Rate Of Color Change Research Articles

Evaluation of the metabolic diversity of microbial communities in four different filter layers of a constructed wetland with vertical flow by Biolog™ analysis

The community-level substrate utilization test based on direct incubation of environmental samples in Biolog EcoPlates™ is a suitable and sensitive tool to characterize microbial communities. The aim of this study was to investigate the influence of plant roots and soil structure on the metabolic diversity of microorganisms in a constructed wetland with vertical flow. Sediment samples were taken from different filter depths representing specific filter layers. The color development representing the substrate utilization was measured with the samples over a period of 10 days. The average well color development (AWCD) for all carbon sources was calculated as an indicator of total activity and in order to compensate the influence of the inoculum's density on the color development in the plates. After transformation by dividing by the AWCD, the optical density data were analysed by principal component analysis (PCA). An analysis of the kinetic profile of the AWCD was carried out to increase the analytical power of the method. The corrected data have been successfully fit to the logistic growth equation. Three kinetic model parameters, the asymptote ( K), the exponential rate of color change ( p) and the time to the midpoint of the exponential portion of the curve ( s), were used for statistical analysis of the physiological profile of the microbial community in the different filter layers of the constructed wetland. We found out that in the upper two horizons, which were rooted most densely, mainly easily degradable materials like specific carbohydrates were utilized, while in the lower layers, where only single roots occur, more biochemically inert compounds, e.g. 2-hydroxy benzoic acid, were utilized. Furthermore it could be shown that microorganisms in the surface layer benefited from the plant litter because they can utilize decay products of these. In the lower filter layers specialists took advantage because they had to cope with the biochemically inert materials and the lower nutrient supply.

Faba bean (Vicia faba L.) seeds darken rapidly and phenolic content falls when stored at higher temperature, moisture and light intensity

Faba beans cv. Fiesta with seed moisture content (SMC) modified to 8, 10, 12 and 14% were packed in polyethylene lined aluminium foil bags and stored at 5, 15, 20, 25, 30, 37, 45, 50 or 60 °C (± 2 °C) for one year. Samples were analysed for moisture content and seed coat (testa) colour over the storage period using a chroma meter. A continuous increase in L∗ and b∗ values was found in all samples with the passage of time whereas a∗ values first increased and then decreased in samples stored at relatively high temperatures (≥ 37 °C). The initial beige testa colour changed to light brown, dark reddish-brown or almost black depending on storage conditions. The higher the temperature and SMC the faster the rate of change in colour (▵Eab∗ values). Seeds with 8% SMC had more stable testa colour compared to seeds with higher SMC. Exposure to artificial light (350 μ mol m−2 s−1) substantially accelerated the colour darkening. Cotyledons stored at 37 ± 2 °C also darkened with the storage time. A loss in total free phenolics, total tannins and proanthocyanidins was found with increased darkness of testa and cotyledons during storage.

Alternating frequency to increase the response to stimulation from medium voltage electrical stimulation and the effect on objective meat quality

