Optimal Light Conditions Research Articles

Attractive Effects of American Serpentine Leafminer, Liriomyza trifolii (Burgess), to Light-Emitting Diodes

Phototactic responses of Liriomyza trifolii adults to six different light-emitting diodes (LEDs) were investigated, and their responses were compared to that using a luring lamp (BLB) under laboratory conditions. Based on the attraction rate under optimal light conditions, the green LED (520 ± 5 nm) showed the highest attraction rate (99.7 %), followed by the yellow LED (590 ± 5 nm, 96.1 %), the red LED (625 ± 10 nm, 91.4 %), the blue LED (470 ± 10 nm, 91.2 %), the UV LED (365 nm, 71.0 %), and the IR LED (730 nm, 5.6 %). Moreover, the green LED was approximately 1.4 times more attractive than BLB (71.1 %) to L. trifolii adults. These results suggest that the green LED was the most useful for monitoring of L. trifolii adults under optimal conditions.

Early Growth and Physiological Characteristics of Parasenecio firmus by Shading Conditions in Forest Farming

Parasenecio firmus is a perennial plant in Asteraceae, Parasenecio that distributed in Korea, China, and Japan. As dietary style changes for well-being life, consumer demand for functional wild vegetable is increasing. P. firmus has great fragrance and texture and contains caffeoylquinic acid. It has the potential to be further developed as a functional wild vegetable. However, as the natural habitat of P. firmus is quite limited and it should be collected manually in natural stand. So it is need to be a scientific research for artificial cultivation in forest. This study was conducted to investigate the optimum light conditions of P. firmus in forest farming. In this experiment, P. firmus was grown under four different light conditions (50%, 30%, 20%, and 10% of full sunlight) and non-treated (full sunlight). Out of five different shading conditions, P. firmus has shown the best physiological and growth responses to 10% and 20% of full sunlight. There is no statistically significant difference in other shading conditions. At 10% of full sunlight, P. firmus has shown the highest level of statistical significance in the length of shoot, fresh weight of shoot, water contents in all part, SLA (specific leaf area) and LAR (leaf area ratio). It indicates higher water content level, thinner leaf, and wider light-interception areas. On the other hand, at 20% of full sunlight, root color diameter, root length, total fresh weight, total dry weight, leaf area, and chlorophyll contents turned out to be high. It shows that P. firmus is active in chlorophyll activities and carbon dioxide assimilation at even lower light conditions. These results suggest that the optimum light level of P. firmus for artificial cultivation ranges from 10 to 20% of full sunlight. These results can be used as basic data for forest farming.

Effect of stand edge on the natural regeneration of spruce, beech and Douglas-fir

Our work aimed at studying the strategy of woody plants regeneration during the regeneration of a spruce stand with the admixture of beech and Douglas-fir by border cutting (NW-SE aspect) on acidic sites of higher elevations in the Bohemian-Moravian Upland. Spruce is better adapted to bear shade than Douglas-fir. Nevertheless, in optimal light conditions up to a distance of ca. 35 m (about 16% DIFFSF) from the stand edge, the Douglas-fir can put the spruce into danger as to height growth. By contrast to beech, the density of spruce is significantly higher within the distance of 45 m (about 15% DIFFSF) from the stand edge but further on the situation would change to the benefit of beech. The density of Douglas-fir significantly dominates over beech within a distance of 35 m from the stand edge; from 55 m (less than 15% DIFFSF), the situation changes in favour of beech. Beech can survive in full shade deep in the stand core waiting for its opportunity to come. As compared to spruce and Douglas-fir, the height growth of beech was at all times significantly greater at a distance of 25 m from the stand edge. Converted to practical conditions, spruce and Douglas-fir with individually admixed beech seedlings showed good prosperity approximately up to a distance of one stand height from the edge. A mixture of spruce and beech did well at a greater distance but good prosperity at a distance of 2–3 stand heights was shown only by beech. Thus, border regeneration eliminates disadvantages of the climatic extremes of clear-cutting and specifics of shelterwood felling during which one – usually shade-tolerant tree species dominates in the natural regeneration (e.g. beech).

Mixed-color Illumination and Quick Optimum Search for Machine Vision

Quick search for optimal illumination using mixed color is proposed, and the possibility for use in industrial vision systems is considered. Multidimensional formulation of the optimum search methods is reviewed to use multiple inputs for various color sources and one output of image sharpness. The voltage inputs are used to adjust the intensity of each color source and the optimal illumination is found by the maximum of the sharpness. The optimum search methods reveal that the number of iterations for the optimal condition in mixed color illumination was under 0.1% the number required by equal section search. The searching paths and convergence were considered in both of the input coordinate and the color coordinate. The results show that the optimum search methods make it possible to find the optimal lighting conditions quickly and accurately.

