Damage to the rainbow trout (Oncorhyncus mykiss) lens following an acute dose of UVB

Integrated histopathological lesion (IHL) analysis - a histopathological tool for the evaluation of UV-B exposure on the gill, liver and intestine of Catla catla

The present study aimed to analyse the integrated histopathological lesions (IHLs) of the gill, liver and intestine of Catla catla exposed to the different doses of UV-B radiation. Gill exhibited the lesions like hypertrophy, hyperplasia, vacuolation, fusion of the gill filaments, rupture in the gill lamellae, epithelial cell lifting and necrosis. The UV-B-exposed liver of Catla showed the lesions like the degeneration of nucleus, the disarrangement of hepatocytes, sinusoidal vacuolation, epitheliod histiocyst, hepatocellular adenoma, exocrine adenoma, cyst formation and diffused epithelial necrosis (DEN). UV-B-exposed intestine showed the lesions like the distortion of columnar epithelial cells (CECs), distortion in lamina propria (LP), disruption in brush border (BB), vacuolation in LP, the presence of submucosal mass (SM), the degeneration of nucleus, the presence of tactoid bodies, the presence of aschoff nodules and metatypical cell carcinoma. These histopathological alterations can be considered as the main blocking alterations of the growth and absorption as well as the final production of fish which can cause a serious loss in total yield to fish farmers which can interrupt the profitable economical production of fish.

Evaluation of cataract formation in fish exposed to environmental radiation at Chernobyl and Fukushima

Recent studies apparently finding deleterious effects of radiation exposure on cataract formation in birds and voles living near Chernobyl represent a major challenge to current radiation protection regulations. This study conducted an integrated assessment of radiation exposure on cataractogenesis using the most advanced technologies available to assess the cataract status of lenses extracted from fish caught at both Chernobyl in Ukraine and Fukushima in Japan. It was hypothesised that these novel data would reveal positive correlations between radiation dose and early indicators of cataract formation. The structure, function and optical properties of lenses were analysed from atomic to millimetre length scales. We measured the short-range order of the lens crystallin proteins using Small Angle X-Ray Scattering (SAXS) at both the SPring-8 and DIAMOND synchrotrons, the profile of the graded refractive index generated by these proteins, the epithelial cell density and organisation and finally the focal length of each lens. The results showed no evidence of a difference between the focal length, the epithelial cell densities, the refractive indices, the interference functions and the short-range order of crystallin proteins (X-ray diffraction patterns) in lens from fish exposed to different radiation doses. It could be argued that animals in the natural environment which developed cataract would be more likely, for example, to suffer predation leading to survivor bias. But the cross-length scale study presented here, by evaluating small scale molecular and cellular changes in the lens (pre-cataract formation) significantly mitigates against this issue.

Time dependent ultrastructural alterations on the skin, eye, barbel and fins of the spawn of Clarias batrachus (Linn. 1758) exposed to UV-B radiation

Present study highlighted the ultramicroscopic (SEM) alterations of the skin, eye, barbel, and fins of spawn of an air-breathing teleost (Clarias batrachus, Linn. 1758) induced by UV-B radiation (280-320 nm) at a dose (@4.07 × 10^-20J/photon/m²) under the time-frame of 5, 10 and 15 min/d in the laboratory condition for the periods of 5 and 10 days. Limnological parameters revealed no significant changes throughout the period of experimentation which were measured by PCS Testr 35 Multi-Parameter. Morphometric analysis revealed that during the extended exposure period of 10 days the spawn size and weight were reduced as analysed through Specific Growth Rate (SGR). SGR values in terms of weight for 5 and 10 days under 3 time-frames were 17.12%, 12.52%, 11.46% and 9.09%, 6.43%, 6.09% respectively, which revealed a declined trend along with the exposure days. In the skin of C. batrachus, the compact regular orientation of the stratified epithelial cells and mucous cells became distorted and the microridges and double-ridged structures showed destruction and fragmentations. The body striations and microfolds became shrinked and swollen and finally degenerated to form a mass. The distribution of mucous cells throughout the epidermis was disorganised and releasing secretory contents on the surface through small pores. Appearance of huge quantity of biogenic semi-hexagonal plate like crystals (guanine platelets) on the skin surface of the body was the most significant observations during UV-B radiation. In the developmental phases the eyeball showed shrinkage loosing normal regular concave structure and to become a dome-shaped one. The supportive connective infoldings became loosened. The choroid coat displayed deformities and the iris deformed the pupil. The fibroblast on the epithelium and melanocytes depicted dispersed arrangement. The pairs of ventral barbels near the mouth depicted the presence of taste buds that became severely damaged exposing the sensory as well as neuroepithelial cells. Compact regular arrangement of the SECs was completely destroyed leaving long and deep channels inbetween them; the disintegrated concentric MRs also showed a mass.