The use of alternating frequencies during stimulation can increase stimulation response of a medium voltage electrical stimulation unit (MVS) by increasing the rate of pH decline. Various combinations of frequency modulation were tested in experiment 1 to determine the treatment resulting in the greatest stimulation response; the lowest initial pH, fastest rate of pH decline, highest temperature at pH 6 and the highest number of carcasses with a pH of 6 by 25 oC and the treatment achieving the highest number of carcasses in the pH temp window (temperature at pH 6 between 18-25 oC). The objective meat quality of these treatments compared to an unstimulated treatment was tested in experiment 2. Modulating the frequency (Hz) across the 6 segmented electrodes of the MVS by 10, 15, 25, 10, 15, 25 Hz (Treatment 6, using a pulse width: 2.5 ms, current: 1 A) resulted in the greatest stimulation response. This treatment may be suitable for abattoirs that hot bone sheepmeat and require fast pH declines to ensure minimal cold shortening of meat. However, this treatment did not result in the tenderer meat despite the higher stimulation response. This treatment may have induced a greater number of contractions overall and therefore a greater pH decline response but resulted in less myofibrillar disruption compared to the other treatments due to a concomitant decreased force of contraction thus reducing potential tenderisation. Maintaining a constant frequency of 15 Hz (Treatment 1; pulse width: 2.5 ms, current: 1 A) resulted in a higher number of carcasses in the pH temp window required (temperature at pH 6 between 18–25 oC) in part A ( P < 0.05) and in addition to the higher tenderness levels this treatment may be more appropriate to satisfy the overall demands of abattoirs using these systems. This paper has also demonstrated electrical stimulation results in tenderer meat compared to unstimulated meat even after 30 d of ageing (2.53 ± 0.4 compared to 2.85 ± 0.1 for the loin ( M. longissimus thoracis et lumborum) ( P < 0.01) possibly due to a protective benefit of stimulation on meat tenderness. Overall, no detrimental effects of modulating frequency were observed on drip loss or retail colour display despite a greater rate of colour change observed with the modulated frequency treatment and the longer aged product.

Fadable ink for time–temperature control of food freshness: Novel new time–temperature indicator

A novel new colorimetric time–temperature indicator, based on fadable ink has been developed. The printed sign is able to disappear in a defined time period. The color fading is based on the red-ox properties of anthraquinone derivative. Beige anthraquinone β-sulfonate can be easily reduced by sodium hydrosulfite and become red color. By contacting with oxygen, the red color turns back into beige. The time–temperature indicator comprises three thin layers materials either on paper or plastic substrate. The rate of color change is varied by the chemical composition of the polyacrylate. This multilayer structure time–temperature indicator can be easily made by knife coater and screen printing. The made indicator should be very useful to monitor freshness of food.

Evaluation of degradation on Nylon‐6 and Nylon‐6/montmorillonite nanocomposite by color measurement

AbstractAn evaluation of degraded level is an important subject for industrial products. Ordinarily, many kinds of polymer material changes its color through the degrading process by altering its chemical structure, and IR and UV are applicable to ensure the production of the functional groups. However, these methods are hardly applicable to measurements of product on site without the sample collection. A spectrophotometer is sufficiently lightweight, compact, and capable of measurements on site without the sample collection. With these backgrounds, the correlation of the color with the tensile strength and the molecular weight was studied by using the spectrophotometer. Through the thermal aging test at various temperatures, specimens became yellowish and the increase rate of color change was different between neat Nylon‐6 and Nylon‐6 nanocomposite. Such changes were closely related to the tensile strength and the molecular weight. As a method to evaluate the polymer degradation, the correlation of the difference of yellowness index (ΔYI) with the tensile strength and the molecular weight was sufficiently high and the ΔYI indicated a difference between neat Nylon‐6 and Nylon‐6 nanocomposite. From these results, it is found that the color measurement with the spectrophotometer is a practical method for evaluation of polymer degradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Postharvest handling and storage of the edible red seaweed Gracilaria