A novel wastewater treatment and biomass cultivation system combining photosynthetic bacteria and membrane bioreactor technology

A new system combining photosynthetic bacteria (PSB) treatment with membrane bioreactor (MBR) separation, PSB-MBR, was constructed in this work to treat wastewater and cultivate biomass. PSB were used to remove pollutants and membrane was used to separate biomass from the effluent. The optimal light and oxygen condition for PSB treatment section was natural light–micro aerobic, and the optimal ratio of food to microbe (F/M) was 2.0. The optimal membrane operation pressure and flow rate for membrane separation was 0.1/0.2MPa and 27.5L/h, respectively. Under the optimal conditions, COD removal reached 99.3% and the biomass recovery efficiency was 99.5%. The backwash cycle of PSB-MBR system lasted for 48h, while the backwash cycle for conventional MBR systems is usually 0.5–3.0h. The prolonged backwash interval means simple operation, little backwash water consumption, and long service life of membrane. That could be caused by the low extracellular polymeric substance contain of PSB (9–11mg/g-VSS).

Phototactic behavior: Repellent effects of cigarette beetle, Lasioderma serricorne (Coleoptera: Anobiidae), to light-emitting diodes

Repellent effects of specific light wavelengths against the cigarette beetle were evaluated in blue (470 nm), green (520 nm), yellow (590 nm), and red (625 nm) light-emitting diodes (LEDs). Under optimal light conditions (100 lx luminance intensity, 2 h light exposure time), the blue LED (59%) was the most repellent to Lasioderma serricorne adults, followed by green (34.3%), yellow (31.3%), and red (29.3%) LEDs. Moreover, the blue LED was approximately 1.3 times more repellent to L. serricorne adults than a luring lamp black light (BL), 45.7%. These results suggest that blue LEDs could be used for environmentally friendly insect control.

First Record of the Harmful Raphidophyte <i>Chattonella marina</i> Bloom in Rushan Coast, China in 2008 after the Occurrence of the Green Tide

The red tide of Chattonella marina (Subrahmanyan) Hara & Chihara occurred in Rushan coast, Shandong Peninsula, China, in August 2008. Based on the four cruises of routine monitoring and four cruises of monitoring of the red tide in Rushan, the process of the red tide and possible mechanism were analyzed. During the bloom, the maximum area of the red tide was about 100 km2; the maximum average cell abundance of C. marina reached 1.46×106 cells/L; surface water temper-ature ranged between 26.1 °C and 27.2 °C, and salinity between 26.6 ‰ and 30.3 ‰. The material released from the decayed green tide species Ulva prolifera could provide a chance for the bloom of C. marina, combined the optimum sea temperature, light and nutrient condition. It was the first time to link a red tide event with the consequence of the green tide in Yellow Sea, which could give an attention on our future monitoring and management.

Entrainment of Circadian Rhythms to Environmental cycles in Lactuca sativa L. - Characteristics of Circadian Rhythms in Lettuce -

The circadian clock that exists in terrestrial organisms to trigger various physiological phenomena within a period of approximately 24 hours. This approximate time range of 24 hr periodicity is called the “circadian rhythm”. Recently, the studies of circadian rhythms suggest that the control of circadian rhythm can contribute to improvement of the productivity of plant growth (called circadian resonance). Therefore, it is necessary to investigate the features of circadian rhythm and to search for optimal light conditions that best suit plant cultivation. In this study, we analyzed the characterization of circadian rhythms through a luciferase luminescence assay in Lactuca sativa L.

High-light vs. low-light: Effect of light acclimation on photosystem II composition and organization in Arabidopsis thaliana

The structural response of photosystem II (PSII) and its light-harvesting proteins (LHCII) in Arabidopis thaliana after long-term acclimation to either high or low light intensity was characterized. Biochemical and structural analysis of isolated thylakoid membranes by electron microscopy indicates a distinctly different response at the level of PSII and LHCII upon plant acclimation. In high light acclimated plants, the C2S2M2 supercomplex, which is the dominating form of PSII in Arabidopsis, is a major target of structural re-arrangement due to the down-regulation of Lhcb3 and Lhcb6 antenna proteins. The PSII ability to form semi-crystalline arrays in the grana membrane is strongly reduced compared to plants grown under optimal light conditions. This is due to the structural heterogeneity of PSII supercomplexes rather than to the action of PsbS protein as its level was unexpectedly reduced in high light acclimated plants. In low light acclimated plants, the architecture of the C2S2M2 supercomplex and its ability to form semi-crystalline arrays remained unaffected but the density of PSII in grana membranes is reduced due to the synthesis of additional LHCII proteins. However, the C2S2M2 supercomplexes in semi-crystalline arrays are more densely packed, which can be important for efficient energy transfer between PSII under light limiting conditions.

