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Andrew R Blaustein - One of the best experts on this subject based on the ideXlab platform.
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Virulence variation among strains of the emerging infectious fungus Batrachochytrium dendrobatidis (Bd) in multiple amphibian host species.
Diseases of Aquatic Organisms, 2017Co-Authors: Trang D. Dang, Catherine L. Searle, Andrew R BlausteinAbstract:Emerging infectious diseases have been documented in numerous plant and animal populations. The infectious disease amphibian chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is associated with global amphibian population declines. While much Bd-amphibian research has centered on response variation in hosts, a paucity of information exists on how variation in the pathogen, such as strain differences, affects infection dynamics. To examine how different Bd strains may differentially impact multiple hosts, we conducted laboratory experiments to measure 2 infection outcomes, viz. host survival and pathogen load, in 3 amphibian host species (Pacific treefrog, Western Toad, and Cascades frog) after exposure to 3 different Bd strains (an additional fourth Bd strain was tested in Toads only). Our results confirm that the infection response differs among host species. Western Toads experienced significant mortality, but Pacific treefrogs and Cascades frogs did not. Interestingly, our experiment also captured strain-dependent virulence variation but only in 1 host species, the Western Toad. Increased mortality was observed in 2 of the 4 Bd strains tested in this host species. Toads were also the only host species found to have variable pathogen load dependent on strain type; individuals exposed to the Panama strain harbored significantly higher loads compared to all other strains. These findings underscore the dynamic nature of Bd infection, showing that virulence can vary contingent on host and strain type. We highlight the importance of both host- and pathogen-dependent factors in determining overall infection virulence and show the need for in vivo testing to fully assess pathogenicity.
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induces severe limb malformations in Western Toads (Bufo boreas)
2015Co-Authors: Pieter T. J. Johnson, Jay Bowerman, Kevin B. Lunde, Ryan W. Haight, Andrew R BlausteinAbstract:Abstract: Widespread reports of malformed amphibians in North America have prompted investigations into the cause(s) and implications of the phenomenon. Recently, a trematode parasite (Ribeiroia ondatrae) was identified as the probable cause of hind-limb malformations in Pacific treefrogs (Hyla regilla) from California. We exposed a second anuran species, the Western Toad (Bufo boreas), to specific levels of R. ondatrae infection. In a dose-dependent manner, R. ondatrae infection induced high frequencies (40–85%) of severe limb malformations in surviving Toads. Survivorship declined significantly with increasing parasite exposure, falling to 42 % in the heaviest treatment. Larvae in control treatments exhibited normal development and low mortality levels. In contrast to previous experiments with R. ondatrae infection in treefrogs, cutaneous fusion was the predominant malformation among infected Toads in all treatments. In-fection also caused polymely (extra limbs; fore and hind), ectromely (missing limbs), polydactyly (extra digits), and a variety of additional limb malformations. Taken together, these results demonstrate that (i) the teratogenic effects of R. ondatrae are not limited to treefrogs, (ii) the spectrum of R. ondatrae-induced malformations is not confined to the hind limbs, and (iii) the frequency and composition of malformations resulting from infection may vary among am-phibian species. Finally, we review historical reports of limb abnormalities in the genus Bufo and discuss established and proposed causative agents, with emphasis on trematode infection and predation. Résumé: Les malformations chez les amphibiens sont de plus en plus signalées en Amérique du Nord; nous avon
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experimental evidence for american bullfrog lithobates catesbeianus susceptibility to chytrid fungus batrachochytrium dendrobatidis
Ecohealth, 2013Co-Authors: Stephanie S Gervasi, Tara Chestnut, Jenny Urbina, Rick A Relyea, Andrew R BlausteinAbstract:The emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), has been associated with global amphibian population declines and extinctions. American bullfrogs (Lithobates catesbeianus) are widely reported to be a tolerant host and a carrier of Bd that spreads the pathogen to less tolerant hosts. Here, we examined whether bullfrogs raised from eggs to metamorphosis in outdoor mesocosms were susceptible to Bd. We experimentally exposed metamorphic juveniles to Bd in the laboratory and compared mortality rates of pathogen-exposed animals to controls (non-exposed) in two separate experiments; one using a Bd strain isolated from a Western Toad and another using a strain isolated from an American bullfrog. We wanted to examine whether metamorphic bullfrogs were susceptible to either of these strains. We show that bullfrogs were susceptible to one strain of Bd and not the other. In both experiments, infection load detected in the skin decreased over time, suggesting that metamorphic bullfrogs from some populations may be inefficient long-term carriers of Bd.
