Photoprotective Compounds Research Articles

A Multitarget Approach toward the Development of 8-Substituted Purines for Photoprotection and Prevention of UV-Related Damage.

Ultraviolet (UV) light is the most abundant and significant modifiable risk factor for skin cancer and many other skin diseases such as early photo-aging. Across the solar radiation spectrum, UV light is the main cause behind skin problems. In the search for novel photoprotective compounds, a new series of 8-substituted purines were synthesized from commercially available 6-hydroxy-4,5-diaminopyrimidine hemisulfate or 4,5-diaminopyrimidine. All title compounds were investigated for their UV filtering, antioxidant, antifungal, and antiproliferative activities. For the photoprotection assays we used a diffuse transmittance technique to determine the sun protection factor (SPF) in vitro, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric ion reducing antioxidant power (FRAP) tests for evaluating the antioxidant activity of the more potent compounds. Among them, 8-(2,5-dihydroxyphenyl)-7H-purin-6-ol (compound 26) proved to be a good radical scavenger and is also endowed with broad-spectrum UVA filtering capabilities, suitable for further development as a protective molecule.

Screening and partial purification of photoprotective pigment scytonemin from cyanobacterial crusts dwelling on the historical monuments in and around Varanasi, India

In the present investigation, biological crusts from the surface of eight historical monuments of Varanasi, India, were examined for the presence of scytonemin (a cyanobacterial photoprotective pigment) containing cyanobacterial species. Lyngbya sp. and Scytonema sp. were the dominant cyanobacteria present in all crust samples. The absorption spectroscopic data of chlorophyll, carotenoids and scytonemin showed that scytonemin was more abundant than the carotene and chlorophyll in all the crusts. Identification of these compounds was done using UV-Vis spectroscopy and High Performance Liquid Chromatography (HPLC) analysis. HPLC analysis revealed the presence of scytonemin in seven out of eight samples and peaks of scytonemin with retention time ranging from 1.4-1.9 min with corresponding absorbance maxima at 386, 300 and 252±2 nm. As per our knowledge this is the first report of its kind from monuments of Varanasi. From this study, it can be concluded that synthesis of photoprotective compounds like scytonemin and its derivatives counteract the damaging effects of solar radiation which enable cyanobacteria to colonize and inhabit almost all kinds of habitats, including extreme lithic habitats, such as rocks and walls of monuments which face prolonged high intensity solar radiation.

Uncovering Potential Applications of Cyanobacteria and Algal Metabolites in Biology, Agriculture and Medicine: Current Status and Future Prospects.

Cyanobacteria and algae having complex photosynthetic systems can channelize absorbed solar energy into other forms of energy for production of food and metabolites. In addition, they are promising biocatalysts and can be used in the field of “white biotechnology” for enhancing the sustainable production of food, metabolites, and green energy sources such as biodiesel. In this review, an endeavor has been made to uncover the significance of various metabolites like phenolics, phytoene/terpenoids, phytols, sterols, free fatty acids, photoprotective compounds (MAAs, scytonemin, carotenoids, polysaccharides, halogenated compounds, etc.), phytohormones, cyanotoxins, biocides (algaecides, herbicides, and insecticides) etc. Apart from this, the importance of these metabolites as antibiotics, immunosuppressant, anticancer, antiviral, anti-inflammatory agent has also been discussed. Metabolites obtained from cyanobacteria and algae have several biotechnological, industrial, pharmaceutical, and cosmetic uses which have also been discussed in this review along with the emerging technology of their harvesting for enhancing the production of compounds like bioethanol, biofuel etc. at commercial level. In later sections, we have discussed genetically modified organisms and metabolite production from them. We have also briefly discussed the concept of bioprocessing highlighting the functioning of companies engaged in metabolites production as well as their cost effectiveness and challenges that are being addressed by these companies.

Mycosporine-Like Amino Acids (MAAs) Profile of Two Marine Red Macroalgae, Gelidium sp. and Ceramium sp.