Red macro-algae ( Gracilaria spp.) are used as a fresh food in Hawaii. Species commonly marketed include G. coronopifolia, G. parvispora, G. salicornia and G. tikvahiae, however, these seaweeds have a short postharvest life of about 4 d. This research was undertaken to determine the changes that occur postharvest and how the postharvest life of G. salicornia can be extended. The changes in color, phycobilins, respiration rate, ethylene production, protein content, leakage and ion thalli content were determined. Postharvest effects of storage temperature, light/dark storage, modified atmospheres, calcium and nitrogen nutrient treatments, chlorine and heat treatments were evaluated to extend storage life and minimize microbial growth. When stored overnight at 2 °C, thalli became limp and entirely pinkish-red indicating possible chilling injury. At 10 °C, the color change and decline in phycobilin content occurred in 2 d and by the 4th day more than 90% of the thalli were either pink or red, and the phycobilin content had declined by 50%. At 12.5 °C and higher storage temperatures, the rate of color change was similar and the optimal storage temperature was between 15 and 17 °C in the dark. This storage temperature maintained quality but did not extend overall postharvest life. A steady rise in respiration rate occurred when stored in the dark or in the light. Light seemed to stimulate respiration rate when stored at 16 °C, but not at 21 °C. No relationship was found between ethylene production and respiration rate either with or without light exposure during storage. Ethylene production did not appear to be related to any physiological changes. Light did increase the rate at which thalli turned pink. Seaweed submerged in seawater in the dark had an extended postharvest life of about 30 d. Treatment with chlorine (50 mg L −1) to minimize microbial growth was phytotoxic. Neither a 2 nor a 60 min postharvest dip in artificial seawater supplemented with 1 or 10 mM calcium, potassium, sodium, ammonium as the nitrate salt extend postharvest life. Treating G. parvispora and G. tikvahiae with hot seawater at 42 °C for 5 min was beneficial in maintaining appearance and extended postharvest life 40–60%. Storage at 15 °C and submerged in seawater or treated at 42 °C for 5 min depending upon species, showed potential at increasing postharvest life of red seaweed.

Microstructure affects the rate of chemical, physical and color changes during storage of dried apple discs

Blanching, freezing and drying induce major changes in the physical properties of processed foods. Microstructural changes induced by these processes in apple discs were related to the degree and kinetics of browning and to fracture mechanics after drying and later storage at 70 °C under a wide range of relative humidity (RH). Blanched and unblanched apple discs were dehydrated by vacuum drying or freeze-drying to induce the formation of different structures, then equilibrated from 33% to 75% RH and stored at 70 °C in order to promote browning. Color changes on the surface of apple discs were analyzed non-invasively by image analysis using a computerized vision system. Pre-treatments and drying conditions modified the structural characteristics of apple discs, which in turn, changed sorption properties, texture hardness and browning development. Microstructural changes (e.g., loss of cellular integrity) promoted higher browning rates, the rate and degree of browning was analyzed.

Non-Base Pairing DNA Provides a New Dimension for Controlling Aptamer-Linked Nanoparticles and Sensors

DNA aptamers have been recently applied as simple and fast colorimetric sensors for a wide range of molecules. A unique feature of these systems is the presence of non-base pairing oligonucleotides in both DNA aptamers and spacers on DNA-functionalized nanoparticles. We report here a systematic investigation on an adenosine aptamer-linked gold nanoparticle system. When the aptamer overhang and the spacer were aligned on the same side, adenosine-responsive disassembly was inhibited. This inhibition effect increased with the length of the spacer, and fully inhibited activity was observed with the spacer containing more than three nucleotides. In contrast to a linear relationship between the spacer length and melting temperature in double-stranded DNA systems without overhangs, the aptamer system displayed a nonlinear relationship, with the melting temperature decreasing exponentially with spacer length. Control experiments suggested that this inhibition effect was due to thermodynamic factors rather than kinetic traps. A comparison with aptamer beacon systems indicated that nanoparticles may play an important role in this inhibition effect, and no specific interactions between the aptamer overhang and spacer were detected. The identity of nucleotides in the spacer did not affect the conclusions. Furthermore, the rate of disassembly or color change was slower at lower temperature or higher ionic strength, but was little affected by pH from 5.2 to 9.2. Therefore, non-base pairing DNA provided another dimension for controlling DNA-linked nanoparticles in addition to pH, temperature, or ionic strength, and this knowledge has resulted in the most optimal construct for sensing applications.