The Biological Characteristics and its Sequence Analysis of <i>Pholiota adiposa</i>

In this paper, the biological characteristics of Pholiota adiposa were systematically studied. The results showed that the ideal temperature range for growth is from 20 °C to 25°C, with optimal temperature at 25°C; the optimal light condition is full darkness; the ideal pH range for growth is from 5 to 9, with optimal pH at 6; the preferred carbon source is sucrose, followed by glucose; the preferred nitrogen source is potassium nitrate, glutamic acid. The internal transcribed spacer region (ITS) was sequenced to determine whether the DNA sequence data supported the experimental result. The phylogenetic tree for the 19 pieces of homologous sequences were analyzed, with the highest homology reaching 99%.

Microbial Iron(II) Oxidation in Littoral Freshwater Lake Sediment: The Potential for Competition between Phototrophic vs. Nitrate-Reducing Iron(II)-Oxidizers

The distribution of neutrophilic microbial iron oxidation is mainly determined by local gradients of oxygen, light, nitrate and ferrous iron. In the anoxic top part of littoral freshwater lake sediment, nitrate-reducing and phototrophic Fe(II)-oxidizers compete for the same e− donor; reduced iron. It is not yet understood how these microbes co-exist in the sediment and what role they play in the Fe cycle. We show that both metabolic types of anaerobic Fe(II)-oxidizing microorganisms are present in the same sediment layer directly beneath the oxic-anoxic sediment interface. The photoferrotrophic most probable number counted 3.4·105 cells·g−1 and the autotrophic and mixotrophic nitrate-reducing Fe(II)-oxidizers totaled 1.8·104 and 4.5·104 cells·g−1 dry weight sediment, respectively. To distinguish between the two microbial Fe(II) oxidation processes and assess their individual contribution to the sedimentary Fe cycle, littoral lake sediment was incubated in microcosm experiments. Nitrate-reducing Fe(II)-oxidizing bacteria exhibited a higher maximum Fe(II) oxidation rate per cell, in both pure cultures and microcosms, than photoferrotrophs. In microcosms, photoferrotrophs instantly started oxidizing Fe(II), whilst nitrate-reducing Fe(II)-oxidizers showed a significant lag-phase during which they probably use organics as e− donor before initiating Fe(II) oxidation. This suggests that they will be outcompeted by phototrophic Fe(II)-oxidizers during optimal light conditions; as phototrophs deplete Fe(II) before nitrate-reducing Fe(II)-oxidizers start Fe(II) oxidation. Thus, the co-existence of the two anaerobic Fe(II)-oxidizers may be possible due to a niche space separation in time by the day-night cycle, where nitrate-reducing Fe(II)-oxidizers oxidize Fe(II) during darkness and phototrophs play a dominant role in Fe(II) oxidation during daylight. Furthermore, metabolic flexibility of Fe(II)-oxidizing microbes may play a paramount role in the conservation of the sedimentary Fe cycle.

Influence of light intensity on the toxicity of atrazine to the submerged freshwater aquatic macrophyte Elodea canadensis

Light intensity can have a profound influence on the degree of phytotoxicity experienced by plants exposed to photosystem II (PSII) inhibiting herbicides. This relationship was evaluated in the submerged aquatic macrophyte Elodea canadensis exposed to three different concentrations of atrazine (510, 1000 and 2000μga.i./L) plus an untreated control at three different light intensities (0, 500 and 6000lx) under static-renewal conditions for 14 days. Under 500lx light intensity, control plants demonstrated a rapid increase in shoot length but minimal increase in dry shoot weight, suggesting limited photosynthesis. Based on shoot-length and biomass, growth was not affected by any atrazine exposure relative to controls under dark conditions (0lx). Under low-light conditions at 500lx, exposures to 510, 1000 and 2000μga.i./L atrazine significantly decreased net shoot lengths by 34%, 38% and 35%, respectively, relative to corresponding (500lx) controls. However, atrazine exposure under this light condition did not significantly decrease biomass (dry shoot weight). Compared to 6000lx, only approximately 8% of photosynthetically active radiation (PAR) was measured under 500lx intensity, indicating that minimal PAR was available for photosynthesis. Under optimal light conditions (6000lx), net shoot lengths significantly decreased in the treated atrazine groups by 48%, 51% and 68%, and net dry shoot weights (biomass) were significantly decreased by 79%, 81% and 91%, respectively, relative to corresponding (6000lx) controls. These data show that under low light conditions, atrazine-induced effects on dry shoot weight (biomass) are dependent on available PAR and active photosynthesis.

