Effect of UVB radiation on the survival, feeding, and egg production of the brackish-water copepod, Sinocalanus tenellus, with notes on photoreactivation

We examined the effects of UVB radiation on hatching success of eggs, survival of various naupliar and copepodite stages, and feeding and egg production of adult females of the brackish-water copepod, Sinocalanus tenellus, by exposure to varying doses of UVB irradiance in the laboratory. Artificial UVB radiation resulted in an increased mortality of eggs, nauplii and copepodites with increasing UVB doses. UVB induced damage was stage-specific with eggs being most susceptible (LD₅₀= 4.1 kJ m^–2 ) and adult females being least susceptible (LD₅₀= 16.7 kJ m^–2). Effects on feeding and egg production of adult females were significantly evident at UVB doses higher than 11.0 kJ m^–2 and 7.0 kJ m^–2, respectively. We also examined the photorepair response of eggs and various developmental stages in simultaneous irradiation of UVB and enhanced PAR. With enhanced PAR there was a considerable recovery against UVB damage, being higher for younger animals than older ones. In nature, however, solar UVB radiation may rarely cause appreciable damage to S. tenellus population due to optically high attenuation properties of their habitat waters.     

<Emphasis Type="Italic">Iridaea cordata</Emphasis> (Gigartinales,Rhodophyta): responses to artificial UVB radiation

The effects of UVB radiation on the different developmental stages of the carrageenan-producing red alga Iridaea cordata were evaluated considering: (1) carpospore and discoid germling mortality; (2) growth rates and morphology of young tetrasporophytes; and (3) growth rates and pigment content of field-collected plant fragments. Unialgal cultures were submitted to 0.17, 0.5, or 0.83 W m⁻² of UVB radiation for 3 h per day. The general culture conditions were as follows: 12 h light/12 h dark cycles; irradiance of 55 μmol photon^.per square meter per second; temperature of 9 ± 1°C; and seawater enriched with Provasoli solution. All UVB irradiation treatments were harmful to carpospores ( 0.17  \textW \textm ^{- 2} = 40.9 ±6.9% 0.17\;{\text{W}}\,{{\text{m}}^{ - 2}} = 40.9 \pm 6.9\% , 0.5  \textW \textm ^{- 2} = 59.8 ±13.4% 0.5\;{\text{W}}\,{{\text{m}}^{ - 2}} = 59.8 \pm 13.4\% , 0.83  \textW \textm ^{- 2} = 49 ±17.4% 0.83\;{\text{W}}\,{{\text{m}}^{ - 2}} = 49 \pm 17.4\% mortality in 3 days). Even though the mortality of all discoid germlings exposed to UVB radiation was unchanged when compared to the control, those germlings exposed to 0.5 and 0.83 W m⁻² treatments became paler and had smaller diameters than those cultivated under control treatment. Decreases in growth rates were observed in young tetrasporophytes, mainly in 0.5 and 0.83 W m⁻² treatments. Similar effects were only observed in fragments of adult plants cultivated at 0.83 W m⁻². Additionally, UVB radiation caused morphological changes in fragments of adult plants in the first week, while the young individuals only displayed this pattern during the third week. The verified morphological alterations in I. cordata could be interpreted as a defense against UVB by reducing the area exposed to radiation. However, a high level of radiation appears to produce irreparable damage, especially under long-term exposure. Our results suggest that the sensitivity to ultraviolet radiation decreases with increased algal age and that the various developmental stages have different responses when exposed to the same doses of UVB radiation.     