Macroalgae have evolved different strategies to mitigate the damaging effects of solar ultraviolet radiation (UVR), including accumulation of photoprotective compounds such as mycosporine-like amino acids (MAAs). MAAs are secondary metabolites, synthesized by a large variety of organisms including macroalgae, phytoplanktons, cyanobacteria, lichen, fungi and some marine animals. MAAs act as photoprotectants and antioxidants. In the present investigation, MAAs profile of methanolic extracts of two marine red algae Gelidium sp. and Ceramium sp., collected from their natural environment, was studied. High-performance liquid chromatography (HPLC) and UV-Vis spectrometry analyses were used to reveal different MAAs profile in the extracts obtained from these two red algae. The MAAs isolated by HPLC were identified as shinorine (λmax= 333.5 nm), porphyra-334 (λmax=332.3 nm) and palythine (λmax=317.9 nm) having retention times (RT) 1.26, 2.12 and 3.64 min, respectively, in the extract obtained from Gelidium sp. Similarly, shinorine (λmax=332.3 nm), porphyra-334 (λmax=333.5 nm) and palythinol (λmax=332.5 nm) with RT 1.27, 2.13 and 4.61 min, respectively, were identified in the extract obtained from Ceramium sp. This study revealed that Gelidium sp. and Ceramium sp. could serve as potential source for economical exploration of MAAs in pharmaceutical sciences.Int. J. Appl. Sci. Biotechnol. Vol 5(1): 12-21

Distinct physiological and metabolic reprogramming by highbush blueberry (Vaccinium corymbosum) cultivars revealed during long-term UV-B radiation.

Despite the Montreal protocol and the eventual recovery of the ozone layer over Antarctica, there are still concerns about increased levels of ultraviolet-B (UV-B) radiation in the Southern Hemisphere. UV-B induces physiological, biochemical and morphological stress responses in plants, which are species-specific and different even for closely related cultivars. In woody plant species, understanding of long-term mechanisms to cope with UV-B-induced stress is limited. Therefore, a greenhouse UV-B daily course simulation was performed for 21 days with two blueberry cultivars (Legacy and Bluegold) under UV-BBE irradiance doses of 0, 0.07 and 0.19 W m-2 . Morphological changes, photosynthetic performance, antioxidants, lipid peroxidation and metabolic features were evaluated. We found that both cultivars behaved differently under UV-B exposure, with Legacy being a UV-B-resistant cultivar. Interestingly, Legacy used a combined strategy: initially, in the first week of exposure its photoprotective compounds increased, coping with the intake of UV-B radiation (avoidance strategy), and then, increasing its antioxidant capacity. These strategies proved to be UV-B radiation dose dependent. The avoidance strategy is triggered early under high UV-B radiation in Legacy. Moreover, the rapid metabolic reprogramming capacity of this cultivar, in contrast to Bluegold, seems to be the most relevant contribution to its UV-B stress-coping strategy.

Variación en la concentración de aminoácidos tipo micosporinas en macroalgas de las regiones de Valparaíso y Magallanes, Chile

The synthesis and accumulation of photoprotective compounds, as mycosporine-like amino acids (MAAs), is a mechanisms of protection against UV radiation. The photoprotective compounds synthesis can be induced under different stress factors, including intensity and spectral quality: PAR or UVR. The aim of this study was to assess the MAA concentration of 5 intertidal red seaweeds that inhabit the coast of Valparaiso. The results were compared with the MAAs concentration of the same species collected from Magellan Region in order to assess the latitudinal variation of these UV-absorbing compounds. The results indicate that MAA concentration changes with a latitudinal variation, being the species from Valparaiso (lower latitude and consequently, higher solar radiation) exhibited the higher photoprotective compound concentration.

Limestone dust alters the optical properties and traits of Fagus sylvatica leaves