Modeling Filamentous Cyanobacteria Reveals the Advantages of Long and Fast Trichomes for Optimizing Light Exposure

Cyanobacteria form a very large and diverse phylum of prokaryotes that perform oxygenic photosynthesis. Many species of cyanobacteria live colonially in long trichomes of hundreds to thousands of cells. Of the filamentous species, many are also motile, gliding along their long axis, and display photomovement, by which a trichome modulates its gliding according to the incident light. The latter has been found to play an important role in guiding the trichomes to optimal lighting conditions, which can either inhibit the cells if the incident light is too weak, or damage the cells if too strong. We have developed a computational model for gliding filamentous photophobic cyanobacteria that allows us to perform simulations on the scale of a Petri dish using over 105 individual trichomes. Using the model, we quantify the effectiveness of one commonly observed photomovement strategy—photophobic responses—in distributing large populations of trichomes optimally over a light field. The model predicts that the typical observed length and gliding speeds of filamentous cyanobacteria are optimal for the photophobic strategy. Therefore, our results suggest that not just photomovement but also the trichome shape itself improves the ability of the cyanobacteria to optimize their light exposure.

Growth and photosynthetic characteristics of blueberry ( Vaccinium corymbosum cv. Bluecrop) under various shade levels

Blueberry can readily be shaded as a bush type plant, maybe affecting its growth and photosynthesis. Growth and photosynthetic characteristics of ‘Bluecrop’ blueberry grown under various shade levels were investigated to understand acclimation under shade conditions and to determine the optimal light conditions for agricultural purpose. Shade decreased the number of shoots per shrub, but increased shoot length. However, shade did not affect the number of leaves on the main axis. With increasing shade level, leaf length, width and area increased, but leaf thickness decreased. However, there was no obvious tendency in leaf length/width ratio with increasing shade level. Shade leaves had less dense stomata than sun leaves, but stoma was bigger in shade leaves than in sun leaves. With increasing shade level, non-photochemical quenching in blueberry leaves increased and the values were higher at low photosynthetic photon flux densities (PPFDs) in shade leaves than in sun leaves, resulting in the decreases in quantum yield, electron transport rate and net CO 2 assimilation rate ( A n). The maximum A n at 31, 60, 73 and 83% shade levels was 11.8, 11.0, 8.4 and 7.5 μmol m −2 s −1, respectively. Following the slight decrease up to 100 μmol m −2 s −1 PPFD, stomatal conductance ( g s) linearly increased up to 600 μmol m −2 s −1 PPFD and became saturated at all shade levels. The leaves of the shrubs grown under the 83% shade level had a significantly lower g s as compared to the leaves of the shrubs grown under the 31, 60 and 73% shade levels. Transpiration rate ( E) linearly increased up to 600 μmol m −2 s −1 PPFD and was saturated at the 73 and 83% shade levels. However, E increased linearly at both 31 and 60% shade levels with increasing PPFD. The reproductive growth characteristics such as number of flowers, fruit set rate per flower bud and fruit yield also significantly decreased with increasing shade level. For agricultural purpose, therefore, shade level above approximately 60% of full sunlight must be avoided for optimal photosynthesis and growth of the ‘Bluecrop’ blueberry.

The Research on Effect of Ambient Light on the Impact of the Soft Proofing

Soft proofing technology is the development of new technologies in recent years, application is becoming more widely. As the use of display image simulating hard copy image, display settings, ambient light conditions and the observe conditions will affect the impact of soft proofing. 68 pairs of test images own the average value of different color originated from four typical images by transfer functions. In the image manipulation progress, each original image was altered in two aspects: lightness, chroma respectively .Using EIZO CG19 display to show in different ambient light conditions. A visual evaluation experiment was carried out aiming at test images by a psychophysical experiment, testing and analyzing color difference resolution influence of display image under different ambient light conditions, optimal lighting conditions and ranges of the soft proofing viewing environment was determined.

