Expertomica Fishgui: comparison of fish skin colour

The colour hue and saturation of the fish skin are important factors in fish breeding, reflecting the momentary physiological status of the fish. Algorithms evaluating fish colour were created in the MATLAB environment and compiled in the stand‐alone application, Expertomica Fishgui. Fish groups fed on several diets (varying in carotenoid supplements) were compared as concerns image analysis methods on colour changes. Images were processed and evaluated to locate body positions, areas and colour saturation. Conversion from the Red‐Green‐Blue (RGB) colour space to chromatic colours was carried out to reduce the colour space. The threshold of skin chromatic colour was set on basis of the chromatic histograms using Otsu automatic bimodal segmentation. The average colour was calculated through all pixels of the selected area in the original image and through all images of the group. Colour conversion to the Hue‐Saturation‐Value (HSV) colour space was also carried out. Relative deviation between the saturation of samples in the control and the experimental groups provided a means of judgement. The dominant wavelength was also determined.     

Genetics of seed-coat colour in Citrullus lanatus (Thunb.) Mansf.

Summary Intervarietal crosses in watermelon, Citrullus lanatus (Thunb.) Mansf., involving six parents with black (J18-1 and J 75), brown (J56-1 and N.H. Midget), red (Bykovski-199) or light cream (Red Nectar) seed-coat colour were made. Parents, F₁, F₂ and backcross populations were evaluated for their phenotypic expressions with regard to the seed-coat colours involved. Black colour was monogenically dominant over brown light cream and red colour of seed-coat separately or independently. Red colour was dominant over light cream colour of seed-coat by a single pair of genes. The light cream colour was recessive to the brown seed-coat colour of watermelon where a single pair of genes was involved.     

Learning of colour and position cues in domestic chicks: Males are better at position,females at colour

Male and female chicks were trained to discriminate between two boxes for food reinforcement. The correct box was indicated by a colour cue (red or brown) and a position cue (right or left). After learning, the colour and the position cues were dissociated: the right-left location of the two boxes was alternated between trials according to a semi-random sequence.The chicks were thus retrained to discriminate either on the basis of colour (irrespective of position) or on the basis of position (irrespective of colour). There were no sex differences, during training, with both position and colour cues. However, during re-training females performed better on the colour learning task and males performed better on the position learning task.     

Genetic parameters of coat colour in golden fox (Vulpes vulpes L.)

Genetic parameters (heritability, genetic and phenotypic correlations) of chosen coat colour traits of golden fox were estimated. 1013 animals, born on the Sniaty fox farm (Poland) in 1985-1999 were evaluated. In 1993-1999 colour type was additionally assessed for 833 animals, by detailed evaluation of coat colour on the back and sides of the body, throat colour, belly colour and the amount of silver hair. The REML method was used to estimate genetic (co)variance components. Data were transformed using the probit transformation. Heritability estimates for coat traits were low (0.04 to 0.22). Values of most of the estimated genetic parameters (h2, rG, rP) were comparable to those frequently reported for other colour types of silver fox.     

Comparative psychophysics of bumblebee and honeybee colour discrimination and object detection

Bumblebee (Bombus terrestris) discrimination of targets with broadband reflectance spectra was tested using simultaneous viewing conditions, enabling an accurate determination of the perceptual limit of colour discrimination excluding confounds from memory coding (experiment 1). The level of colour discrimination in bumblebees, and honeybees (Apis mellifera) (based upon previous observations), exceeds predictions of models considering receptor noise in the honeybee. Bumblebee and honeybee photoreceptors are similar in spectral shape and spacing, but bumblebees exhibit significantly poorer colour discrimination in behavioural tests, suggesting possible differences in spatial or temporal signal processing. Detection of stimuli in a Y-maze was evaluated for bumblebees (experiment 2) and honeybees (experiment 3). Honeybees detected stimuli containing both green-receptor-contrast and colour contrast at a visual angle of approximately 5 degrees , whilst stimuli that contained only colour contrast were only detected at a visual angle of 15 degrees . Bumblebees were able to detect these stimuli at a visual angle of 2.3 degrees and 2.7 degrees , respectively. A comparison of the experiments suggests a tradeoff between colour discrimination and colour detection in these two species, limited by the need to pool colour signals to overcome receptor noise. We discuss the colour processing differences and possible adaptations to specific ecological habitats.     