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03. Susceptibility of newly-metamorphosed frogs to a pathogenic water mould ( Saprolegnia sp.)
Herpetological Journal, 2007Co-Authors: John M. Romansic, Elise M. Higashi, Kristin A. Diez, Andrew R BlausteinAbstract:Recent losses of worldwide biodiversity include population declines and extinctions in many amphibian populations. Many factors, including pathogens, are contributing to amphibian population declines. One pathogen, a water mould of the genus Saprolegnia, causes mortality in early life stages of amphibians and may contributeto the declines of specific amphibian populations. Most of our knowledge of how Saprolegnia affects amphibians comes from studies of embryos. The effects of Saprolegnia on post-metamorphic amphibians are poorly known. Therefore, in the laboratory, we investigated the susceptibility ofnewly-metamorphosedjuvenile amphibians to Saprolegnia in four frog species: Bufo boreas (Western Toad), Pseudacris regilla (Pacific treefrog), Rana aurora (red-legged frog) and R. cascadae (Cascades frog). We found that juvenile R. cascadae exposed to Saprolegnia had greater rates of mortality than unexposed controls. In the other species, survival was also lower in the Saprolegnia treatments compared with controls but these differences were not statistically significant. Combined effects of Saprolegnia in both embryonic and juvenile stages may make the populations of R. cascadae especially vulnerable.
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Survival of three species of anuran metamorphs exposed to UV-B radiation and the pathogenic fungus Batrachochytrium dendrobatidis.
Diseases of Aquatic Organisms, 2006Co-Authors: Tiffany S. Garcia, John M. Romansic, Andrew R BlausteinAbstract: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 spe- cies. 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.
Carlos Davidson - One of the best experts on this subject based on the ideXlab platform.
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the toxicity of glyphosate alone and glyphosate surfactant mixtures to Western Toad anaxyrus boreas tadpoles
Environmental Toxicology and Chemistry, 2015Co-Authors: Kim Vincent, Carlos DavidsonAbstract:Pesticide choice based on toxicity to nontarget wildlife is reliant on available toxicity data. Despite a number of recent studies examining the effects of glyphosate on amphibians, very few have aimed to understand the toxicological effects of glyphosate in combination with surfactants as it is commonly applied in the field. Land managers interested in making pesticide choices based on minimizing impacts to nontarget wildlife are hindered by a lack of published toxicity data. Short-term acute toxicity trials were conducted for glyphosate in the form of isopropylamine salt (IPA) alone and mixed with 2 surfactants: Agri-dex and Competitor with Western Toad (Anaxyrus [Bufo] boreas) tadpoles. Glyphosate IPA mixed with Competitor was 6 times more toxic than glyphosate IPA mixed with Agri-dex, and both mixtures were more toxic than glyphosate IPA alone. The median lethal concentrations reported for 24-h and 48-h exposures were 8279 mg/L (24 h) and 6392 mg/L (48 h) for glyphosate IPA alone; 5092 mg/L (24 h) and 4254 mg/L (48 h) for glyphosate IPA mixed with Agri-dex; and 853 mg/L (24 h) and 711 mg/L (48 h) for glyphosate IPA mixed with Competitor. The present study indicates that the toxicity of a tank mix may be greatly increased by the addition of surfactants and may vary widely depending on the specific surfactant. Environ Toxicol Chem 2015;9999:1–5. © 2015 SETAC
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The toxicity of glyphosate alone and glyphosate–surfactant mixtures to Western Toad (Anaxyrus boreas) tadpoles
Environmental Toxicology and Chemistry, 2015Co-Authors: Kim Vincent, Carlos DavidsonAbstract:Pesticide choice based on toxicity to nontarget wildlife is reliant on available toxicity data. Despite a number of recent studies examining the effects of glyphosate on amphibians, very few have aimed to understand the toxicological effects of glyphosate in combination with surfactants as it is commonly applied in the field. Land managers interested in making pesticide choices based on minimizing impacts to nontarget wildlife are hindered by a lack of published toxicity data. Short-term acute toxicity trials were conducted for glyphosate in the form of isopropylamine salt (IPA) alone and mixed with 2 surfactants: Agri-dex and Competitor with Western Toad (Anaxyrus [Bufo] boreas) tadpoles. Glyphosate IPA mixed with Competitor was 6 times more toxic than glyphosate IPA mixed with Agri-dex, and both mixtures were more toxic than glyphosate IPA alone. The median lethal concentrations reported for 24-h and 48-h exposures were 8279 mg/L (24 h) and 6392 mg/L (48 h) for glyphosate IPA alone; 5092 mg/L (24 h) and 4254 mg/L (48 h) for glyphosate IPA mixed with Agri-dex; and 853 mg/L (24 h) and 711 mg/L (48 h) for glyphosate IPA mixed with Competitor. The present study indicates that the toxicity of a tank mix may be greatly increased by the addition of surfactants and may vary widely depending on the specific surfactant. Environ Toxicol Chem 2015;9999:1–5. © 2015 SETAC
John S. Richardson - One of the best experts on this subject based on the ideXlab platform.