Effects of low levels of ultraviolet radiation on antioxidant mechanisms of Japanese Medaka (Oryzias latipes)

Extreme weather events like drought are expected to increase with climate change, which will increase exposure of freshwater fish to ultraviolet (UV) radiation. Compared to fully grown adult fish, fish in early life stages are more susceptible to UV radiation due to the lack of well-developed pigmentation. Even though several studies have described affectation of fish health after exposure to UV radiation, most of the studies have used intensities that are only found on the surface of the earth crust or at shallow depths in water bodies, and little is known about impacts of weaker UV radiation, which can be found in deep water. This study showed effects on the antioxidant system of Japanese Medaka after 7 days of exposure to very low intensities of UV radiation, levels that can be found at deep locations in lakes and rivers. Exposure to UV radiation (UVA: 360.1 ± 18.4 μW cm^-2 for a dose of 21.6 ± 1.2 mJ cm^-2 min^-1, and UVB: 6.3 ± 0.5 μW cm^-2 for a dose of 0.38 ± 0.03 mJ cm^-2 min^-1) caused a reduction in the catalase activity (over 50%) and enhanced oxidative damage to lipids. Results of this study showed that environmentally relevant, low levels of UV radiation affect mechanisms by which fish deal with enhanced production of reactive oxygen species and oxidative damage. The results raise concerns about early life stages of fish under scenarios of increased exposure to solar light, such as in tropic regions or during summer in temperate regions.

UV radiation impacts body weight, oxygen consumption, and shelter selection in the intertidal vertebrate Girella laevifrons

The amount of ultraviolet (UV) radiation reaching the earth's surface has increased due to ozone layer depletion, and this fact represents an opportunity to evaluate the physiological and behavioral responses of animals to this global-scale stressor. The transitory fish Girella laevifrons inhabits pools in the upper intertidal zone, which is characterized by exposure to a wide range of stressors, including UV radiation. We documented the field magnitude and the impact of UV radiation on oxygen consumption, body mass variations, and shelter (rocky and algae) selection by G. laevifrons. UV-exposed animals showed increased oxygen consumption, slower body weight increase, and active rocky shelter selection. Control fish showed increased body weight and no evident shelter selection. The results indicated that UV exposure affects fish energetic balance and habitat selection to favor greater protection against radiation. Increased UV exposure in transitory intertidal animals at levels observed in upper intertidal pools may alter the residency time of fish before leaving for the subtidal zone. Therefore, UV-induced energetic changes may determine animal performance and ontogenetic physiological itineraries, whereas shelter quality might determine habitat use.

Effect of UV radiation on habitat selection by Girella laevifrons and Graus nigra (Kyphosidae)

The effect of UV radiation on habitat use of two species of intertidal fishes that inhabit the same pools but exhibit different activity levels and diets was measured: the highly active omnivorous Girella laevifrons and the cryptic carnivorous Graus nigra. Individuals of each species were acclimated to a tank divided in three sections with different illumination; no light (NL), ultraviolet light (UV) and white light (WL), and the time spent and number of visits to each section were recorded. Although both species preferred the NL section, G. laevifrons spent more time in UV and less time in WL compared with G. nigra; G. laevifrons also displayed higher number of visits to UV, suggesting a different tendency in space use in response to UV exposure in intertidal fishes.

Effects of environmental and artificial UV-B radiation on freshwater prawn Macrobrachium olfersi embryos

The recent decrease of the stratospheric ozone has resulted in an increase of ultraviolet-B (UV-B) radiation reaching the Earth's surface. In freshwater ecosystems with transparent water, UV-B rays easily penetrate and potentially cause harmful effects to organisms. In this study, embryos of the prawn Macrobrachium olfersi were used to evaluate the impact of UV-B rays in freshwater environments. We observed three groups of embryos: the first was to assess whether UV-B radiation produced morphological defects and/or biochemical impairments in the laboratory. The second was to check whether embryos with the same impairments as those observed in the laboratory were found in their environment, under natural solar radiation. The third group was the non-irradiated control. The embryos irradiated with 310 mW cm(-2) UV-B for 30 min showed morphological alterations similar to those observed in embryos from the environmental control group. The most important effects of the UV-B radiation observed in M. olfersi embryos were morphological (1.2% of the total number of embryos from the environment and 2.8% of the total number of irradiated embryos), pigmentation changes in the eyes (78.0% of the total number of embryos from the environment and 98.9% of the total number of irradiated embryos), and disruption of the chromatophores (46.9% of the total number of embryos from the environment and 95.5% of the total number of irradiated embryos). We also observed an increase in egg volume, which was accompanied by a significant increase in water content in UV-B irradiated groups when compared with aquaria control embryos. In addition, a significant decrease in the mitotic index in eggs exposed to UV-B radiation was detected (0.17 for the embryos from the aquaria control, 0.10 for the embryos of the environmental control, and 0.04 for the irradiated groups). The low levels of NPSH and high levels of TBARS indicated that UV-B rays directly compromised the antioxidant function of the embryonic cells, leading to oxidative stress. Our combined morphological and biochemical analyses revealed important effects induced by UV-B on M. olfersi embryos, and the results suggest that the recent changes in global conditions may have injurious effects, at least on the embryos of freshwater prawns.