Limestone dust altered spectral signatures of hypo-stomatal Fagus sylvatica leaves, mitigated the effect of high air temperatures, stimulated the production of chlorophylls, and reduced the amount of photo-protective compounds. Human activities and global changes to the environment result in increased concentrations of mineral dust in the atmosphere. This can have an impact on light harvesting in plants, and their energy balance and water management. The horizontally oriented, hypo-stomatal leaves of Fagus sylvatica present an efficient trap for dust particles. Two-year-old seedlings were treated for 3 weeks with two different concentrations of limestone dust from a quarry (median particle size 2 µm), and then, leaf optical properties and selected morphological, biochemical, and physiological traits were examined. Their adaxial and abaxial cuticle thickness and palisade/spongy parenchyma ratio were negatively correlated with dust concentration. For leaf biochemistry, chlorophyll levels were positively correlated with dust concentration, while the correlations of UV absorbing substances with dust concentration were negative. High-dust treatment positively affected the potential photochemical efficiency of photosystem II in the leaves, potentially due to lower leaf temperature. The reflectance spectra of the leaves following different dust treatments differed significantly along the visible and UV-A spectral regions, while they were most affected in the near infrared. The dust concentration explained 74 % (p = 0.001) of the variability of the reflectance spectra and only 20 % (p = 0.024) of the transmittance spectra. The present short-term study reveals that limestone dust can have positive effects on leaves with abaxial stomata, although the reduced photoprotection presents a risk of photoinhibition if the dust is removed by wind or water.

Are embryonic developing modes determinant in the acquisition and levels of photoprotective compounds in slipper limpets of the Crepipatella genus?

The type of embryonic development (mixed and direct) and its influence on the accumulation and translocation of photoprotective compounds from the mother to the encapsulated embryo was studied in the intertidal gastropods Crepipatella peruviana and Crepipatella dilatata during their reproductive peak. HPLC/MS was used to determine type and levels of sunscreen compounds (total carotenoids; TC/and mycosporine-like amino acid; MAA) in brooding females, capsule walls and early and pre-hatching embryos of both species. Photoprotective compounds were only quantified in nurse eggs of C. dilatata. Our results indicate that females of both species can accumulate TC and MAA at different levels, and they are able to transfer them selectively to capsule walls, embryos and nurse eggs. Palythine-serine (MW=244Da; λmax=320nm) and MAA-330 (MW=234Da; λmax=330nm) constitute total MAA pool in brooding females, whereas brooded embryos incorporate palythine (MW=244Da; λmax=320nm) to the MAA pool. Although TC was transferred from the mother to the embryo through the yolk in both species, MAA trespass showed differences. Females of C. peruviana transfer MAA to their embryos through the embryonic yolk; C. dilatata can transfer MAA only through their nurse eggs, which are consumed by embryos during the terminal stages of intracapsular development. Differences between mixed and direct embryonic development, as well as environmental UV-R levels, which the recently hatched larvae and juveniles of C. peruviana and C. dilatata are exposed to, would determine levels of sunscreen compounds in each species. Higher TC and MAA levels in pre-hatching larvae of C. peruviana compared to C. dilatata, indicate a necessity of C. peruviana for protection against UV-R radiation during approximately 15days when their veliger larvae remain in the water column before metamorphosis is complete. Conversely, low photoprotective levels in pre-hatching juveniles of C. dilatata could be related to low UV-R exposure levels due to the direct incorporation to the benthos and the presence of a protective shell.

Protection against UV-induced toxicity and lack of mutagenicity of Antarctic Sanionia uncinata.

Antarctica moss Sanionia uncinata (Hedw.) Loeske is exposed in situ to damaging levels of ultraviolet (UV) radiation. This moss has the ability to respond to UV radiation exposure producing secondary metabolites such as flavonoids, and has been recommended as a potential source of photoprotective compounds and antioxidants. The aim of the present paper was to investigate the free-radical scavenging activity and mutagenic and photomutagenic properties of methanolic (ME), hydroethanolic (HE) and ethanolic (EE) extracts of S. uncinata. The phenolic contents were evaluated by high-performance liquid chromatography (HPLC) and spectrophotometry. The findings showed that ME and EE presented the highest phenolic contents and inhibited free radical-scavenging activity against 2,2'-diphenyl-1 picrylhydrazyl (DPPH) and the HPLC analysis indicated several classes of phenolic acids and flavonoids. The sun protection factors (SPF) were determined by an in vitro method and the results showed significant values. The SPF values of BZ-3 at 50μg/mL increased significantly in association with ME, HE and EE. The extracts did not induce mutagenicity in auxotrophic Salmonella typhimurium histidine and photomutagenicity was not detected in the TA102 and TA104 strains after exposure to UV-A at doses of up to 6.5J/cm2 for the TA102 strain and up to 0.24J/cm2 for the TA104 strain. In addition, with the exception of ME, all the extracts induced photoprotective effects in the presence of the TA104 strain at 0.04J/cm2. The present results suggest that S. uncinata extracts did not induce photomutation and showed promise for photoprotection against the photobiological and ROS-inducing effects of the UV-A radiation.