THE EFFECTS OF ULTRAVIOLET‐B RADIATION ON ANTARCTIC SEA‐ICE ALGAE1

The impacts of ultraviolet‐B radiation (UVB) on polar sea‐ice algal communities have not yet been demonstrated. We assess the impacts of UV on these communities using both laboratory experiments on algal isolates and by modification of the in situ spectral distribution of the under‐ice irradiance. In the latter experiment, filters were attached to the upper surface of the ice so that the algae were exposed in situ to treatments of ambient levels of PAR and UV radiation, ambient radiation minus UVB, and ambient radiation minus all UV. After 16 d, significant increases in chl a and cell numbers were recorded for all treatments, but there were no significant differences among the different treatments. Bottom‐ice algae exposed in vitro were considerably less tolerant to UVB than those in situ, but this tolerance improved when algae were retained within a solid block of ice. In addition, algae extracted from brine channels in the upper meter of sea ice and exposed to PAR and UVB in the laboratory were much more tolerant of high UVB doses than were any bottom‐ice isolates. This finding indicates that brine algae may be better adapted to high PAR and UVB than are bottom‐ice algae. The data indicate that the impact of increased levels of UVB resulting from springtime ozone depletion on Antarctic bottom‐ice communities is likely to be minimal. These algae are likely protected by strong UVB attenuation by the overlying ice and snow, by other inorganic and organic substances in the ice matrix, and by algal cells closer to the surface.     

Latitudinal variation in biophysical characteristics of avian eggshells to cope with differential effects of solar radiation

Solar radiation is an important driver of animal coloration, not only because of the effects of coloration on body temperature but also because coloration may protect from the deleterious effects of UV radiation. Indeed, dark coloration may protect from UV, but may increase the risk of overheating. In addition, the effect of coloration on thermoregulation should change with egg size, as smaller eggs have higher surface‐volume ratios and greater convective coefficients than larger eggs, so that small eggs can dissipate heat quickly. We tested whether the reflectance of eggshells, egg spottiness, and egg size of the ground‐nesting Kentish plover Charadrius alexandrinus is affected by maximum ambient temperature and solar radiation at breeding sites. We measured reflectance, both in the UV and human visible spectrum, spottiness, and egg size in photographs from a museum collection of plover eggshells. Eggshells of lower reflectance (darker) were found at higher latitudes. However, in southern localities where solar radiation is very high, eggshells are also of dark coloration. Eggshell coloration had no significant relationship with ambient temperature. Spotiness was site‐specific. Small eggs tended to be light‐colored. Thermal constraints may drive the observed spatial variation in eggshell coloration, which may be lighter in lower latitudes to diminish the risk of overheating as a result of higher levels of solar radiation. However, in southern localities with very high levels of UV radiation, eggshells are of dark coloration likely to protect embryos from more intense UV radiation. Egg size exhibited variation in relation to coloration, likely through the effect of surface area‐to‐volume ratios on overheating and cooling rates of eggs. Therefore, differential effects of solar radiation on functions of coloration and size of eggshells may shape latitudinal variations in egg appearance in the Kentish plover.     

Carry‐over effects of multiple stressors on benthic embryos are mediated by larval exposure to elevated UVB and temperature

Damaging effects of UVB in conjunction with other stressors associated with global change are well‐established, with many studies focused on vulnerable early life stages and immediate effects (e.g., mortality, developmental abnormalities). However, for organisms with complex life cycles, experiences at one life stage can have carry‐over effects on later life stages, such that sublethal effects may mediate later vulnerability to further stress. Here, we exposed embryos in benthic egg masses of the New Zealand intertidal gastropod Siphonaria australis to treatments of either periodic stress (e.g., elevated UVB, salinity, and water temperature mimicking tidepool conditions in which egg masses are commonly found during summer) or control conditions (low UVB, ambient salinity, and water temperatures). Although there was high mortality from stressed egg masses, 24% of larvae hatched successfully. We then exposed the hatching larvae from both egg mass treatments to different combinations of water temperature (15 or 20 °C) and light (high UVB or shade) 12 h per day for 10 days. The most stressful larval conditions of 20 °C/high UVB resulted in low survival and stunted growth. Carry‐over effects on survival were apparent for shaded larvae exposed to elevated temperature, where those from stressed egg masses had 1.8× higher mortality than those from control egg masses. Shaded larvae were also larger and had longer velar cilia if they were from control egg masses, independent of larval temperature. These results demonstrate that previous experience of environmental stress can influence vulnerability of later life stages to further stress, and that focus on a single life stage will underestimate cumulative effects of agents of global change.     

