the amphibian egg.

A note on the mechanism of action of UV-irradiation of amphibian embryos.
Author(s): Duncan, C J
Source: Experientia Volume: 35 Issue: 6 Pages: 817-8 Published: 1979 15

Title: Further characterization of the effects of ultraviolet irradiation of the amphibian egg.
Author(s): Malacinski, G M, Chung, H M, Youn, B
Source: Experientia Volume: 34 Issue: 7 Pages: 883-4 Published: 1978 15

Title: Destruction of components of the neural induction system of the amphibian egg with ultraviolet irradiation.
Author(s): Malacinski, G M, Brothers, A J, Chung, H M
Source: Dev Biol Volume: 56 Issue: 1 Pages: 24-39 Published: 1977

Title: Distortions in amphibian development induced by ultraviolet-B enhancement (290-315 NM) of a simulated solar spectrum.
Author(s): Worrest, R C, Kimeldorf, D J
Source: Photochem Photobiol Volume: 24 Issue: 4 Pages: 377-82 Published: 1976

Title: Quantitative changes and ultrastructural alterations of the cornea in response to ultraviolet light. II. Effects of amphibia; elucidation of desmosomal structure and basement membrane synthesis.
Author(s): Margaritis, L H, Politof, T K, Koliopoulos, J X
Source: Tissue Cell Volume: 8 Issue: 4 Pages: 603-14 Published: 1976

Title: Repair of ultraviolet irradiation damage to a cytoplasmic component required for neural induction in the amphibian egg.
Author(s): Chung, H M, Malacinski, G M
Source: Proc Natl Acad Sci U S A Volume: 72 Issue: 4 Pages: 1235-9 Published: 1975

Title: Association of an ultraviolet irradiation sensitive cytoplasmic localization with the future dorsal side of the amphibian egg.
Author(s): Malacinski, G M, Benford, H, Chung, H M
Source: J Exp Zool Volume: 191 Issue: 1 Pages: 97-110 Published: 1975

Title: Correction of developmental abnormalities resulting from localized ultra-violet irradiation of an amphibian egg. 1.
Author(s): Malacinski, G M, Allis, C D, Chung, H M
Source: J Exp Zool Volume: 189 Issue: 2 Pages: 249-54 Published: 1974

Title: Photoreactivation of amphibian cells in culture.
Author(s): Regan, J D, Cook, J S, Lee, W H
Source: J Cell Physiol Volume: 71 Issue: 2 Pages: 173-6 Published: 1968

Title: An ultra-violet light method for producing haploid amphibian embryos.
Author(s): SELMAN, G G
Source: J Embryol Exp Morphol Volume: 6 Issue: 4 Pages: 634-7 Published: 1958

Title: Photo-recovery after ultraviolet radiation in amphibian larvae.
Author(s): BLUM, H F, MATHEWS, M M
Source: Biol Bull Volume: 99 Issue: 2 Pages: 330 Published: 1950

Generally from what i have read so far. My interpretation are as follows:

- Different amphibian species require differing amount of UV irradiation. They have different physiological adaptations.

- Even shade loving/nocturnal species (read the articles on axolotl) have physiological and anatomical adaptions to receive UV light (such as the eye to view the UV spectrum, presence of pineal gland which regulates biorhythmn etc.) Makes you wonder why they would have these adaptations if UV is not required.

- The role of UV is often closely linked to other variables like the presence of certain toxins, pathogens, pollutants. Thus a lot of the papers actually define that UV itself may not be the sole or main cause of amphibian decline but rather an interplay with other factors.

- Different stages of an amphibian (from egg to adult) have different sensitivity and requirements to UV. Appears that eggs have a UV protectant layer to protect against radiation damage which can cause malformation. Adults tend to be more resistant.

There are a lot of conflicting information from the various papers, i am not pro or against UV in amphibians as i do think it is indeed an area for more research. if anybody is interested in any of the articles, i do have most of them in full article form. Feel free to pm me.

Cheers.

Thanks for posting these references Ray - I thought you said you had a 'few' papers:happy:. This list must have taken quite some time to compile - your time is appreciated. Although many of these papers deal with toxicological, conservation and environmental research...I think they are pertinent as we discuss the topic of UV in amphibs, albeit most of this research is with anurans. I wish I could read French. The paper dealing with light sensitivity in three families of caudates looks most interesting.

Thanks also for your willingness to contact other exotic vets and to post their responses....this will lend nicely to the discussion.