Ultraviolet influence on catalase activity and mineral content in eyeballs of gibel carp (Carassius auratus gibelio)

UV radiation present in the environment may induce several eye disorders including inflammation and cataract. The aim of this work was to study catalase activity and Mg, Cu, Ca and Zn contents in the eyeballs of gibel carp exposed to ecologically relevant doses of UV radiation (0.09 kJ/m2 for UV-A and 0.98 kJ/m2 for UV-B) simulated in laboratory conditions. Ultraviolet exposure resulted in significant reduction of catalase activity in the eyeballs of tested fish. Reductions in Mg, Cu and Ca contents after UV exposure were also observed. The differences in Mg and Cu levels between control and UV exposed animals were statistically significant, whereas the reduction of Ca level was insignificant. Zinc level in the eyeballs of UV-exposed fish was significantly higher than in non-irradiated specimens. The results suggest that ultraviolet radiation affects prooxidant/antioxidant balance and Mg, Cu, Zn contents in the eyes of fish living in shallow habitats. These may lead to cataract formation.

Ontogenetic changes and environmental effects on ocular transmission in four species of coral reef fishes

Filtration by the humors, cornea and lens limits the spectrum of light available for vision as blocking compounds prevent some wavelengths from reaching photo-sensitive cells of the retina. The visual ecology of fishes is dependent upon factors changing with size and/or habitat. We predicted that ontogeny and habitat depth would affect ocular transmission for four fishes, Mulloidichthys flavolineatus, Parupeneus multifasciatus, Acanthurus triostegas, and Naso lituratus. We measured ocular transmission in specimens from a range of sizes (juvenile-adult) and capture depths (<3-37 m), and used the wavelength (nm) where transmission was reduced 50% as our comparative measure (T(50)). We modeled lens transmission varying pigment concentrations and pathlength, and compared predicted versus measured results. P. multifasciatus, M. flavolineatus, and N. lituratus showed a significant increase in short-wavelength blocking with size. A. triostegas were constant across sizes, and showed a slight but significant effect with depth. Comparisons of predicted versus observed transmission values suggest that pigment concentrations are held constant with age for all species, but species- and family-level differences emerge. The accumulation of blocking compounds in ocular tissues is a contributing means for balancing the costs and benefits of admitting short-wavelength radiation to the retina.

Optical properties of rainbow trout lenses after in vitro exposure to polycyclic aromatic hydrocarbons in the presence or absence of ultraviolet radiation

The optical properties of rainbow trout lenses were investigated after in vitro exposure to polycyclic aromatic hydrocarbons (PAHs) and ultraviolet (UV) irradiation, both because PAHs frequently contaminate aquatic environments and because UV exposure has generally increased with the decline of the ozone layer. Lenses were exposed to UV irradiation for 12 hr while immersed in culture medium. UV irradiation, with or without the presence of PAHs, was accomplished with one UVA and one UVB photoreactor lamp to yield a photon fluence rate of 9.27 micromol m(-2)s(-1)UVA (UVA:UVB 10.8, radiant exposure of 13.4 Jcm(-1)). Individual PAHs studied were fluorene, fluoranthene and benzo(a)pyrene. In addition, lenses were exposed to a solution of creosote, a wood preservative used in the aquatic environment that contains many PAHs. All PAH exposures, including creosote, were carried out either in the dark or concurrently with UV irradiation. A scanning laser monitor system was used to evaluate the optical properties of lenses for up to 236 hr after the UV/PAH treatments. Mean focal length variability (FLV) increased with time after concurrent exposure to UV irradiation and high concentrations of either fluoranthene (4900 n m), benzo(a)pyrene (265 n m) or creosote (70 microg ml(-1)), with FLV values ranging from, 0.21-0.41, 0.21-0.64 and 0.15-0.22 mm, respectively, 72 hr after termination of the UV/PAH treatment. UV irradiation alone or exposure to PAHs in the dark brought about no changes in the optical properties of lenses. Also, fluorene in the presence or absence of UV had no effect, even at concentrations as high as 128 microm. Lenses were also unchanged by 12 hr exposures in the dark to solutions of either fluorene, fluoranthene, benzo(a)pyrene or creosote that had been previously UV irradiated for 12 hr. This meant that photomodified products of the individual PAHs or creosote were not cataractogenic and emphasized that simultaneous exposure to UV and PAHs or creosote was necessary for the increased FLV. The results point for the first time to an interaction between UV irradiation and PAHs as a potential contributing factor to cataract formation in fish.