Toxicity evaluation of the photoprotective compound LQFM048: Eye irritation, skin toxicity and genotoxic endpoints.

A new molecule, LQFM048, originally designed through molecular hybridization using green chemistry approach, is in development as a photoprotective agent. Eye irritation, skin toxicity and genotoxicity evaluations are mandatory for predicting health risks. In this context, the purpose of this study was to investigate the eye irritation potential of LQFM048 by combining Short Time Exposure (STE), Bovine Corneal Opacity and Permeability (BCOP) associated with corneal histomorphometry and Hen's Egg Test-Chorioallantoic Membrane (HET-CAM). Additionally, skin toxicity was evaluated by interleukin-18 production in the HaCaT keratinocyte, Local Lymph Node Assay (LLNA:BrdU-ELISA) method, 3T3 Neutral red uptake (NRU) assay and in vivo phototoxicity test. Genotoxic potential of LQFM048 was also analyzed by cytokinesis-block micronucleus assay (MNvit test-cytoB) in HepG2 cells. Our results showed that LQFM048 did not induce eye irritation and it was classified as UN GHS No Category for both STE and BCOP assays and non-irritating for HET-CAM test. LQFM048 showed non-potential skin sensitization with stimulation index (SI=0.7) in the LLNA:BrdU-ELISA method. Corroborating in vivo tests, it did not promote significant cytotoxicity in HaCaT cells and it showed similar levels of IL-18 when compared to control. Furthermore, LQFM048 induced non-phototoxic potential with photo-irritation factor (PIF) and mean photo effect (MPE) of 1 and -0.138, respectively, for 3T3 cells. Similarly, it was not phototoxic for in vivo testing with or without exposure to UVA, showing SI values of 1 and 1.2, respectively. The micronucleus test showed that LQFM048 was not genotoxic, under the conditions tested.In conclusion, LQFM048, a heterocyclic compound obtained through an environmentally acceptable simple synthetic route, seems to be safe for human use, especially for the development of a new sunscreen product, since it is neither an eye irritant, nor a contact allergen, nor mutagenic and nor phototoxic.

Photoprotective effect and acute oral systemic toxicity evaluation of the novel heterocyclic compound LQFM048

The new heterocyclic derivative LQFM048 (3) (2,4,6-tris ((E)-ethyl 2-cyano-3-(4-hydroxy-3-methoxyphenyl)acrylate)-1,3,5-triazine) was originally designed through the molecular hybridization strategy from Uvinul® T 150 (1) and (E)-ethyl 2-cyano-3-(4hydroxy-3-methoxyphenyl)acrylate (2) sunscreens, using green chemistry approach. This compound was obtained in global yields (80%) and showed an interesting redox potential. In addition, it is thermally stable up to temperatures around 250°C. It was observed that LQFM048 (3) showed a low degradation after 150min of sunlight exposure at 39°C, whereas the extreme radiation conditions induced a considerable photodegradation of the LQFM048 (3), especially when irradiated by VIS and VIS+UVA. During the determination of sun protection factor, LQFM048 (3) showed interesting results, specially as in association with other photoprotective compounds and commercial sunscreen. Additionally, the compound (3) did not promote cytotoxicity for 3T3 fibroblasts. Moreover, it was not able to trigger acute oral systemic toxicity in mice, being classified as a compound with low acute toxicity hazard (2.000mg/kg>LD50<5.000mg/kg). Therefore, this compound synthesized using green chemistry approach is promising showing potential to development of a new sunscreen product with advantage of presenting redox potential, indicating antioxidant properties.