Colour removal from landfill leachate by coagulation and flocculation processes

A study was conducted to investigate the efficiency of coagulation and flocculation processes for removing colour from a semi-aerobic landfill leachate from one of the landfill sites in Malaysia. Four types of coagulant namely aluminium (III) sulphate (alum), ferric (III) chloride, ferrous (II) sulphate and ferric (III) sulphate were studied using standard jar test apparatus. Results indicated that ferric chloride was superior to the other coagulants and removed 94% of colour at an optimum dose of 800 mg/l at pH 4. The effect of coagulant dosages on colour removal showed similar trend as for COD, turbidity and suspended solids. This suggested that colour in landfill leachate was mainly contributed by organic matters with some insoluble forms that exhibited turbidity and suspended solids readings. The results from this study suggested that ferric chloride could be a viable coagulant in managing colour problems associated with landfill leachate.     

Reproducibility of electronic tooth colour measurements

Clinical methods of investigation, such as tooth colour determination, should be simple, quick and reproducible. The determination of tooth colours usually relies upon manual comparison of a patient's tooth colour with a colour ring. After some days, however, measurement results frequently lack unequivocal reproducibility. This study aimed to examine an electronic method for reliable colour measurement. The colours of the teeth 14 to 24 were determined by three different examiners in 10 subjects using the colour measuring device Shade Inspector. In total, 12 measurements per tooth were taken. Two measurement time points were scheduled to be taken, namely at study onset (T(1)) and after 6 months (T(2)). At either time point, two measurement series per subject were taken by the different examiners at 2-week intervals. The inter-examiner and intra-examiner agreement of the measurement results was assessed. The concordance for lightness and colour intensity (saturation) was represented by the intra-class correlation coefficient. The categorical variable colour shade (hue) was assessed using the kappa statistic. The study results show that tooth colour can be measured independently of the examiner. Good agreement was found between the examiners.     

Degradation of predigested distillery effluent by isolated bacterial strains

Batch studies were conducted on degradation of anaerobically digested distillery wastewater by three bacterial strains, viz. Xanthomonas fragariae, Bacillus megaterium and Bacillus cereus in free and immobilized form, isolated from the activated sludge of a distillery wastewater treatment plant. The removal of COD and colour with all the three strains increased with time up to 48 hr and only marginal increase in COD and colour removal efficiency was observed beyond this period up to 72 hr. After this period removal efficiency remained fairly constant up to 120 hr. The maximum COD and colour removal efficiency varied from 66 to 81% and 65 to 75%, respectively for both free and immobilized cells of all the three strains. The strain Bacillus cereus showed the maximum efficiency of COD (81%) and colour (75%) removal out of the three strains. An interrelationship between the percent COD and colour removal was carried out by correlation and regression analysis and was justified by high values of coefficient of correlation (r = 0.99) for all the cases. The first order removal rate kinetics was also applied and rate constants were evaluated for COD and colour removal efficiencies.     

The effect of accelerated ageing on colour stability of visible light-cured (VLC) chairside denture liners

doi: 10.1111/j.1741‐2358.2011.00458.x
The effect of accelerated ageing on colour stability of visible light–cured (VLC) chairside denture liners Objective: The purpose of this study was to assess the colour stability of seven visible light–cured (VLC) hard and soft denture liners by an in vitro accelerated ageing test and compare them with two autopolymerised hard and soft liners. Materials and methods: Ten specimens of each material were fabricated. The initial colour was measured with a tri‐stimulus colorimeter. One set of five specimens was placed in distilled water at 37°C in the dark for 15 days, while the remaining were subjected to UV/visible light‐accelerated ageing initially for 24 h and then for 144 h. Colour change (ΔΕ) was calculated. Data were statistically analysed by anova , Tukey and t‐tests at α = 0.05. Results: All the liners showed clinically acceptable colour change (ΔΕ ≤ 6.8) in distilled water. The colour changes after ageing for Triad DuaLine, Lightdon U, Ufi Gel H and Light Liner Hard were clinically unacceptable (ΔΕ ≥ 6.8), whereas LightLiner Soft, Astron LC Soft, Triad Resiline and Flexacryl Soft presented slighter and clinically acceptable colour change (ΔΕ ≤ 6.8). Conclusion: Accelerated ageing affected significantly the colour stability of all denture liners tested except Astron LC Soft. Soft VLC denture liners were more colour‐stable than hard VLC liners.     