Preparation and photochromic properties of NiAl-NO3-LDHs/LDPE composite

Nanoscale NiAl-NO3-LDHs with good crystallinity have been synthesized by a method, Separate Nucleation and Aging Steps (SNAS). An NiAl-NO3-LDHs/LDPE composite was prepared by blending NiAl-NO3-LDHs and LDPE in a heated double-roller mixer. The color of this composite changed from olive green to steel gray under UV irradiation. After heating at 80°C for 2 h, the color returned to olive green. The effect of varying the amount of added NiAl-NO3-LDHs and UV exposure time on the photochromic properties of the composite has been investigated. The results showed that the photochromic phenomenon becomes more apparent with increasing amount of NiAl-NO3-LDHs. When the amount reaches 5%, the composite exhibits good photochromic properties and reproducibility. The color change rate of the composite reaches a maximum when the irradiation time exceeds 20 min. The addition of LDPE improves the photochromic cyclability of NiAl-NO3-LDHs significantly. The addition of nanoscale NiAl-NO3-LDHs also improves the mechanical properties of LDPE to some extent.

Effect of lamb age and electrical stimulation on the colour stability of fresh lamb meat

The aim of this experiment was to compare the effects of electrical stimulation and lamb age on the retail colour stability of lamb meat. Poll Dorset Merino crossbred lambs that were 5 months (‘suckers’, SU) and 12 months (‘carryovers’, CO) finished on the same green annual pasture were slaughtered at a commercial abattoir. Half of the carcasses in each age group (10) were either electrically stimulated (ES) or not stimulated (NES) post-dressing with a commercial high voltage electrical stimulation system. Luminescence (L), hue angle (indication of redness), chroma (intensity), and oxy/met (a measure of browning) values were measured at 0 h (0 days), 21 h (0.86 days), 93 h (3.88 days), and 166 h (6.91 days) after meat had been cut 1 day after slaughter, over wrapped, and put under simulated retail display conditions. Three muscles, m. longissimus thoracis et lumborum (LL), m. gluteus medias (GM), and m. rectus femoris (RF), were measured in this way. A linear mixed model was used to fit a repeated-measurements model to the light measurements of L, hue angle, chroma, and oxy/met. Oxy/met rate of change was compared by fitting splines to predict the time required for oxy/met to reach an arbitrary benchmark value of 3. Colour and rate of colour change during display were affected by both age class and electrical stimulation but these effects depended on the muscle. The LL was the darkest (lowest L) and reddest (lowest hue angle), whilst RF was the most stable in colour (lowest rate of change for oxy/met) of the 3 muscles tested. Age class had a greater effect on oxy/met rate of change for the LL and GM compared with RF. Oxy/met of LL changed more rapidly for CO than SU lambs. ES increased the time for oxy/met to reach 3 in RF and GM for SU only but did so for both age groups in LL. ES decreased this time in RF and GM for CO. CO meat contained a higher concentration of myoglobin than SU meat. Negative effects of electrical stimulation on colour stability are more likely to occur in older lambs and in the GM and RF rather than in the LL.

Multi-Variant Analysis of Real-World Environmental Variables Affecting Image Fading on an Outdoor Synthetic Inkjet Substrate

The permanence of large format, outdoor inkjet signs is a concern for many museums and companies creating signs that will be displayed for years or months either on the side of a museum or by the side of the road. The permanence industry has focused their research on using equipment to simulate the outdoor conditions these prints face to gauge their fading properties. The research conducted here took a more direct approach by placing the prints in an actual outdoor environment situation with no protection, tracking the rate of color change (DE), and the fluctuation of the environmental variables. A multiple regression analysis of the data that was collected was then used to create prediction formulas and to eliminate environmental variables that did not affect the fading.The multiple regression analysis was able to create a prediction formula for only two of the color patches tested on the uncoated vinyl substrate. The test included an uncoated vinyl substrate patch and nine printed color patches (cyan, magenta, yellow, black, red, green, blue, and two grays). The successful formulas created were for the measured substrate patch and the cyan patch. The formula showed that the substrate patch was affected by the average high and low temperatures and by the amount of time exposed in weeks. A second formula showed that the cyan patch was affected by the UV (ultra violet) index and the amount of time exposed in weeks.The prediction formulas act as more of a guideline for museums or printers to base their decisions about which substrates to use and to provide an idea about what environmental factors can be expected to affect the fading. This can in turn aid future research into the permanence of synthetic inkjet substrates by allowing researchers to conduct a preliminary short term study to narrow down the different variables they will be using for a more in-depth study. This research has shown that it is possible to conduct a short-term study of several variables to be used as a basis for later, more advanced research of the same material but with fewer variables, or for accelerated testing.