The short- and long-term response of <Emphasis Type="Italic">Scrippsiella trochoidea</Emphasis> (Pyrrophyta) to solar ultraviolet radiation

To assess the short- and long-term impacts of UV radiation (UVR, 280–400 nm) on the microalga Scrippsiella trochoidea, we exposed cells to three different radiation treatments (PAB: 280–700 nm, PA: 320–700 nm, and P: 400–700 nm). A significant decrease in the photochemical efficiency (Φ_PSII) at high irradiance (100% of incident solar radiation, 216.0 W m⁻²) was observed. Photoinhibition was reduced from 62.7 to 10.9% when the cells were placed in 12% solar radiation (26.1 W m⁻²). In long-term experiments (11 days) using batch cultures, cell densities during the first 5 days were decreased under treaments P, PA, and PAB, reflecting a change in the irradiance experienced in the laboratory to that of incident solar irradiance. Thereafter, specific growth rates increased and UV-induced photoinhibition decreased, indicating acclimation to solar UV. Cells were found to exhibit both higher ratios of repair to UV-related damage, shorter period for recovery and increased concentrations of UV-absorbing compounds (UV_abc), whose maximum absorption was found to be at 336 nm. Our data indicate that S. trochoidea is sensitive to ultraviolet radiation, but was able to acclimate relatively rapidly (ca. 6 days) by synthesizing UV_abc and by increasing the rates of repair processes of D1 protein in PSII.     

UV-B susceptibility and photoreactivation in embryonic development of the two-spotted spider mite, <Emphasis Type="Italic">Tetranychus urticae</Emphasis>

Developmental errors are often induced in the embryos of many organisms by environmental stress. Ultraviolet-B radiation (UV-B) is one of the most serious environmental stressors in embryonic development. Here, we investigated susceptibility to UV-B (0.5 kJ m^?2) in embryos of the two-spotted spider mite, Tetranychus urticae, to examine the potential use of UV-B in control of this important agricultural pest worldwide. Peak susceptibility to UV-B (0% hatchability) was found in T. urticae eggs 36–48 h after oviposition at 25 °C, which coincides with the stages of morphogenesis forming the germ band and initial limb primordia. However, hatchability recovered to?~?80% when eggs irradiated with UV-B were subsequently exposed to visible radiation (VIS) at 10.2 kJ m^?2, driving photoreactivation (the photoenzymatic repair of DNA damage). The recovery effect decreased to 40–70% hatchability, depending on the embryonic developmental stage, when VIS irradiation was delayed for 4 h after the end of exposure to UV-B. Thus UV-B damage to T. urticae embryos is critical, particularly in the early stages of morphogenesis, and photoreactivation functions to mitigate UV-B damage, even in the susceptible stages, but immediate VIS irradiation is needed after exposure to UV-B. These findings suggest that nighttime irradiation with UV-B can effectively kill T. urticae eggs without subsequent photoreactivation and may be useful in the physical control of this species.     

Immobile and tough versus mobile and weak: effects of ultraviolet B radiation on eggs and larvae of Manduca sexta

Although indirect effects of solar ultraviolet (UV) radiation on insects are well known (e.g. UV radiation can modify plant chemistry), direct effects of solar radiation on insects have received little attention. Radiation in the UVB range (300–320 nm) is damaging because it is absorbed directly by proteins and DNA. UVB should be toughest on immobile or small life stages, such as eggs or early larval instars. In the present study, the effects of UVB radiation on eggs and larvae of the tobacco hornworm Manduca sexta L. (Lepidoptera: Sphingidae) are examined. The present study aimed to address: what natural levels of UV do they experience; how does UVB affect the performance of eggs; and how does it affect the performance of larvae? In addition, do M. sexta larvae use behaviour to avoid UVB exposure and, consequently, are they physiologically less robust to UVB? In these experiments, eggs and late larval instars of M. sexta are found to be robust to natural levels of UV radiation. By contrast, young larvae are not only more susceptible to damage from UVB, but also they use behavioural means to avoid it. The strategy of using behaviour may relax selection pressures on morphological and physiological mechanisms for preventing (or recovering from) damage by environmental UV radiation.     