Greenish blue flower colour of Strongylodon macrobotrys

The flower colour of Strongyledon macrobotrys is luminous blue green and attracts bats for pollination. The chemical basis for development of the flower colour was investigated. The flower contained an anthocyanin (malvin) and a flavone (saponarin), approximately 1:9 (malvin: saponarin) in molar ratio. The pH of the pigmented epidermal cell sap of the jade vine petal was exceptionally high, 7.90, while the pH value of the colourless inner tissue was 5.60. Copigmentation test using the mixtures of malvin and saponarin (1:9 M ratio) at various pH values revealed that the characteristic blue green colour of the jade vine is developed by copigmentation of malvin with saponarin in slightly alkaline cell sap, pH 7.9. In the copigmentation in slightly alkaline condition, saponarin shows a strong yellow colour, which gives a greenish tone to the flower colour.     

Rapid evolution of elaborate male coloration is driven by visual system in Australian fairy‐wrens (Maluridae)

The interplay between colour vision and animal signalling is of keen interest to behavioural ecologists and evolutionary biologists alike, but is difficult to address in terrestrial animals. Unlike most avian lineages, in which colour vision is relatively invariant among species, the fairy‐wrens and allies (Maluridae) show a recent gain of ultraviolet sensitivity (UVS). Here, we compare the rates of colour evolution on 11 patches for males and females across Maluridae in the context of their visual system. We measured reflectance spectra for 24 species, estimating five vision‐independent colour metrics as well as metrics of colour contrast among patches and sexual dichromatism in a receiver‐neutral colour space. We fit Brownian motion (BM) and Ornstein–Uhlenbeck (OU) models to estimate evolutionary rates for these metrics and to test whether male coloration, female coloration or dichromatism was driven by selective regimes defined by visual system or geography. We found that in general male coloration evolved rapidly in comparison with females. Male colour contrast was strongly correlated with visual system and expanded greatly in UVS lineages, whereas female coloration was weakly associated with geography (Australia vs. Papua New Guinea). These results suggest that dichromatism has evolved in Maluridae as males and females evolve at different rates, and are driven by different selection pressures.     

Effect of redox mediator, AQDS, on the decolourisation of a reactive azo dye containing triazine group in a thermophilic anaerobic EGSB reactor

The feasibility of thermophilic (55 °C) anaerobic treatment applied to colour removal of a triazine contained reactive azo dye was investigated in two 0.53 l expanded granular sludge blanket (EGSB) reactors in parallel at a hydraulic retention time (HRT) of 10 h. Generally, this group of azo dyes shows the lowest decolourisation rates during mesophilic anaerobic treatment. The impact of the redox mediator addition on colour removal rates was also evaluated. Reactive Red 2 (RR2) and anthraquinone-2,6-disulfonate (AQDS) were selected as model compounds for azo dye and redox mediator, respectively. The reactors achieved excellent colour removal efficiencies with a high stability, even when high loading rates of RR2 were applied (2.7 g RR2 l⁻¹ per day). Although AQDS addition at catalytic concentrations improved the decolourisation rates, the impact of AQDS on colour removal was less apparent than expected. Results show that the AQDS-free reactor R2 achieved excellent colour removal rates with efficiencies around 91%, compared with the efficiencies around 95% for the AQDS-supplied reactor R1. Batch experiments confirmed that the decolourisation rates were co-substrate dependent, in which the volatile fatty acids (VFA) mixture was the least efficient co-substrate. The highest decolourisation rate was achieved in the presence of either hydrogen or formate, although the presence of glucose had a significant impact on the colour removal rates.     