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Evidence for ecosystem engineering in a lentic habitat by tadpoles of the Western Toad
Aquatic Sciences, 2010Co-Authors: Sylvia L. R. Wood, John S. RichardsonAbstract:A number of aquatic organisms have demonstrated an ability to modulate sediment deposition in tropical and temperate stream systems, but little is known about the impact of similar benthic grazing processes in temperate pond systems. Using exclosure experiments in mesocosms, we used tadpoles of the Western Toad ( Anaxyrus boreas ) to investigate two questions: (1) can grazing activities of tadpoles of the Western Toad in ponds reduce sediment accrual on grazing surfaces (e.g. via bioturbation or ingestion); and (2) do these grazing activities contribute to enhanced periphyton biomass and chlorophyll a content of benthic matter. Mesocosms received pulses of fine sediment weekly over 8 weeks to simulate allochthonous surface inputs following rainstorms. Accumulated sediment and periphyton matter on exposed and grazing-restricted substrate surfaces were measured weekly. Tadpole grazing activity significantly reduced the standing stock of periphyton on open grazing surfaces by 80% in controls. Under sediment-additions, tadpoles effectively removed settled particulate matter from exposed grazing surfaces, but no corresponding increase in periphyton biomass was observed. These results suggest that tadpoles can impact the dynamics of sediment distribution in ponds as well as streams, providing support for a role as “ecosystem engineers” in these habitats.
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Impact of sediment and nutrient inputs on growth and survival of tadpoles of the Western Toad
Freshwater Biology, 2009Co-Authors: Sylvia L. R. Wood, John S. RichardsonAbstract:SUMMARY 1. Sediment and nutrient loading in freshwater systems are leading causes of aquatic habitat degradation globally. We investigated the impacts of fine-sediment and nutrient additions on the growth and survival of Western Toad (Bufo boreas) tadpoles and emergent metamorphs in mesocosm and exclosure experiments. 2. Mesocosm tanks received weekly pulses of fine sediments to create initial concentrations of 0, 130 and 260 mg L )1 of suspended sediment and either bi-weekly additions of nutrients (N = 160 l gL )1 ,P=1 0l gL )1 ) or no additions in a factorial design. Within mesocosms, tadpole exclosures allowed for quantification of tadpole grazing pressure on periphyton biomass, chlorophyll-a and sediment deposition. 3. Tadpoles receiving sediment additions experienced slower growth rates and reduced survival to metamorphosis, although no effects of treatment were detected on size at metamorphosis or time to metamorphosis. Nutrient additions also lowered survival, but had no impact on other measured parameters of tadpole fitness. Dissections and gut content analysis revealed that tadpoles ingested sediment in large quantities altering the proportion of the organic content of ingested food. 4. Together these results suggest that although sediment was readily consumed by tadpoles, its presence in the larval environment had an overall negative effect on tadpole growth and survival, although not as severe as predicted.
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Prevalence of the Chytrid Fungus (Batrachochytrium dendrobatidis) in Western Toads in SouthWestern British Columbia, Canada
Northwestern Naturalist, 2009Co-Authors: Isabelle Deguise, John S. RichardsonAbstract:Abstract The Western Toad (Anaxyrus boreas) is an IUCN red-listed species affected by habitat destruction and emerging infectious diseases. We tested for the chytrid fungus Batrachochytrium dendrobatidis (Bd) in a breeding population of Toads in southWestern British Columbia. Although the Toads showed no physical signs of infection, 28% of 32 Toads tested positive for Bd. To our knowledge, this study provides the first evidence of the chytrid fungus in a population of Western Toads in British Columbia. We also compared body condition to infection prevalence and found no significant relationship. Monitoring population trends and further testing for Bd prevalence are required throughout the province.
Kim Vincent - One of the best experts on this subject based on the ideXlab platform.