Effects of solar ultraviolet radiation on photochemical efficiency of <Emphasis Type="Italic">Chaetoceros curvisetus</Emphasis> (Bacillariophyceae)

To assess the short- and long-term impacts of Ultraviolet radiation (UVR, 280–400 nm) on the red tide alga Chaetoceros curvisetus, we exposed cells to three different solar radiation treatments–PAB:280–700 nm, PA:320–700 nm, and P:400–700 nm under 20°C incubated temperature. Short-term exposures were investigated: the photochemical efficiency (Φ_PSII) versus irradiance curves under six levels of solar radiation by covering the incubators with a variable number of neutral density screens (the irradiance thus varied from 100 to 3%) lasting 1 h, and long-term exposures were designed to assess how the cells acclimate to solar radiation (the growth, UV_abc and ratio of repair to damage rates of D1 protein were detected). A significant decrease in the photochemical efficiency (Φ_PSII) at high irradiance (100% of incident solar radiation, 261.6 Wm⁻²) was observed in short-term exposure (1 h). UVR-induced photoinhibition was reduced to 7% in 3% solar radiation (4.08 Wm⁻²), compared with 66% in 100% solar radiation (261.6 Wm⁻²). In long-term experiments (11 days) using batch cultures, cell densities during the first 6 days were relatively constant for treatment P, and decreased slightly under PA and PAB treaments, reflecting a change in the irradiance experienced in the laboratory to that of incident solar irradiance. Thereafter, cell density increased and UV-induced photoinhibition decreased with the following days, indicating acclimation to solar UV. At the end of experiment, cells were found to exhibit both higher ratios of repair to UV-related damage and increased concentrations of UV-absorbing compounds, whose maximum absorption was found to be at 329 nm. Our data indicate that C. curvisetus is sensitive to ultraviolet radiation, but was able to acclimate relatively rapidly (ca. 6 days) by synthesizing UV-absorbing compounds and by increasing the rates of repair processes of D1 protein in PSII.     

Synergistic interactions within disturbed habitats between temperature, relative humidity and UVB radiation on egg survival in a diadromous fish

Anthropogenic impacts, including urbanization, deforestation, farming, and livestock grazing have altered riparian margins worldwide. One effect of changes to riparian vegetation is that the ground-level light, temperature, and humidity environment has also been altered. Galaxias maculatus, one of the most widely distributed fishes of the southern hemisphere, lays eggs almost exclusively beneath riparian vegetation in tidally influenced reaches of rivers. We hypothesized that the survival of these eggs is greatly affected by the micro-environment afforded by vegetation, particularly relating to temperature, humidity and UVB radiation. We experimentally reduced riparian vegetation height and altered shading characteristics, tracked egg survival, and used small ground-level temperature, humidity and UVB sensors to relate survival to ground-level effects around egg masses. The ground-level physical environment was markedly different from the surrounding ambient conditions. Tall dense riparian vegetation modified ambient conditions to produce a buffered temperature regime with constant high relative humidity, generally above 90%, and negligible UVB radiation at ground-level. Where vegetation height was reduced, frequent high temperatures, low humidity, and high UVB irradiances reduced egg survival by up to 95%. Temperature effects on egg survival were probably indirect, through reduced humidity, because developing eggs are known to survive in a wide range of temperatures. In this study, it was remarkable how such small variations in relatively small sites could have such a large effect on egg survival. It appears that modifications to riparian vegetation and the associated changes in the physical conditions of egg laying sites are major mechanisms affecting egg survival. The impacts associated with vegetational changes through human-induced disturbances are complex yet potentially devastating. These effects are particularly important because they affect a very small portion of habitat that is required to complete the life history of a species, despite the wide distribution of adults and juveniles across aquatic and marine environments.     

