Does sun glare increase antipredator behaviour in prey?

As the sun gradually lowers over the horizon, prey species with more sun in their eyes should have more difficulty in visually monitoring their surroundings for threats and thus experience a higher predation risk. In a unique setting, I could examine changes in antipredator behaviour in a prey species, the semipalmated sandpiper Calidris pusilla, facing attacks by peregrine falcons Falco peregrinus, which originated from the general direction of the lowering sun. I predicted gradual changes in antipredator behaviour as sun glare becomes more problematic later in the day. As the day progressed, sandpipers occurred in sparser groups when the sun glared but not when clouds obscured the sun, suggesting that fewer individuals engaged in risky foraging. Pecking rate and foraging success decreased later in the day when the sun glared but not otherwise implying an increase in vigilance at the expense of foraging. When more sun hit their eyes, sandpipers also moved faster suggesting increased skittishness. The sun glare effect might be relevant to any species foraging in open areas not only when the sun sets but also when it rises especially if predators can target prey species at these vulnerable times. The temporal gradient in predation risk that the sun glare effect creates might thus apply broadly and have important consequences for antipredator vigilance, foraging efficiency, and habitat use.     

Black and white under the South African sun: are juvenile Cape gannets heat stressed?

(1) We measured dorsal surface temperature (T_d), skin temperature (T_s) and body temperature (T_b) of adult (white plumage) and juvenile (black plumage) Cape gannets, Morus capensis, subject to high ambient temperatures. (2) Mean T_d and T_b of juveniles were significantly elevated compared to those of adults. (3) Mean T_s of older juveniles, which had down beneath their body feathers, were significantly lower than T_s of younger juveniles, indicating that the down provided insulation. (4) Juveniles spent a significantly greater proportion of time thermoregulating via evaporative cooling than adults. (5) The high thermal load of the dark plumage is presumably associated with major costs for the thermal and water balance of juveniles.     

Life in the land of the midnight sun: are northern lizards adapted to longer days?

The relative importance of genetic and environmental factors for explaining differences in trait distributions between populations is one of the major issues in evolutionary biology. In ectotherms, temperature can have a major impact on morphology, physiology, and life history strategies, and has often been inferred to explain differences between populations. In species with active thermoregulation, however, the ambient temperature may not be as important as the opportunity for thermoregulation. We studied growth in juvenile common lizards ( Lacerta vivipara ) originating from two environments differing in such thermal opportunity (i.e. day length). The populations differed significantly in their norms of reaction, with lizards experiencing long days in the wild showing a steeper increase in growth rate with increasing thermal opportunity. The environment with longer days also has a lower mean temperature in the wild, and in accordance with evolutionary predictions, lizards from this population had higher endurance at low temperatures. Both populations showed genetic variation in degree of phenotypic plasticity in growth rate as evident from the extensive crossing in norms of reaction.     

Cutaneous photobiology. The melanocyte vs. the sun: who will win the final round?

Solar ultraviolet radiation (UV) is a major environmental factor that dramatically alters the homeostasis of the skin as an organ by affecting the survival, proliferation and differentiation of various cutaneous cell types. The effects of UV on the skin include direct damage to DNA, apoptosis, growth arrest, and stimulation of melanogenesis. Long-term effects of UV include photoaging and photocarcinogenesis. Epidermal melanocytes synthesize two main types of melanin: eumelanin and pheomelanin. Melanin, particularly eumelanin, represents the major photoprotective mechanism in the skin. Melanin limits the extent of UV penetration through the epidermal layers, and scavenges reactive oxygen radicals that may lead to oxidative DNA damage. The extent of UV-induced DNA damage and the incidence of skin cancer are inversely correlated with total melanin content of the skin. Given the importance of the melanocyte in guarding against the adverse effects of UV and the fact that the melanocyte has a low self-renewal capacity, it is critical to maintain its survival and genomic integrity in order to prevent malignant transformation to melanoma, the most fatal form of skin cancer. Melanocyte transformation to melanoma involves the activation of certain oncogenes and the inactivation of specific tumor suppressor genes. This review summarizes the current state of knowledge about the role of melanin and the melanocyte in photoprotection, the responses of melanocytes to UV, the signaling pathways that mediate the biological effects of UV on melanocytes, and the most common genetic alterations that lead to melanoma.     

Is the bark of shining gum (Eucalyptus nitens) a sun or a shade leaf?