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the toxicity of glyphosate alone and glyphosate surfactant mixtures to Western Toad anaxyrus boreas tadpoles
Environmental Toxicology and Chemistry, 2015Co-Authors: Kim Vincent, Carlos DavidsonAbstract:Pesticide choice based on toxicity to nontarget wildlife is reliant on available toxicity data. Despite a number of recent studies examining the effects of glyphosate on amphibians, very few have aimed to understand the toxicological effects of glyphosate in combination with surfactants as it is commonly applied in the field. Land managers interested in making pesticide choices based on minimizing impacts to nontarget wildlife are hindered by a lack of published toxicity data. Short-term acute toxicity trials were conducted for glyphosate in the form of isopropylamine salt (IPA) alone and mixed with 2 surfactants: Agri-dex and Competitor with Western Toad (Anaxyrus [Bufo] boreas) tadpoles. Glyphosate IPA mixed with Competitor was 6 times more toxic than glyphosate IPA mixed with Agri-dex, and both mixtures were more toxic than glyphosate IPA alone. The median lethal concentrations reported for 24-h and 48-h exposures were 8279 mg/L (24 h) and 6392 mg/L (48 h) for glyphosate IPA alone; 5092 mg/L (24 h) and 4254 mg/L (48 h) for glyphosate IPA mixed with Agri-dex; and 853 mg/L (24 h) and 711 mg/L (48 h) for glyphosate IPA mixed with Competitor. The present study indicates that the toxicity of a tank mix may be greatly increased by the addition of surfactants and may vary widely depending on the specific surfactant. Environ Toxicol Chem 2015;9999:1–5. © 2015 SETAC
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The toxicity of glyphosate alone and glyphosate–surfactant mixtures to Western Toad (Anaxyrus boreas) tadpoles
Environmental Toxicology and Chemistry, 2015Co-Authors: Kim Vincent, Carlos DavidsonAbstract:Pesticide choice based on toxicity to nontarget wildlife is reliant on available toxicity data. Despite a number of recent studies examining the effects of glyphosate on amphibians, very few have aimed to understand the toxicological effects of glyphosate in combination with surfactants as it is commonly applied in the field. Land managers interested in making pesticide choices based on minimizing impacts to nontarget wildlife are hindered by a lack of published toxicity data. Short-term acute toxicity trials were conducted for glyphosate in the form of isopropylamine salt (IPA) alone and mixed with 2 surfactants: Agri-dex and Competitor with Western Toad (Anaxyrus [Bufo] boreas) tadpoles. Glyphosate IPA mixed with Competitor was 6 times more toxic than glyphosate IPA mixed with Agri-dex, and both mixtures were more toxic than glyphosate IPA alone. The median lethal concentrations reported for 24-h and 48-h exposures were 8279 mg/L (24 h) and 6392 mg/L (48 h) for glyphosate IPA alone; 5092 mg/L (24 h) and 4254 mg/L (48 h) for glyphosate IPA mixed with Agri-dex; and 853 mg/L (24 h) and 711 mg/L (48 h) for glyphosate IPA mixed with Competitor. The present study indicates that the toxicity of a tank mix may be greatly increased by the addition of surfactants and may vary widely depending on the specific surfactant. Environ Toxicol Chem 2015;9999:1–5. © 2015 SETAC
Joseph M Kiesecker - One of the best experts on this subject based on the ideXlab platform.
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Transfer of a Pathogen from Fish to Amphibians
Conservation Biology, 2001Co-Authors: Joseph M Kiesecker, Andrew R Blaustein, Cheri L. MillerAbstract:Ecological studies of exotic species focus primarily on how invaders directly affect particular resi- dent species. In contrast, little is known about the indirect effects of introduced species on native communi- ties, including how pathogens may be spread by introduced species. We provide evidence suggesting that in- troduced fish may serve as a vector for a pathogenic oomycete, Saprolegnia ferax , that has been associated with embryonic mortality of amphibians in the Cascade Mountains of Oregon, U.S.A. In laboratory experi- ments, mortality induced by S. ferax was greater in Western Toad ( Bufo boreas ) embryos exposed directly to hatchery-reared rainbow trout ( Oncorhynchus mykiss ) experimentally infected with S. ferax and hatchery- reared trout not experimentally infected than in control embryos. Embryos also developed significant S. ferax infections when raised on soil that was exposed to trout experimentally infected with S. ferax . Furthermore, Toad embryos exposed to S. ferax isolated from sites where Saprolegnia outbreaks are common experienced higher mortality than embryos exposed to S. ferax isolated from sites where Saprolegnia outbreaks have not occurred. Given the widespread practice of introducing hatchery-reared fishes, we suggest that fish used in stocking programs could be an important vector for diseases responsible for amphibian losses. Transferencia de un Patogeno de Peces a Anfibios