Influence of mid-ultraviolet (UVB) radiation on the physiology of the marine planktonic copepod Acartia omorii and the potential role of photoreactivation

The damaging effect of mid-ultraviolet (UVB, 280-320 nm) radiationon the marine planktonic copepod Acartia omorii was investigatedby using egg-hatching success, survival of various naupliarand copepodite stages, and feeding and egg production of adultfemales, as physiological parameters under different radiationconditions in the laboratory. No deleterious effect was inducedby UVA (320-400 nm) or PAR (400-700 nm), but UVB inflicted amore damaging effect with increasing UVB dose, Among variouslife stages, eggs, particularly freshly-spawned ones (< 2hold), were most susceptible₅₀= 2.76 kJ m^–2) and adultfemales least susceptible (LD₅₀= 22.0 kJ m^–2). The feedingand egg production of adult females were not significantly reduceduntil the UVB dose was elevated to 15.0 kJ m^–2. The UVB-induceddamage was alleviated under simultaneous irradiation with enhancedPAR. This photorepair mechanism was more effective for eggscompared with older stages. Our outdoor experiment using solarUVB demonstrated that present-day levels of solar UVB radiationcaused reduced hatching success of A. omorii eggs. In the habitatof A. omorii, however, due to high attenuation properties ofthe water, the solar UVB radiation may affect only young developmentalstages distributed near the sea surface.     

Ultraviolet light influences habitat preferences in a fish under predation risk

Environmental light conditions are of general importance in predator–prey interactions. In aquatic systems, prey individuals experience different levels of predation risk depending on the properties of the visual environment, such as structural complexity or water transparency. To reduce the threat of predation, prey should move to habitats providing better protection against visual predators. We studied the role of UV wavelengths in habitat choice behaviour under predation risk in a fish, the three-spined stickleback (Gasterosteus aculeatus) that uses UV signals in different contexts of intraspecific communication. In a laboratory experiment sticklebacks were exposed to a predatory threat and given the choice between two escape habitats, one providing full-spectrum conditions including UV light (UV+) and one without UV wavelengths (UV−). Fish from two rearing treatments were tested, one group had been raised under natural lighting conditions (UV+), the other group under UV-deficient lighting conditions (UV−). Sticklebacks from the UV+ group preferred the UV− habitat as a refuge which suggests that predator avoidance behaviour is UV-related in this species with UV− conditions presumably being advantageous for prey fish. However, individuals from the UV− treatment group were equally attracted to both presented light habitats. It is possible that these fish could not discriminate between the two light habitats due to physiological limitations caused by their rearing conditions. Further control trials with neutral-density filters revealed that the UV− habitat preference of UV+ fish in the main experiment was rather not influenced by a difference in achromatic brightness between the UV+ and UV− habitat.     

Seasonal patterns of egg production in field colonies of the termite <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> (Isoptera: Rhinotermitidae)

This is the first report on the annual egg production patterns in mature termite colonies in the field. Data on the seasonal patterns of egg production in field colonies are very important for understanding the annual colony growth schedule, resource allocation, and population dynamics of the termites. However, collecting the eggs from a sufficient number of colonies is extremely difficult in Reticulitermes termites because their multiple-site nesting makes it difficult to find the reproductive center of the colonies. Here, we first show the seasonal pattern of egg production in the subterranean termite Reticulitermes speratus by collecting the reproductive center of ten colonies each month from April through October. We had to destructively examine dozens of nests to find eggs from enough field colonies each month. Mature field colonies began to produce eggs in late May, soon after the swarming season, and the egg production rate (EPR) reached its maximum in early July. The eggs hatched until late October. The EPR was significantly correlated with the average monthly temperature. Additional investigation of the egg distributions in the nests showed that most eggs were kept around the royal cell, which contained the reproductives. The largest colony had 109 supplemental queens and 94,023 eggs, suggesting that each queen produced an average of 24.7 eggs per day, based on the known mean hatching period of an inseminated egg of 34.95±0.12 (SE) days.     