Solar pruning of retinal rods in albino rainbow trout

Morphology of the central retina and scotopic visual sensitivity were compared in juvenile albino and normally pigmented rainbow trout living under natural and reduced daylight. Outdoor albinos avoided exposing their eyes to direct sunlight, whereas normals were indifferent to it. After 4 months outdoors (approximately 10,000 lux in albinos, approximately 100,000 lux in normals), albinos had severely truncated or missing rod outer segments (ROS) and some missing rod ellipsoids, but normal numbers of photoreceptor nuclei and fully intact cones. Albino estimated ROS volume was only 7.1% of normal in July, but increased to 20% by the following February, mainly via an increase in numbers of ROS. However, in albinos moved indoors October 7 and exposed to 10-30 lux ambient daylight, both the number and length of ROS increased significantly, with estimated ROS volume reaching 95% of normal by 34 days. Albinos generally had more phagosomes (approximately 3 x normal) and more macrophages (approximately 2 x normal) in their outer retina. An optomotor reflex was used to define the effect of ROS volume on the ability to respond visually during dark adaptation. In July, albinos and normals from outdoor raceways (3 months) or indoor raceways (35 days) showed equal sensitivity after first being placed in darkness, but after 1 h in darkness, outdoor albinos with 6% of normal ROS volume were 2.0 log units less sensitive than indoor or outdoor normals, whereas indoor albinos with 53% of normal ROS volume were only 0.7 log units less sensitive. This verifies that most rod cell bodies of albino trout can persist without functional ROS in indirect sunlight, and can regrow functional outer segments in dim daylight. This finding is distinct from the extensive retinal light damage observed in albino rats exposed to more moderate cyclic light, in which entire rod cells degenerate early on.

Lenticular changes in rainbow trout following chronic exposure to UV radiation

Rainbow trout (Onchorynchus mykiss) were exposed to broad band ultraviolet irradiation for a period of 205 days with a 12h/12h on/off cycle. Total radiant exposure was 8.279 x 10(3) J cm-2 of UVA and 1.050 x 10(2) J cm-2 of UVB. Control fish were maintained under UVB-free and blue-free conditions. Quantitative and qualitative evaluation of the teleost crystalline lenses involved photo slitlamp biomicroscopy, dark-field stereomicroscopy and automated scanning laser monitoring. More cataractous changes including discrete anterior subcapsular and 'doughnut' opacities, and peri-nuclear haze were recorded in the lenses of the fish that received chronic UV exposure. However, no significant differences were found in focal lengths and scatter within the sensitivity of the instrumentation. These results support the hypothesis that chronic exposure to ambient levels of ultraviolet radiation is cataractogenic.

Optical effects of UV-A and UV-B radiation on the cultured bovine lens

The effects of repeated exposures to UV-A (335 nm) and UV-B (305 nm) radiation on the crystalline lens were studied by treating cultured bovine lenses daily or weekly. The effects of irradiation on lens optical quality were monitored using an automated scanning laser system that records both relative transmittance and focal length across the lens. Relatively low radiant exposures of UV-B were used (0.06, 0.03, 0.01 J/cm2) compared to UV-A (1.44 J/cm2). In total, 38 treated lenses and 32 controls were cultured for times ranging from 400-1000 hours. Results indicate that this range of UV-B exposure may represent the threshold for in vitro UV-B induced opacification. Lenses treated weekly with 0.06 J/cm2 UV-B showed a significant decrease in transmittance compared to controls 69 hours after the first treatment and an increase in focal length variability. The ability of the lens to repair itself, as found in a previous single dose study, was absent after repeated doses. Lenses exposed daily to 0.03 and 0.01 J/cm2 UV-B showed no significant change in transmittance or focal length variability compared to controls. Daily exposure to 1.44 J/cm2 UV-A resulted in no significant change in transmittance or focal length variability compared to controls.