P42 A Simple Test for the Differential of Maternal and Fetal Bloods

The structure of fetal haemoglobin (HbF) differs to that of adult haemoglobin (HbA) and protects it from denaturing when subjected to a pH change. With this knowledge, Apt et al1 adjusted the pH of the meconium, in melena neonatorium, by the addition of NaOH, and noted that a change of colour to green from pink occurred only if HbA was present. By utilising the same principle, the process can be modified to confirm the source of blood samples requested for the investigation of a possible fetomaternal haemorrhage, post delivery, for the prevention of Rhesus haemolytic disease of the newborn. 10 adult male bloods and six cord samples were used as the test material for the investigation. The rate at which the colour changed from pink to green of the test material was measured over a range of variables. The haematicrit was artificially adjusted between 30% and packed cells, with a permutation of volumes from 10 to 500 μL added to NaOH at concentrations between 0.05 M and 3 M.Results The optimum NaOH concentration was 0.1 M, equating to a pH 13.0 The haematicrit showed no influence on the reaction, but packed cells were chosen as the easiest to reproduce for consistency. The rate of colour change from pink to green took a maximum 1 min. Contamination of maternal with fetal bloods, and visa versa, at a low ratio is undetectable and at a high ratio gives a visual chimera of colour and intact erythrocytes.Method Using the above data a simple routine laboratory method of adding 100 μL of packed cells to 0.5 mL of 0.1 M NaOH, rapid mixing, and observing for a colour change between 1 min and a maximum of 10 mins. Pink to green show the blood to maternal i.e. HbA, but remaining pink indicative of HbF. The simultaneous testing of blood from and adult male and known cord blood, provides a positive and negative control respectively. This simple test has been extensively used to verify which are maternal and cord samples, when both express the same ABO and Rh(D) blood groups.1. Apt L, Downey WS Jr. (1953) Melena neonatorium: the swallowed‐blood syndrome. AMA Am J Dis Child.; 86(5): 639; discussion, 639–40.

Pre- and Postharvest Treatments to Control Green Mold of Citrus Fruit During Ethylene Degreening.

Two approaches, fungicide applications to trees before harvest and drenching fruit after harvest, were evaluated to minimize postharvest green mold, caused by Penicillium digitatum, particularly among fruit subjected to ethylene gas after harvest, a practice termed "degreening" that eliminates green rind color. Preharvest applications of thiophanate methyl (TM) controlled postharvest green mold consistently. In five tests, green mold among degreened orange fruit was 16% when TM was applied 1 week before harvest; whereas, among fruit not treated, the incidence was 89.5%. Thiabendazole (TBZ) applied to harvested fruit in bins before degreening also was very effective. TBZ effectiveness was enhanced by mild heating (41°C), adding sodium bicarbonate, and immersing fruit, rather than drenching them, with the solution. With these measures, an isolate of P. digitatum with a high level of TBZ resistance was significantly controlled. In semicommercial tests with naturally inoculated fruit, TBZ and sodium bicarbonate treatment reduced green mold incidence from 11% among untreated orange fruit to 2%. TBZ residues in lemon fruit at 41°C were about twice those treated at 24°C. Neither TM before harvest nor TBZ and sodium bicarbonate applied after harvest influenced green color removal during degreening of orange fruit. Sodium bicarbonate slightly reduced the rate of lemon color change.