Cold-Adapted Yeasts from Patagonia Argentina

The Patagonian Andes possess a great variety of glaciers, large temperate ice masses, and glacially formed water bodies. Most of these environments are included in protected areas characterized by low anthropogenic impact and minimal atmospheric pollution. Studies on occurrence of psychrotolerant (cold-adapted) and psychrophilic yeasts in these natural environments have allowed the characterization of native cold-adapted yeast communities, the description of six novel species, as well as description of the capability of these yeasts to produce extracellular enzymes, and other metabolites (carotenoids and mycosporines). Cold-adapted yeasts from Patagonian glaciers were able to hydrolyze natural polymers (casein, lipids, starch, pectin and carboxymethylcellulose) at low temperatures and some were able to produce photo-protective compounds. These results suggest a significant ecological role of these organisms as organic matter decomposers and nutrient cyclers, also reveal that some of these yeasts could be used for further metabolic, ecological and biotechnological studies. The objective of this review is to summarize all the findings related to cold adapted yeasts from glacial environments of the South Hemisphere (outside Antarctica), also to highlight the importance of continental ice masses from the microbiological perspective.&#x0D; Keywords: yeasts, psychrophilic, glaciers, extracellular enzymes.

Sensitivity and Acclimation of Three Canopy-Forming Seaweeds to UVB Radiation and Warming.

Canopy-forming seaweeds, as primary producers and foundation species, provide key ecological services. Their responses to multiple stressors associated with climate change could therefore have important knock-on effects on the functioning of coastal ecosystems. We examined interactive effects of UVB radiation and warming on juveniles of three habitat-forming subtidal seaweeds from Western Australia–Ecklonia radiata, Scytothalia dorycarpa and Sargassum sp. Fronds were incubated for 14 days at 16–30°C with or without UVB radiation and growth, health status, photosynthetic performance, and light absorbance measured. Furthermore, we used empirical models from the metabolic theory of ecology to evaluate the sensitivity of these important seaweeds to ocean warming. Results indicated that responses to UVB and warming were species specific, with Sargassum showing highest tolerance to a broad range of temperatures. Scytothalia was most sensitive to elevated temperature based on the reduced maximum quantum yields of PSII; however, Ecklonia was most sensitive, according to the comparison of activation energy calculated from Arrhenius’ model. UVB radiation caused reduction in the growth, physiological responses and thallus health in all three species. Our findings indicate that Scytothalia was capable of acclimating in response to UVB and increasing its light absorption efficiency in the UV bands, probably by up-regulating synthesis of photoprotective compounds. The other two species did not acclimate over the two weeks of exposure to UVB. Overall, UVB and warming would severely inhibit the growth and photosynthesis of these canopy-forming seaweeds and decrease their coverage. Differences in the sensitivity and acclimation of major seaweed species to temperature and UVB may alter the balance between species in future seaweed communities under climate change.

Seasonal Changes in Mycosporine-Like Amino Acid Production Rate with Respect to Natural Phytoplankton Species Composition.

After in situ incubation at the site for a year, phytoplanktons in surface water were exposed to natural light in temperate lakes (every month); thereafter, the net production rate of photoprotective compounds (mycosporine-like amino acids, MAAs) was calculated using 13C labeled tracer. This is the first report describing seasonal variation in the net production rate of individual MAAs in temperate lakes using a compound-specific stable isotope method. In the mid-latitude region of the Korean Peninsula, UV radiation (UVR) usually peaks from July to August. In Lake Paldang and Lake Cheongpyeong, diatoms dominated among the phytoplankton throughout the year. The relative abundance of Cyanophyceae (Anabaena spiroides) reached over 80% during July in Lake Cheongpyeong. Changes in phytoplankton abundance indicate that the phytoplankton community structure is influenced by seasonal changes in the net production rate and concentration of MAAs. Notably, particulate organic matter (POM) showed a remarkable change based on the UV intensity occurring during that period; this was because of the fact that cyanobacteria that are highly sensitive to UV irradiance dominated the community. POM cultured in Lake Paldang had the greatest shinorine (SH) production rate during October, i.e., 83.83 ± 10.47 fgC·L−1·h−1. The dominance of diatoms indicated that they had a long-term response to UVR. Evaluation of POM cultured in Lake Cheongpyeong revealed that there was an increase in the net MAA production in July (when UVR reached the maximum); a substantial amount of SH, i.e., 17.62 ± 18.34 fgC·L−1·h−1, was recorded during this period. Our results demonstrate that both the net production rate as well as the concentration of MAAs related to photoinduction depended on the phytoplankton community structure. In addition, seasonal changes in UVR also influenced the quantity and production of MAAs in phytoplanktons (especially Cyanophyceae).