Resumen: Los estudios ecologicos de especies exoticas estan enfocados principalmente en el efecto de los in- vasores sobre ciertas especies residentes. En contraste, se sabe poco de los efectos de especies introducidas so- bre comunidades nativas, incluyendo la dispersion de patogenos por las especies introducidas. Proporciona- mos evidencia que sugiere que peces introducidos pueden ser el vector de un oomiceto patogeno, Saprolegnia ferax , que se ha asociado con la mortalidad embrionaria de anfibios en las montanas Cascade de Oregon, E.U.A. En experimentos de laboratorio, la mortalidad inducida por S. ferax fue mayor en embriones de sapo ( Bufo boreas ) expuestos directamente a truchas arco iris ( Oncorhynchus mykiss ) criadas en granjas y experi- mentalmente infectadas con S. ferax y con truchas no infectadas experimentalmente que en los embriones control. Los embriones tambien desarrollaron infecciones significativas con S. ferax cuando fueron criados en sitios expuestos a truchas infectadas experimentalmente con S. ferax . Mas aun, los embriones expuestos a S. ferax aislado de sitios con brotes comunes de Saprolegnia , presentaron mayor mortalidad en comparacion con embriones expuestos a S. ferax aislado de sitios en los que no han ocurrido brotes de Saprolegnia . Dada la introduccion generalizada de peces criados en granjas, sugerimos que los peces utilizados en esos programas pudieran ser vectores importantes de enfermedades responsables de la perdida de anfibios.
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the use of chemical cues in predator recognition by Western Toad tadpoles
Animal Behaviour, 1996Co-Authors: Joseph M Kiesecker, Douglas P Chivers, Andrew R BlausteinAbstract:Abstract Western Toad, Bufo boreas , tadpoles were collected from a lake in the Cascade Mountains of central Oregon, where they occur in sympatry with backswimmers, Notonecta spp., giant waterbugs, Lethocerus americanus , common garter snakes, Thamnophis sirtalis , roughskin newts, Taricha granulosa and rainbow trout, Oncorhynchus mykiss . Backswimmers, waterbugs and snakes prey on Toad tadpoles. Newts and trout are potential tadpole predators, but they find Toad tadpoles unpalatable. In laboratory tests, groups of tadpoles responded with anti-predator behaviour when exposed to live backswimmers, waterbugs and snakes, but not when exposed to either newts or trout. In subsequent tests, when only chemical cues from the stimulus animals were presented, the Toad tadpoles again responded to backswimmers, waterbugs and snakes, but not to either newts or trout. When tests were conducted using only visual cues, tadpoles did not respond with anti-predator behaviour to any of the heterospecifics with the possible exception of garter snakes. These results show that Western Toad tadpoles can distinguish between predatory and non-predatory heterospecifics with which they co-occur, and that predator recognition by Toad tadpoles is primarily based on chemical cues.
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UV repair and resistance to solar UV-B in amphibian eggs: a link to population declines?
Proceedings of the National Academy of Sciences of the United States of America, 1994Co-Authors: Andrew R Blaustein, P D Hoffman, Susan C. Walls, D Grant Hokit, Joseph M Kiesecker, John B. HaysAbstract:The populations of many amphibian species, in widely scattered habitats, appear to be in severe decline; other amphibians show no such declines. There is no known single cause for the declines, but their widespread distribution suggests involvement of global agents--increased UV-B radiation, for example. We addressed the hypothesis that differential sensitivity among species to UV radiation contributes to these population declines. We focused on species-specific differences in the abilities of eggs to repair UV radiation damage to DNA and differential hatching success of embryos exposed to solar radiation at natural oviposition sites. Quantitative comparisons of activities of a key UV-damage-specific repair enzyme, photolyase, among oocytes and eggs from 10 amphibian species were reproducibly characteristic for a given species but varied > 80-fold among the species. Levels of photolyase generally correlated with expected exposure of eggs to sunlight. Among the frog and Toad species studied, the highest activity was shown by the Pacific treefrog (Hyla regilla), whose populations are not known to be in decline. The Western Toad (Bufo boreas) and the Cascades frog (Rana cascadae), whose populations have declined markedly, showed significantly lower photolyase levels. In field experiments, the hatching success of embryos exposed to UV radiation was significantly greater in H. regilla than in R. cascadae and B. boreas. Moreover, in R. cascadae and B. boreas, hatching success was greater in regimes shielded from UV radiation compared with regimes that allowed UV radiation. These observations are thus consistent with the UV-sensitivity hypothesis.