Online Analysis of Coal on A Conveyor Belt by use of Machine Vision and Kernel Methods

The application of machine vision systems to measure particle size distributions has among other things been driven by sophisticated control systems used to monitor and control mills and other ore-processing systems. Machine vision is nonintrusive and offers reliable online measurements in potentially harsh environments. Although considerable advances have been made over the last decade, reliability of measurements with segmentation algorithms is still an issue, particularly where lighting conditions may vary, fines are present, or heterogeneous particle surfaces may result in irregular reflection of light. In practice the alternative to online measurement of particle size distributions is sieve analysis, which is slow and tedious and not suitable for control purposes. The efficient preparation and quality control of coal are important for stable and effective operation of the Sasol® FBDB™ Gasification Process. The operation of these gasifiers depend among other on melting properties and composition of the ash, thermal and mechanical fragmentation, and caking properties of the coal, as well as the particle size distribution of the coal. Although many of these properties can be assessed in some way to expedite process improvement, particle size distributions are difficult to estimate beforehand from feedstocks, since these distributions may change significantly during the feeding process, or by insufficient screening, resulting in an access/increase of fine coal to gasification. The ability to measure these distributions online would therefore play a crucial role in continuous process improvement and real-time quality control. The objective of this project is to explore the use of image analysis to quantify the amount of fines (<6 mm) present for different coal samples under conditions simulating the coal on conveyor belts similar to those being used by Sasol for gasification purposes. Quantification of the fines will be deemed particularly successful, if the fines mass fraction, as determined by sieve analysis, is possible to be predicted with an error of less than 10%. In this article, kernel-based methods to estimate particle size ranges on a pilot-scale conveyor belt as well as edge detection algorithms are considered. Preliminary results have shown that the fines fraction in the coal on the conveyor belt could be estimated with a median error of approximately 24.1%. This analysis was based on a relatively small number of sieve samples (18 in total) and needs to be validated by more samples. More samples would also facilitate better calibration and may lead to improved estimates of the sieve fines fractions. Similarly, better results may also be possible by using different approaches to image acquisition and analysis, but discussion of these falls outside the scope of the present article. Most of the error in the fines estimates can be attributed to sampling and to fines that were randomly obscured by the top layer (of larger particles) of coal on the belt. Sampling errors occurred as a result of some breakage of the coal between the sieve analyses and the acquisition of the images. The percentage of the fines obscured by the top layer of the coal probably caused most of the variation in the estimated mass of fines, but this needs to be validated experimentally. Preliminary studies have indicated that some variation in the lighting conditions have a small influence on the reliability of the estimates of the coal fines fractions and that consistent lighting conditions are more important than optimal lighting conditions.

Protein oxidative changes in whole and skim milk after ultraviolet or fluorescent light exposure

We investigated how protein changes occur, at the primary or higher structural levels, when proteins are exposed to UV or fluorescent (FL) light while in the complex matrix, milk. Whole milk (WM) or skim milk (SM) samples were exposed to FL or UV light from 0 to 24h at 4°C. Protein oxidation was evaluated by the formation of protein carbonyls (PC), dityrosine bond (DiTyr), and changes in molecular weight (protein fragmentation and polymerization). Oxidative changes in AA residues were measured by PC. Dityrosine and N′-formylkynurenine (NFK), a carbonylation derivative of Trp, were measured by fluorometry. Protein carbonyls increased as a function of irradiation time for both WM and SM. The initial rate for PC formation by exposure to FL light (0.25 or 0.27nmol/h for WM and SM, respectively) was slower than that following exposure to UV light (1.95 or 1.20 nmol/h, respectively). The time course of NFK formation resembled that of PC. After 24h of UV exposure, SM had significantly higher levels of NFK than did WM. In contrast, WM samples irradiated with UV had higher levels of DiTyr than did SM samples, indicating different molecular pathways. The formation of intra- or intermolecular DiTyr bonds could be indicative of changes in the tertiary structure or oligomerization of proteins. The existence of NFK suggests the occurrence of protein fragmentation. Thus, proteolysis and oligomerization were analyzed by sodium dodecyl sulfate-PAGE. After 24h of exposing WM to UV or FL light, all the proteins were affected by both types of light, as evidenced by loss of material in most of the bands. Aggregates were produced only by UV irradiation. Hydrolysis by pepsin and enzyme-induced coagulation by rennet were performed to evaluate altered biological properties of the oxidized proteins. No effect on pepsin digestion or rennet coagulation was found in irradiated SM or WM. The oxidative status of proteins in milk and dairy products is of interest to the dairy industry and consumers. These findings provide knowledge that could be useful in determining the optimal lighting conditions in the dairy industry in general and in cheese making in particular.