Strategy of photo-protection in phytoplankton assemblages in the Kongsfjorden, Svalbard, Arctic

Photo-protective functions were investigated in phytoplankton assemblages at Kongsfjorden, Svalbard in spring, using their UV-absorbing compounds (mycosporine-like amino acids (MAAs)), xanthophyll pigments (diadinoxanthin (DD) and diatoxanthin (DT)) and - dimethylsulphoniopropionate ( -DMSP). The dominant phytoplankton species in the inner bay were dominated by Phaeocystis spp. and nanoflagellates, while the offshore waters were dominated by Thalassiosira spp. In the inner bay, UVabsorbing compounds and xanthophyll pigments exhibited higher ratios of MAA to chlorophyll a (MAA:chl a ratio), and both DD and DT to chlorophyll a (DD:chl a ratio and DT:chl a ratio), respectively. Thus, the photoprotective-pigments such as DD and DT appear to complement MAAs in the natural phytoplankton assemblage. However, the ratio of -DMSP to chlorophyll a ( -DMSP:chl a ratio) did not show a distinct spatial distribution according to environmental factors or interspecies differences. In this study, we found that photoprotective compounds occurred in a manner dependent on the phytoplankton species composition in Kongsfjorden Bay, where Phaeocystis is the dominant species.

Effect of Chronic Versus Pulse Perturbations on a Marine Ecosystem: Integration of Functional Responses Across Organization Levels

Human impacts accelerate the intensity and frequency of perturbations on ecosystems; approaches that integrate responses across organization levels are, however, lacking, particularly in the ocean. We experimentally simulated the frequency of fertilization (‘chronic’ versus ‘pulse’ events) in orthogonal combinations of two intensities (‘large’ versus ‘moderate’ fertilization) to determine physiological and biological responses by the seagrass Cymodocea nodosa and associated flora (epiphytes and green seaweeds, specifically Caulerpa prolifera), as well as functional changes (community primary and secondary productivity) at the ecosystem level. We predicted that the absence of recovery time from chronic perturbation would more severely affect responses at population and ecosystem levels relative to discrete events (pulses). Nutrient enrichment increased the biomass of C. prolifera irrespective of its frequency, whereas seagrass biomass and shoot density particularly decreased under a chronic scenario. These demographic responses were connected with varying photo-physiological performance of both C. nodosa and C. prolifera. Fertilization, regardless of its intensity and frequency, decreased the maximum photosynthetic rate of C. nodosa, concomitant with increased pigments, particularly under chronic fertilization, and decreased photoprotective (phenols) compounds. In contrast, fertilization boosted the maximum photochemical yield of C. prolifera, in addition to an increase in pigments and photoprotective compounds. Community primary and secondary productivity, however, did not vary under fertilization of varying intensity and frequency. In summary, fertilization precipitated population-level changes in physiological and biological attributes of vegetation. However, fertilization effects did not entirely cascade into ecosystem-level processes, that is, ecosystem productivity, which suggests a functional compensation (that is, increased algal performance to offset losses of seagrass production) during the initial stages of fertilization.

Evaluating the Photoprotective Effects of Ochre on Human Skin by In Vivo SPF Assessment: Implications for Human Evolution, Adaptation and Dispersal.