Photoinhibition and pigment composition of green stem tissues of field-grown adult Eucalyptus nitens were measured on clear spring days with low morning temperatures—conditions that cause photoinhibition in leaves of many plant species. The sun-exposed (north-facing) bark contained less chlorophyll a+b (531 vs 748 mol m^–2), neoxanthin (29 vs 41), and -carotene (54 vs 73), more xanthophyll cycle pigments per unit surface area and per unit chlorophyll (71 vs 53 mol m^–2 and 141 vs 66 mmol mol^–1 chlorophyll), and less lutein per unit chlorophyll (239 vs 190) than the shaded (southern) side. Maximum electron flow rates were 60 mol m^–2 s^–1 on the sun-exposed side, and about 10 mol m^–2 s^–1 on the shaded side. F_v/F_m was always lower than 0.8 on the sun-exposed side and the de-epoxidation state (DEPS) of the xanthophyll cycle was dominated by zeaxanthin in midday samples. F_v/F_m increased quickly after darkening, but DEPS recovered more slowly to 40% overnight. This suggested that rapidly reversible pH-dependent quenching was responsible for the bulk of changes in PS II efficiency. F_v/F_m remained below 0.8 overnight, which may well be indicative of photo-damage to PSII. In contrast, DEPS of the shaded side was lower, and F_v/F_m was higher, than for the sun-exposed side. We conclude that E. nitens chlorenchyma on the sun-exposed stem side has a photosynthetic pigment composition similar to sun leaves and it experiences significant photoinhibition in the field.     

Risk attitudes and sun protection behaviour: Can behaviour be altered by using a melanoma genomic risk intervention?

Background: Exposure to ultraviolet radiation from sunlight is directly associated with melanoma skin cancer, however reducing sun-exposure can be difficult to achieve at a population level.Methods: Using a genomic risk information behaviour change trial for melanoma prevention, we classified participants as risk-seeking, risk-neutral or risk-averse for domain-specific risk taking (DOSPERT). One-way ANOVA determined the association between socio-demographic characteristics and risk-taking score, and multivariable linear regression ascertained impact of an individual’s underlying risk propensity on an objective measure of sun-exposure, standard erythemal dose (SED), at 3-months follow-up.Results: Of 119 participants, mean age 53 years; 50% males, 87% had a personal/family history of cancer; 19% were classified risk-seeking, 57% risk-neutral. The mean risk-taking score was significantly higher in younger participants (≤50 years: 13.86 vs. >50 years: 11.11, p = 0.003); and lower in those with a personal/family history of skin cancer versus without (10.55 vs 13.33, p = 0.009). Risk averse individuals had lower weekly mean SEDs at 3-months than risk neutral and risk seeking individuals (2.56, 5.81, 4.81 respectively, p = 0.01). Risk seekers showed fewer sun protective habits (p < 0.001); and higher intentional tanning, (p = 0.01). At 3-months, risk seekers attained 16%–54% lower SEDs in the genomic information group compared with controls, however this was not significantly different across risk groups (interaction p = 0.13).Conclusion: An individual’s underlying risk attitude is likely associated with sun-exposure behaviours, and may modify the effect of a genomic risk information behaviour change intervention. Young people and risk seekers may benefit most from being given information on their genetic risk of melanoma.     

From ecophysiology to phenomics: some implications of photoprotection and shade–sun acclimation in situ for dynamics of thylakoids in vitro

Half a century of research into the physiology and biochemistry of sun–shade acclimation in diverse plants has provided reality checks for contemporary understanding of thylakoid membrane dynamics. This paper reviews recent insights into photosynthetic efficiency and photoprotection from studies of two xanthophyll cycles in old shade leaves from the inner canopy of the tropical trees Inga sapindoides and Persea americana (avocado). It then presents new physiological data from avocado on the time frames of the slow coordinated photosynthetic development of sink leaves in sunlight and on the slow renovation of photosynthetic properties in old leaves during sun to shade and shade to sun acclimation. In so doing, it grapples with issues in vivo that seem relevant to our increasingly sophisticated understanding of ΔpH-dependent, xanthophyll-pigment-stabilized non-photochemical quenching in the antenna of PSII in thylakoid membranes in vitro.     

Impacts of El Niño related drought and forest fires on sun bear fruit resources in lowland dipterocarp forest of East Borneo

Droughts and forest fires, induced by the El Niño/Southern Oscillation (ENSO) event, have increased considerably over the last decades affecting millions of hectares of rainforest. We investigated the effects of the 1997–1998 forest fires and drought, associated with an exceptionally severe ENSO event, on fruit species important in the diet of Malayan sun bears (Helarctos malayanus) in lowland dipterocarp forest, East Kalimantan, Indonesian Borneo. Densities of sun bear fruit trees (≥10 cm DBH) were reduced by ～80%, from 167±41 (SD) fruit trees ha^?1 in unburned forest to 37±18 fruit trees ha^?1 in burned forest. Densities of hemi-epiphytic figs, one of the main fallback resources for sun bears during periods of food scarcity, declined by 95% in burned forest. Species diversity of sun bear food trees decreased by 44% in burned forest. Drought also affected sun bear fruit trees in unburned primary forest, with elevated mortality rates for the duration of 2 years, returning to levels reported as normal in region in the third year after the ENSO event. Mortality in unburned forest near the burn-edge was higher (25±5% of trees ≥10 cm DBH dead) than in the forest interior (14±5% of trees), indicating possible edge effects. Combined effects of fire and drought in burned primary forest resulted in an overall tree mortality of 78±11% (≥10 cm DBH) 33 months after the fire event. Disturbance due to fires has resulted in a serious decline of fruit resources for sun bears and, due to the scale of fire damage, in a serious decline of prime sun bear habitat. Recovery of sun bear populations in these burned-over forests will depend on regeneration of the forest, its future species composition, and efforts to prevent subsequent fire events.     