Monitoring with reflectance spectroscopy the colour change of PVC plastisol coated strip steel due to weathering

Weathering can cause colour changes in pigmented PVC plastisol coatings. The rate of colour change is dependent on a number of factors, such as PVC resin, pigment type and concentration, and local climate. In this paper, an investigation into the mechanisms that cause these colour changes is reported. The investigation involves a set of 350 paints, based on a typical plastisol formulation, that has been exposed to natural weathering at sites in Lancashire and Sussex in the UK, and to accelerated weathering using QUV testers with UVA-340 lamps and condensation cycles. Colour changes were measured using a Gretag SPM50 reflectance spectrophotometer. It was found that the reflectance spectra measured in this way provided a more potent tool for investigating the chemical reactions that cause discolouration in coatings during weathering than the CIE L*a*b*parameters that are normally used to describe colour changes.Reflectance spectroscopy has been shown to facilitate the correlation between natural weathering and accelerated weathering, by giving a better understanding of the prevalent chemical processes that take place in the coatings during different accelerated weathering programmes (with and without condensation) and with natural weathering at different locations (high UV climates and higher rainfall climates). Phenomena such as PVC dehydrochlorination and organic pigment degradation could be analysed conveniently using reflectance spectrophotometry.

EFFECTS OF LIGHT AND TEMPERATURE ON COLOUR CHANGES IN RIPENING FRUIT OF ACTINIDIA MACROSPERMA

Unripe, green fruit of Actinidia macrosperma turn an intense orange during ripening on the vine or after harvest. The change in colour is due to degradation of chlorophyll and synthesis of carotenoids. Temperature and light can influence the rate of colour change during storage of the fruit. Fruit harvested green and then stored at room temperature (c. 20°C) quickly turned a bright orange colour, irrespective of light regime. Green fruit stored at 4°C did not turn orange but instead became white or pale yellow over a period of 10 weeks. If these fruit were then shifted to room temperature, they rapidly turned bright orange. Changes in fruit colour during storage appear to be affected more by temperature than by light. It is concluded that carotenoid biosynthesis is more strongly affected by temperature than is chlorophyll degradation.

Fruit Quality, Fermentation Products, and Activities of Associated Enzymes During Elevated CO2 Treatment of Strawberry Fruit at High and Low Temperatures

The effects of postharvest treatments of air and 20 kPa CO2 (in air) at 2 or 20 °C on color, firmness, accumulations of acetaldehyde, ethanol, and ethyl acetate, activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity, and expression of an ADH gene were studied in strawberry fruit (Fragaria ×ananassa Duch. cv. Jewel). CO2 treatment enhanced strawberry fruit firmness at 2 °C but not 20 °C, while the rate of color changes was affected by CO2 treatment at 20 °C but not at 2 °C. Temperature also affected the accumulation of acetaldehyde, ethanol and ethyl acetate in CO2-treated fruit. All three compounds accumulated in fruits at 2 °C. At 20 °C, ethanol accumulated slightly by day 6, although ethyl acetate accumulated in fruit from both atmospheres. PDC enzyme activity was higher in CO2-treated fruit than their air-treated control at 2 °C but not at 20 °C. ADH activity and ADH mRNA accumulation of the CO2-treated berries were higher than in air at 20 °C but not 2 °C. The results, overall, indicate that patterns of change among gene expression, enzyme activities, and fermentation product accumulation were not consistent.

Size and Temperature Dependence of Surface Plasmon Absorption of Gold Nanoparticles Induced by Tris(2,2‘-bipyridine)ruthenium(II)

It is well known that surface plasmon absorption (color) of Au nanoparticles highly depends on its size, shape, and surrounding surface environment, providing a great opportunity for the development of Au nanoparticles as a probe for chemical and biochemical sensing and as a building block for nano-optical devices. Currently, it remains incompletely understood how the surface properties of Au nanoparticles ultimately define its optical properties, hindering the progress of rational design of Au nanoparticles for biochemical sensing and assembly of nano-optical devices. Ru(bpy)32+ possesses rich photochemical and electrochemical properties, offering a unique probe to study the surface environment of Au nanoparticles. In this study, we investigate the kinetics of surface plasmon absorption of Au nanoparticles (6.5, 19, 48, 97 nm) in the presence of Ru(bpy)32+ at 24.0, 33.0, and 51.0 °C. We find that the color-change rate of Au nanoparticles is highly sensitive to the amount of Ru(bpy)32+. In addition, the m...