Disentangling the selective factors that act on male colour in wild guppies

The colour pattern of male guppies ( Poecilia reticulata ) is thought to evolve as a compromise between sexual selection (favouring conspicuousness) and natural selection (favouring crypsis). Underpinning this classic explanation is the observation that guppies living with dangerous fish predators are less colourful than guppies living without these predators. However, high fish-predation sites are generally farther downstream than low fish-predation sites, and so may also differ in physical habitat features related to stream size, as well as in the abundance of predatory prawns ( Macrobrachium crenulatum ). The goal of our study was to disentangle the effects of fish predation on colour evolution from the potential effects of physical habitat features and predation by prawns. We collected 20 male guppies from each of 29 sites in two Trinidadian rivers. We then quantified the colour pattern of these fish; each spot was measured for size and assigned to a colour category. For each site, we determined the fish predation regime and quantified stream size, water colour, canopy openness, and prawn abundance. We then used regressions to assess the relative importance of these factors in explaining variation in guppy colour. Supporting previous work, the presence of predatory fishes was the most important explanatory variable for many components of colour pattern. Physical habitat features explained some of the remaining variation, but in inconsistent ways between the two rivers. The abundance of predatory prawns also explained variation in male colour. Our results suggest that predatory fishes impose the strongest selection on the colour pattern of male guppies but that other factors are also important.     

Deficient colour vision and interpretation of histopathology slides: cross sectional study.

OBJECTIVE: To determine whether histopathologists with deficient colour vision make more errors in slide interpretation than those with normal colour vision. DESIGN: Examination of projected transparencies of histopathological slides under standardised conditions by subjects whose colour discriminating ability was accurately assessed. SETTING: Departments of histopathology in 45 hospitals in the United Kingdom. SUBJECTS: 270 male histopathologists and medical laboratory scientific officers. MAIN OUTCOME MEASURES: Number of slides correctly identified by subjects whose colour vision was measured on the Ishihara, City University, and Farnsworth-Munsell 100 hue tests. RESULTS: Mean (SD) scores (out of 10) for doctors with colour deficient vision were 9.4 (0.7) v 9.9 (0.4) for controls (P < 0.01) and 7.5 (1.6) v 9.4 (0.7) for scientific officers (P < 0.001). When subjects with colour deficient vision were categorised into severe, moderate, or mild, there was a significant trend towards those with severe deficiency making more mistakes (P < 0.001). CONCLUSIONS: Histopathologists and medical laboratory scientific officers should have their colour vision tested; if they are found to have a severe protan or deutan deficiency, they should be advised to adopt a safe system of working.     

In vivo sucrose stimulation of colour change in citrus fruit epicarps: Interactions between nutritional and hormonal signals

During ripening, citrus fruit-peel undergoes 'colour break', a process characterized by the conversion of chloroplast to chromoplast. The process involves the progressive loss of chlorophylls and the gain of carotenoids, changing peel colour from green to orange. In the present work, the in vivo and in vitro effects of supplemented nutrients (sucrose and nitrogen) and phytohormones (gibberellins [GA] and ethylene) on colour change in fruit epicarp of Satsuma mandarin ( Citrus unshiu (Mak.) Marc., cv. Okitsu), were studied. The rate of colour break was correlated positively with sucrose content and negatively with nitrogen content. The removal of leaves blocked natural sucrose build-up and nitrogen reduction in the peel. Defoliation also inhibited chlorophyll disappearance and carotenoid accumulation, thereby preventing colour break. In vivo sucrose supplementation promoted sucrose accumulation and advanced colour break. In both in vivo and in vitro experiments, colour change promoted by sucrose was unaffected by ethylene but delayed by GA_3. In non-supplemented plants, ethylene accelerated colour break while GA₃ had no detectable effects. Ethylene inhibitors effectively counteracted the sucrose effects on colour change. Collectively, these results suggest that the chloroplast to chromoplast conversion in citrus fruit epicarps is stimulated by sucrose accumulation. The sugar regulation appears to operate via ethylene, whereas GA may act as a repressor of the sucrose-ethylene stimulation.     

Poor environmental tracking can make extinction risk insensitive to the colour of environmental noise

The relative importance of environmental colour for extinction risk compared with other aspects of environmental noise (mean and interannual variability) is poorly understood. Such knowledge is currently relevant, as climate change can cause the mean, variability and temporal autocorrelation of environmental variables to change. Here, we predict that the extinction risk of a shorebird population increases with the colour of a key environmental variable: winter temperature. However, the effect is weak compared with the impact of changes in the mean and interannual variability of temperature. Extinction risk was largely insensitive to noise colour, because demographic rates are poor in tracking the colour of the environment. We show that three mechanisms-which probably act in many species-can cause poor environmental tracking: (i) demographic rates that depend nonlinearly on environmental variables filter the noise colour, (ii) demographic rates typically depend on several environmental signals that do not change colour synchronously, and (iii) demographic stochasticity whitens the colour of demographic rates at low population size. We argue that the common practice of assuming perfect environmental tracking may result in overemphasizing the importance of noise colour for extinction risk. Consequently, ignoring environmental autocorrelation in population viability analysis could be less problematic than generally thought.     