Considering the potential benefits as well as adverse effects of sun exposure: can all the potential benefits be provided by oral vitamin D supplementation?

Exposure to ultraviolet radiation (UVR) is associated with both adverse and beneficial health effects. While many of the adverse effects of excessive exposure are well known, the adverse effects of insufficient UVR exposure are less clear-cut, but may include a heightened risk of several cancers and autoimmune disorders as well as of bone diseases such as rickets, osteomalacia and osteoporosis. Although some of the postulated beneficial effects of UVR exposure may occur through the maintenance of adequate levels of vitamin D, it is not clear that this can account for all of these effects. We briefly review the epidemiological literature with respect to vitamin D, UVR exposure and autoimmune diseases. We further outline alternative pathways, whereby UVR could alter the risk of development of some cancers and autoimmune disorders, independent of effects on vitamin D synthesis. Recognition of the beneficial effects of UVR exposure has led to a reconsideration of sun avoidance policies. It is important to recognize that all of the beneficial effects of UVR exposure may not occur only through UVR-induced vitamin D synthesis. Thus maintaining current sun avoidance policies while supplementing food with vitamin D may not be sufficient to avoid the risks of insufficient exposure to UVR.     

The use of webcam images to determine tourist–climate aptitude: favourable weather types for sun and beach tourism on the Alicante coast (Spain)

Climate has an obvious influence on tourism as a resource and as a location factor for tourist activities. Consequently, the tourist phenomenon in general is heavily controlled by meteorological conditions—in short, by the climate. In this article, the author proposes a set of weather types with which to establish the climate aptitude for sun and beach tourism. To determine these types, the density of use of one of the beaches with the lowest seasonality in continental Europe, the Levante Beach in Benidorm (Alicante, Spain), was analysed. Beach attendance was monitored using a webcam installed by the “Agencia Valenciana de Turismo”. The relationship between the density of use of the lower and upper beach areas on the one hand, and meteorological variables on the other, allowed comfort (physiological equivalent temperature) and enjoyment (fractions of solar radiation) thresholds to be established. The appropriate hydric comfort values were obtained by comparing the ranges proposed by Besancenot in 1989 [Besancenot (1989) Clima et turismes. Massom, París] with numbers of visitors to the beach. The wind velocity and precipitation thresholds were selected following consultation with the literature and considering the climatic characteristics of the environment under analysis. Based on a combination of these thresholds, weather types suitable for this specific tourist activity are defined. Thus, this article presents a method for assessing the extent to which a day on the beach can be enjoyed. This has a number of applications, for planners, the tourism business and consumers alike. The use of this (filter) method in climate databases and meteorological forecasts could help determine the tourist season, the suitability of setting up a business associated with sun and beach tourism, as well as help plan holidays and program a day’s leisure activities. Thus, the article seeks to improve our understanding of the climate preferences of that tourist activity par excellence: sun and beach tourism.     

Melanocortin 1 receptor (MC1R), pigmentary characteristics and sun exposure: Findings from a case–control study of diffuse large B-cell and follicular lymphoma

The relationship between skin cancer and non-Hodgkin lymphoma (NHL) suggests common genetic, host or environmental causes. Ultraviolet radiation (UVR), pigmentary characteristics have been linked with both malignancies, and for skin cancer, the melanocortin 1 receptor (MC1R) which influences pigmentation has also been implicated. This paper reports on the relationship between MC1R, skin, hair and eye colour, time spent outdoors, and diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). Persons carrying MC1R homozygote variant alleles at R151C, R160W, D294H and D84E were more likely to have fair skin, red hair and to spend less time outdoors than those who did not. The variant allele at V92M was associated with FL (odds ratio (OR) = 1.61, 95% confidence interval (CI) 1.08–2.39) and the r:wild type genotype with DLBCL (OR = 0.58, 95% CI 0.38–0.89). Interactions between MC1R genotypes and skin colour influenced DLBCL risk; the RR genotype increased risk in individuals with medium or dark skin, based on 5 cases and no controls, but decreased risk among those of fair skin. On the whole, DLBCL and FL risk were not related to genetic variation in MC1R, pigmentation or time spent outdoors.