Archaeological indicators of cognitively modern behaviour become increasingly prevalent during the African Middle Stone Age (MSA). Although the exploitation of ochre is viewed as a key feature of the emergence of modern human behaviour, the uses to which ochre and ochre-based mixtures were put remain ambiguous. Here we present the results of an experimental study exploring the efficacy of ochre as a topical photoprotective compound. This is achieved through the in vivo calculation of the sun protection factor (SPF) values of ochre samples obtained from Ovahimba women (Kunene Region, Northern Namibia) and the Palaeozoic Bokkeveld Group deposits of the Cape Supergroup (Western Cape Province, South Africa). We employ visible spectroscopy, energy-dispersive X-ray fluorescence (ED-XRF), X-ray diffraction (XRD) and granulometric analyses to characterise ochre samples. The capacity of ochre to inhibit the susceptibility of humans to the harmful effects of exposure to ultraviolet radiation (UVR) is confirmed and the mechanisms implicated in the efficacy of ochre as a sunscreen identified. It is posited that the habitual application of ochre may have represented a crucial innovation for MSA humans by limiting the adverse effects of ultraviolet exposure. This may have facilitated the colonisation of geographic regions largely unfavourable to the constitutive skin colour of newly arriving populations.

Diel vertical migration, size distribution and photoprotection in zooplankton as response to UV‐A radiation

AbstractThe transparency regulator hypothesis (TRH) proposes that ultraviolet radiation (UVR) is a main driving force behind diel vertical migration (DVM) of zooplankton in clearwater systems. While previous studies have mainly studied DVM in relation to the TRH on a spatial scale across systems we here focus on long‐term trends in a single system in order to assess if UVR explains observed patterns in DVM. We show that the strength of DVM in Daphnia is to a large extent explained by UVR and we demonstrate a tipping point at which the UVR intensity drastically affects the strength of DVM in Daphnia. In contrast, the strength of DVM could not be explained by the level of UVR among calanoid copepods. The amount of photoprotective compounds did not differ between zooplankton found at different depths indicating that zooplankton do not change their vertical position in relation to the amount of accumulated photoprotective compounds. In addition, we show that both Daphnia and calanoid copepods display patterns of size structured migration.

The relationship between UV-irradiance, photoprotective compounds and DNA damage in two intertidal invertebrates with contrasting mobility characteristics

The photoprotective role of mycosporine-like amino acids (MAA) against the generation of DNA cyclobutane pyrimidine dimers (CPD) was studied in the sessile intertidal anemone Actinia tenebrosa and the mobile intertidal gastropod Diloma aethiops through 27months at a mid-latitude New Zealand location. MAA were sequestered by A. tenebrosa and D. aethiops from their diet, although maximum total MAA levels in both species were not correlated with seasonal variation in maximum ambient UV-B levels recorded at the collection site. Temporal changes in total MAA in A. tenebrosa showed a six months lag-time in their concentration regarding to the environmental UV-B levels. This lag period corresponded to an observed increase in CPD production from spring to summer; suggesting that MAA do not completely protect the anemone from UV-B during summer. For D. aethiops, total MAA concentrations did not change significantly during the study, although qualitative changes in MAA were apparent. A month lag-time in MAA concentration in D. aethiops and possibly the physical barrier that the shell confers to the animal, can explain reduced CPD levels in comparative terms with A. tenebrosa. Although MAA are used by invertebrates for photoprotection, contrasting mobility characteristics and the presence of physical adaptations can confer them important protection levels during temporal changes of UV-B at mid-latitude places of the Southern Hemisphere.

Anatomical, physiological and chemical differences between populations of Pseudocyphellaria flavicans (Hook. f. &amp; Taylor) Vain. from Chile

Environmental conditions can affect lichen morphology, physiology and chemistry. Some functional traits; like thickness of thalluslayers, photosystems condition, and presence of photoprotective and antioxidant compounds are key to colonizing new sites, and canchange depending on light and moisture availability. In the present study, we compared the morphology, physiology and chemistry ofthe native Chilean lichen Pseudocyphellaria flavicans from two Coastal populations (Nahuelbuta and Contulmo, Araucania district),and one Andean population (Ralco, Bio-Bio district). Ralco is a more closed secondary forest, and can show dryer periods comparedto Nahuelbuta and Contulmo. We found differences in thalli anatomy between populations. Ralco individuals had thinner uppercortex than Nahuelbuta individuals. Contulmo individuals had similar upper cortex thickness compared to the other two populations.We also found differences in the response of the maximal efficiency of the PSII (Fv/Fm) to desiccation and in the in situ valuesmeasured. We did not find differences between populations in the chemical traits. The differences between populations could beattributed to differences in local environmental conditions, namely moisture and light.