The environmental control of colouration in a bushcricket, Mygalopsis marki Bailey (Orthoptera: Tettigoniidae)

The environmental factors proximately influencing variable colouration in the bushcricket, Mygalopsis marki , were studied in natural populations and under controlled laboratory conditions. Two major components of variable colouration were identified; a green/brown dimorphism in ground colour hue (dominant wave length) and continuous variation in the darkness of brown insects, representing a contrast between ground colour value (brightness) and the intensity of overlying black pattern. Ground colour hue differed between natural populations in different seasons and at different localities. The proportion of brown individuals was greater in populations developing over late summer than over spring at the same locality, and in populations from drier localities, as indicated by vegetation type, in the same season. Experimental studies showed that colour change occurred at moults, with green colouration promoted by increased water intake in developing nymphs. Ground colour value and pattern differed between natural populations at different localities, but not in different seasons. Ground colour value was less, and pattern was greater, in populations from localities with a dense cover of forbs and grasses. Experimental studies showed that ground colour value and pattern were influenced by the intensity of incident radiation received by developing nymphs, with decreased intensity promoting lower value and greater pattern.     

Retention time as a primary determinant of colour and light attenuation in two tropical Australian reservoirs

1. The light climates of Darwin River Reservoir (DRR) and Manton River Reservoir (MRR), in northern Australia, are compared for an 8-year period. The reservoirs are subject to the same wet/dry tropical climate and have similar catchment characteristics, but differ in their basin morphology, retention time and trophic status.
2. Median euphotic depths in DRR and MRR were 9.7 and 4.4 m, respectively. Seasonal variation in each reservoir's euphotic depth was best explained by colour, based on a stepwise linear regression. Turbidity was excluded from the two regressions, while chlorophyll a concentration was significant only for the MRR regression.
3. Both reservoirs showed the same seasonal pattern for colour. Wet season inflow increased reservoir colour, and was followed by a reduction in colour due to photodegradation and microbial decomposition of humic material, reaching a minimum before the next wet seasons inflow.
4. Although the colour of catchment run-off into both reservoirs was similar, MRR colour was two to three times greater than that measured in DRR. The higher colour and greater light attenuation of MRR is attributed primarily to its shorter retention time, and therefore shorter time for colour removal. Annual retention time accounted for 97% of the variability of average annual colour (measured as absorption at 440 nm), based on a linear regression of log₁₀ transformed data for both reservoirs.
5. Long retention times favour reduced colour, increasing water transparency, particularly in water bodies of low trophic state and inorganic turbidity.     

Retention time as a primary determinant of colour and light attenuation in two tropical Australian reservoirs

1. The light climates of Darwin River Reservoir (DRR) and Manton River Reservoir (MRR), in northern Australia, are compared for an 8-year period. The reservoirs are subject to the same wet/dry tropical climate and have similar catchment characteristics, but differ in their basin morphology, retention time and trophic status.
2. Median euphotic depths in DRR and MRR were 9.7 and 4.4 m, respectively. Seasonal variation in each reservoir's euphotic depth was best explained by colour, based on a stepwise linear regression. Turbidity was excluded from the two regressions, while chlorophyll a concentration was significant only for the MRR regression.
3. Both reservoirs showed the same seasonal pattern for colour. Wet season inflow increased reservoir colour, and was followed by a reduction in colour due to photodegradation and microbial decomposition of humic material, reaching a minimum before the next wet seasons inflow.
4. Although the colour of catchment run-off into both reservoirs was similar, MRR colour was two to three times greater than that measured in DRR. The higher colour and greater light attenuation of MRR is attributed primarily to its shorter retention time, and therefore shorter time for colour removal. Annual retention time accounted for 97% of the variability of average annual colour (measured as absorption at 440 nm), based on a linear regression of log₁₀ transformed data for both reservoirs.
5. Long retention times favour reduced colour, increasing water transparency, particularly in water bodies of low trophic state and inorganic turbidity.