The control of color change in the Pacific tree frog, Hyla regilla

A number of environmental variables have been identified as affecting anuran color, but rarely have the interactions between these variables been investigated. In attempt to elucidate the function of color change, we conducted a within-subject, full factorial experiment designed to determine the simple and interactive effects of background, temperature, and light intensity on the rate of color change in the Pacific tree frog (Hyla regilla Baird and Girard, 1852). Color was investigated holistically, as well as by decomposing it into its constituent parts (hue, chroma, and lightness), using digital photography. The rate of color change was faster on the green versus the brown background, at 10 versus 25 °C, and at low versus high light intensity. There was also a significant effect of the interaction between background color and temperature on the rate of color change. We found increased rates of hue, chroma, lightness, and color change with increasing initial hue, chroma, lightness, and color distances between the Pacific tree frog and its background, respectively. In addition, initial color distance covaried with changes in environmental variables. After controlling for initial color distance, and thus the effects of background matching, background color and temperature still showed a significant interaction for their effects on rate of color change. These results suggest that crypsis (i.e., background matching) is not the only function of physiological color change in H. regilla. Physiological color change may also be used to hydro- and (or) thermo-regulate.

Diplostomum spathaceum metacercarial infection and colour change in salmonid fish.

Colour changes in two salmonid fish, the salmon (Salmo salar) and sea trout (S. trutta), were examined in relation to infection with the trematode Diplostomum spathaceum. This parasite had no effect on the rate of colour change in these fish, although species specific differences in colour adjustment times were observed. Increasing asymmetry in parasite numbers between the right and left eye, which could lead to the retention of vision in one eye, nevertheless tended to reduce the colour change time in salmon with moderate infection (P=0.08). This first experimental attempt to examine colour changes in fish in relation to eye fluke infections provides grounds for future investigations. The darker appearance of the heavily infected fish described in the literature suggests that a high parasite burden actually causes colour changes. We emphasise that detailed quantitative studies using fish with higher parasite loads, especially from the tail of the aggregated parasite distribution, are needed to describe these relationships in detail.

Photoperiodic and temperature control of diapause induction and colour change in the southern green stink bug Nezara viridula

Abstract. The effect of photoperiod and temperature on the duration of the nymphal period, diapause induction and colour change in adults of Nezara viridula (L.) (Heteroptera: Pentatomidae) from Japan was studied in the laboratory. At 20 °C, the developmental period for nymphs was significantly shorter under LD 10 : 14 h (short day) and LD 16 : 8 h (long day) than under intermediate photoperiods, whereas at 25 °C it was slightly shorter under intermediate than short‐ and long‐day conditions. It is assumed that photoperiod‐mediated acceleration of nymphal growth takes place in autumn when day‐length is short and it is unlikely that nymphal development is affected by day‐length under summer long‐day and hot conditions. Nezara viridula has an adult diapause controlled by a long‐day photoperiodic response. At 20 °C and 25 °C in both sexes, photoperiodic responses were similar and had thresholds close to 12.5 h, thus suggesting that the response is thermostable within this range of temperatures and day‐length plays a leading role in diapause induction. Precopulation and preoviposition periods were significantly longer under near‐critical regimes than under long‐day ones. Short‐day and near‐critical photoperiods induced a gradual change of adult colour from green to brown/russet. The rate of colour change was significantly higher under LD 10 : 14 h than under LD 13 : 11 h, suggesting that the colour change is strongly associated with diapause induction. The incidences of diapause or dark colour did not vary among genetically determined colour morphs, indicating that these morphs have a similar tendency to enter diapause and change colour in response to short‐day conditions.