丁氟螨酯对二斑叶螨生长发育的影响

[目的]丁氟螨酯是一种新型酰基乙腈类非内吸性杀螨剂,对害螨的各个螨态都有很高活性,具有较高的应用价值.本文评价了丁氟螨酯对二斑叶螨生长发育的影响,以期为合理用药和二斑叶螨的综合防治提供理论依据.[方法]采用浸叶法测定丁氟螨酯对二斑叶螨成螨与卵的致死中浓度、雌成螨产卵量、各螨态存活率以及各发育历期的影响.[结果]经丁氟螨...     

Effects of UVB Radiation on the Initial Stages of Growth of Gigartina Skottsbergii, Sarcothalia Crispata and Mazzaella Laminarioides (Gigartinales, Rhodophyta)

The effects of UVB radiation on the growth of macroalgal thalli were evaluated using tetrasporophytic fronds of the Rhodophytes Gigartina skottsbergii, Sarcothalia crispata and Mazzaella laminarioides. The tetrasporophytic fronds were collected from nature and the tetrasporophyte sporelings grown in a temperature regulated chamber at 8 ± 2 ^∘C with a 12L:12D (Light: Dark) photoperiod, Photosynthetically Active Radiation (PAR) of 55 μmol photons m⁻² s⁻¹ and seawater enriched with 20 mL L⁻¹ of Provasoli medium. We exposed the thalli of these macroalgae to PAR (55 μmol photons m⁻² s⁻¹) and three treatments using a combination of PAR with three different levels of UVB radiation (0.10, 0.15 and 0.23 W m⁻² for G. skottsbergii and S. crispata and 0.02, 0.05 and 0.10 W m⁻² for M. laminarioides) during a period of 71 days. Growth of thalli was quantified by measuring their length using digitized photographs of samples.Important differences were detected in the growth of individuals cultured under the effects of UVB radiation, when compared to the control (i.e. plants exposed to PAR only). In the case of G. skottsbergii and S. crispata higher levels of UVB radiation resulted in slower growth of thalli. In nearly all measurements for the first two species, UVB radiation levels of 0.1 W m⁻² induced differences in thallus growth, while for M. laminarioides levels of UVB radiation of 0.1 W m⁻² were effective only after a prolonged period of exposure.Differential effects of UVB radiation on G. skottsbergii, S. crispata and M. laminarioides could interfere with the natural populations of these economically important macroalgal species in southern Chile, where they occur under the annual influence of the Antarctic Ozone Hole and the general thinning of the ozone layer.     

Drought tolerance in eggs and juveniles of the Iberian slug, <Emphasis Type="Italic">Arion lusitanicus</Emphasis>

The spread of invasive species is an increasing problem world wide. The invasive slug Arion lusitanicus has spread to most parts of Europe, where it often is considered as a serious pest. There is a need for better knowledge of its ecophysiology to be able to predict the effect of climatic factors, such as temperature and humidity on the population dynamics and abundance. The aim of the present study was to assemble data on the water balance and drought tolerance of eggs and juveniles of A. lusitanicus. Both eggs and juveniles had little capacity to prevent evaporative water loss and lost water when the ambient humidity fell below 99.8 and 99.5%, respectively. The water conductance of the cuticle of juveniles was 242 μg cm⁻² h⁻¹ mmHg⁻¹ and resembles that of other slug species. Both eggs and juveniles of A. lusitanicus tolerate a substantial water loss. There was no difference in water loss resistance between eggs and juveniles, but the eggs were slightly more tolerant to water loss than the juveniles. The percent water loss causing 50% mortality was 72% for the juveniles and 81% for the eggs. Despite A. lusitanicus’ tolerance of substantial water loss, its survival depends on humid habitats.     