Spectral attenuation of solar radiation in Patagonian fjord and coastal waters and implications for algal photobiology

The spectral attenuation of solar irradiation was measured during summer in two types of coastal waters in southern Chile, a north Patagonian fjord (Seno Reloncaví) and open coast (Valdivia). In order to relate the light availability with the light requirements of upper subtidal seaweeds, the saturating irradiance for photosynthesis ( E k) from P– I curves was measured. In addition the UV risk was assessed. Based on the z 1% of PAR, the lower limit of the euphotic zone in the studied systems averaged 21 m ( K d 0.24 m −1) in Seno Reloncaví and 18 m ( K d 0.27 m −1) in the coast of Valdivia. Photosynthesis of the studied seaweeds was saturated at markedly lower irradiances than found in their natural depths at the time of the study. Solar radiation penetrating into these depths at both locations largely supports the light requirements for the photosynthesis of subtidal species: 50–160 μmol m −2 s −1 for seaweeds from Seno Reloncaví (7 m tidal range) and 20–115 μmol m −2 s −1 for Valdivia assemblages (2 m tidal range). Optimal light conditions to saturate photosynthesis ( E k) were present at 10–16 m water depth. The attenuation of solar irradiation did not vary significantly between the fjord and coastal sites of this study. However, the underwater light climates to which seaweeds are exposed in these sites vary significantly because of the stronger influence of tidal range affecting the fjord system as compared with the open coastal site. The patterns of UV-B penetration in these water bodies suggest that seaweeds living in upper littoral zones such as the intertidal and shallow subtidal (<3 m) may be at risk.

Moonstruck primates: owl monkeys (Aotus) need moonlight for nocturnal activity in their natural environment.

Primates show activity patterns ranging from nocturnality to diurnality, with a few species showing activity both during day and night. Among anthropoids (monkeys, apes and humans), nocturnality is only present in the Central and South American owl monkey genus Aotus. Unlike other tropical Aotus species, the Azara's owl monkeys (A. azarai) of the subtropics have switched their activity pattern from strict nocturnality to one that also includes regular diurnal activity. Harsher climate, food availability, and the lack of predators or diurnal competitors, have all been proposed as factors favoring evolutionary switches in primate activity patterns. However, the observational nature of most field studies has limited an understanding of the mechanisms responsible for this switch in activity patterns. The goal of our study was to evaluate the hypothesis that masking, namely the stimulatory and/or inhibitory/disinhibitory effects of environmental factors on synchronized circadian locomotor activity, is a key determinant of the unusual activity pattern of Azara's owl monkeys. We use continuous long-term (6–18 months) 5-min-binned activity records obtained with actimeter collars fitted to wild owl monkeys (n = 10 individuals) to show that this different pattern results from strong masking of activity by the inhibiting and enhancing effects of ambient luminance and temperature. Conclusive evidence for the direct masking effect of light is provided by data showing that locomotor activity was almost completely inhibited when moonlight was shadowed during three lunar eclipses. Temperature also negatively masked locomotor activity, and this masking was manifested even under optimal light conditions. Our results highlight the importance of the masking of circadian rhythmicity as a determinant of nocturnality in wild owl monkeys and suggest that the stimulatory effects of dim light in nocturnal primates may have been selected as an adaptive response to moonlight. Furthermore, our data indicate that changes in sensitivity to specific environmental stimuli may have been an essential key for evolutionary switches between diurnal and nocturnal habits in primates.

Occurrence of a Cylindrospermopsis bloom in Louisiana

Cylindrospermopsis raciborskii occurs predominantly in tropical to subtropical freshwaters but appears to be spreading to temperate regions. After the hurricanes of 2005, a bloom of this organism took place in Lake Dauterive and Lake Fausse Pointe in Louisiana. The cyanobacterium dominated the phytoplankton community for three months. Of the three known morphotypes (straight, coiled and spiral) only coiled and spiral were found. In June 2006, 60% of the organisms were of the spiral morphotype but the relative abundance of this morphotype decreased dramatically within the month of June. However, the average density for both morphotypes remained the same until September. Densities (up to 160,000 cells/mL) significantly exceeded the threshold for toxicity. Because the sampled region offers optimal light and nutrient conditions, it is likely that C. raciborskii has been established in this region and future blooms can be expected. Therefore, a monitoring program should be implemented.