Fumigant activity of essential oils and their components from Eucalyptus codonocarpa and E. dives against Tetranychus urticae (Acari: Tetranychidae) at three temperatures

Essential oils derived from eighteen species of the Myrtaceae family native to Australia, and major constituents of two oils selected from these oils were tested for their fumigant activity against adult females and eggs of Tetranychus urticae Koch (Acari: Tetranychidae) at 5, 15 and 25°C. Essential oils of Eucalyptus codonocarpa and Eucalyptus dives showed the highest fumigant activity against female adults at 10 μl/l at 15 and 25°C. Among major constituents of the two essential oils, piperitone was the most effective against female adults, followed by terpinene‐4‐ol at 10 μl/l at all three temperatures. The two essential oils and these two constituents lowered egg hatchability at 10 μl/l at 25°C. Our results suggest that piperitone should be further investigated as a potential fumigant against T. urticae.     

UV effects on photosynthesis and DNA in propagules of three Antarctic seaweeds (<Emphasis Type="Italic">Adenocystis utricularis</Emphasis>, <Emphasis Type="Italic">Monostroma hariotii</Emphasis> and <Emphasis Type="Italic">Porphyra endiviifolium</Emphasis>)

Ozone depletion is highest during spring and summer in Antarctica, coinciding with the seasonal reproduction of most macroalgae. Propagules are the life-stage of an alga most susceptible to environmental perturbations therefore, reproductive cells of three intertidal macroalgal species Adenocystis utricularis (Bory) Skottsberg, Monostroma hariotii Gain, and Porphyra endiviifolium (A and E Gepp) Chamberlain were exposed to photosynthetically active radiation (PAR), PAR + UV-A and PAR + UV-A + UV-B radiation in the laboratory. During 1, 2, 4, and 8 h of exposure and after 48 h of recovery, photosynthetic efficiency, and DNA damage were determined. Saturation irradiance of freshly released propagules varied between 33 and 83 μmol photons m⁻² s⁻¹ with lowest values in P. endiviifolium and highest values in M. hariotii. Exposure to 22 μmol photons m⁻² s⁻¹ PAR significantly reduced photosynthetic efficiency in P. endiviifolium and M. hariotii, but not in A. utricularis. UV radiation (UVR) further decreased the photosynthetic efficiency in all species but all propagules recovered completely after 48 h. DNA damage was minimal or not existing. Repeated exposure of A. utricularis spores to 4 h of UVR daily did not show any acclimation of photosynthesis to UVR but fully recovered after 20 h. UVR effects on photosynthesis are shown to be species-specific. Among the tested species, A. utricularis propagules were the most light adapted. Propagules obviously possess good repair and protective mechanisms. Our study indicates that the applied UV dose has no long-lasting negative effects on the propagules, a precondition for the ecological success of macroalgal species in the intertidal.     

UVB radiation and its role in the treatment of postmenopausal women with osteoporosis

 In humans, the serum concentration of parathyroid hormone (PTH) is higher in winter than in summer. The increase of PTH can be suppressed by oral vitamin D supplements, which is considered beneficial to those with osteoporosis. The present study investigates whether this effect can also be achieved by serial ultraviolet (UV) irradiation of the skin. In total, 34 women suffering from postmenopausal osteoporosis were included in the open trial. In late winter, 20 patients were irradiated with a spectrum containing UVB, eight times over a period of 4 weeks. The serum concentrations of 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)₂D], PTH, osteocalcin, alkaline phosphatase (AP), calcium and phosphorus were measured before the first, and 2 days after the last, dose of radiation. The data were compared to the controls (n=14, no UV exposure), who were evaluated once at the start of the study and then again 4 weeks later. After UV irradiation the level of 25(OH)D was increased, whilst that of PTH remained unchanged. The serum level of osteocalcin decreased in the control group, but did not change in the group of women who had been exposed to UV radiation. The present study of osteoporotic women does not confirm previous findings in studies of healthy volunteers i.e. that PTH can be suppressed by exposure to UVB radiation in winter. Further studies are required to specify whether there are subgroups of osteoporotic people who may benefit from exposure to UVB radiation during winter. Received: 31 October 1996 / Accepted: 21 October 1997