Coho Salmon (Oncorhynchus kisutch) Prefer and Are Less Aggressive in Darker Environments

Fish are capable of excellent vision and can be profoundly influenced by the visual properties of their environment. Ambient colours have been found to affect growth, survival, aggression and reproduction, but the effect of background darkness (i.e., the darkness vs. lightness of the background) on preference and aggression has not been evaluated systematically. One-hundred Coho salmon (Oncorhynchus kisutch), a species that is increasing in popularity in aquaculture, were randomly assigned to 10 tanks. Using a Latin-square design, every tank was bisected to allow fish in each tank to choose between all the following colour choices (8 choices in total): black vs. white, light grey, dark grey, and a mixed dark grey/black pattern, as well as industry-standard blue vs. white, light grey, dark grey, and black. Fish showed a strong preference for black backgrounds over all other options (p < 0.01). Across tests, preference strength increased with background darkness (p < 0.0001). Moreover, having darker backgrounds in the environment resulted in less aggressive behaviour throughout the tank (p < 0.0001). These results provide the first evidence that darker tanks are preferred by and decrease aggression in salmonids, which points to the welfare benefits of housing farmed salmon in enclosures containing dark backgrounds.     

The effects of spinal nerve section on responses of melanophores in the minnow, Phoxinus phoxinus(L.)

A continuous observation apparatus was used to study the responses of Phoxinus phoxinus melanophores to illuminated black/white backgrounds and their reversal. The fish. Although confined, showed maximum melanosome dispersion (MI 5) and maximum melanosome aggregation (MI 1) when exposed to illuminated black and white backgrounds respectively. Melanophores affected by spinal nerve section showed full melanosome dispersion and the affected area appeared as a black band. The affected melanophores marginally and gradually aggregated their melanosomes if the fish was exposed to an illuminated white background for about a week. The responses of these melanophores to illuminated black and white backgrounds and their reversal indicates that the dispersal of their melanosomes in response to a black background is much faster than their aggregation in response to a white background. It is concluded that an active mechanism is involved and possible factors controlling it are discussed.     

Structural studies of nerve terminals containing melanin-concentrating hormone in the eel,Anguilla anguilla

Summary Eels were adapted to black- or white-coloured backgrounds and the pituitary glands were prepared for light and electron microscopy. Immunocytochemical staining was used to study the distribution of the neurohypophysial melanin-concentrating hormone in the neurointermediate lobe. The hormone was located in small, elliptical, electron-opaque neurosecretory granules, measuring approximately 120×90 nm. The neurones terminated on blood vessels in the centre of the neurohypophysis and on the basement membrane separating neural and intermediate lobe tissues. The results of both light and electron immunocytochemistry and of radioimmunoassay are consistent with a higher rate of hormone release from eels adapted to white backgrounds than from those adapted to black backgrounds. In addition to this, when fish that had been adapted to white tanks were transferred to black tanks, there was an accumulation of irMCH in the gland and an increased numerical density of secretory granules at nerve terminals. These results reinforce the proposal that MCH is released during adaptation to a white background, to cause melanin concentration and to inhibit MSH release, and that its release is halted in black-adapted fish.     

Background colouration influences body colour segregation in mollies

When given a choice of swimming against a black background near an empty black end compartment or swimming against a white background near an empty white compartment, black morph mollies Poecilia latipinna spent significantly more time against the black background. The presence of a shoal (either white or black mollies) in the black compartment increased the preference of the test fish for the black background. However, black molly test fish spent significantly less time against a black background if a black shoal was present in the white compartment than in assays in which a white shoal was in the white compartment. In assays where test fish were given the choice between two black shoals, test fish spent significantly more time near the black shoal on the black background. Similarly, when given the choice between two white shoals, test fish spent significantly more time against the black background. The results suggest that the presence of cryptic backgrounds alter shoalmate choices in fish that assort according to body colouration.     

STX17在不同毛色小鼠皮肤中差异表达与在毛囊中的定位

突触融合蛋白17 (STX17)是一种囊泡蛋白,参与细胞中物质的运输.为研究Stx17在不同毛色皮肤中是否存在差异表达及明确它在毛囊中的定位,进行了普通PCR、real-time PCR、免疫组化和蛋白免疫印迹实验对小鼠皮肤组织和体外培养黑素细胞的Stx17基因及蛋白的检测.普通PCR检测得出小鼠皮肤和黑色素细胞总RNA有Stx17 CDS区序列的表达;荧光定量检测显示,在白、灰、黑3种组织中Stx17均有表达,在灰色腹部表达量最高,是黑色皮肤的1.682倍,昆明鼠白色皮肤中表达量最低,是黑色皮肤的0.115倍;皮肤组织免疫组化结果显示,STX17表达于毛囊的上皮根鞘,且毛囊上段和中段表达量高于下段,黑色素细胞的免疫组化分析得出,STX17在黑色素细胞的细胞质和细胞膜上均有表达;蛋白免疫印迹结果显示,在白色、灰色和黑色皮肤均有STX17蛋白阳性条带且灰色皮肤中表达量最高,黑色皮肤次之,白色皮肤中表达量是最低的,这与荧光定量检测结果一致,体外培养的小鼠黑色素细胞中也有STX17蛋白阳性条带.实验结果表明,小鼠Stx17基因在皮肤组织、毛囊角化细胞以及黑色素细胞中均有表达,Stx17可能参与毛色的形成,且在小鼠腹部毛色变浅中起到了一定的作用.     

The influence of long-term chromatic adaptation on pigment cells and striped pigment patterns in the skin of the zebrafish, Danio rerio

The striped pigment patterns in the flanks of zebrafish result from chromatophores deep within the dermis or hypodermis, while superficial melanophores associated with dermal scales add a dark tint to the dorsal coloration. The responses of these chromatophores were compared during the long-term adaptation of zebrafish to a white or a black background. In superficial skin, melanophores, xanthophores, and two types of iridophores are distributed in a gradient along the dorso-ventral axis independent of the hypodermal pigment patterns. Within one week the superficial melanophores and iridophores changed their density and/or areas of distribution, which adopted the dorsal skin color and the hue of the flank to the background, but did not affect the striped pattern. The increases or decreases in superficial melanophores are thought to be caused by apoptosis or by differentiation, respectively. When the adaptation period was prolonged for more than several months, the striped color pattern was also affected by changes in the width of the black stripes. Some black stripes disappeared and interstripe areas were emphasized with a yellow color within one year on a white background. Such long-term alteration in the pigment pattern was caused by a decrease in the distribution of melanophores and a concomitant increase in xanthophores in the hypodermis. These results indicate that morphological responses of superficial chromatophores contribute to the effective and rapid background adaptation of dorsal skin and while prolonged adaptation also affects hypodermal chromatophores in the flank to alter the striped pigment patterns.     

Simple method for quantification of fast plasma membrane movements.

We present a method for the quantification of the fast plasma membrane movements that are involved in ruffling, blebbing, fast shape change, and fast translocation. The method is based on the Kontron Vidas image analysis computer program. Video images from cells viewed through an inverted microscope were transmitted to the computer. The procedure was as follows: 4 consecutive video images were averaged (image 1); 28 s later a second set of 4 video images was averaged (image 2); image 2 was subtracted from image 1 and the grey level of each pixel of the resulting image was increased with 128 grey level units, resulting in the subtraction image, showing a uniform grey background speckled with brighter and darker spots corresponding to areas of movement. These spots were discriminated and turned into white objects against a black background. Interactive editing was used to delete artefacts that resulted from floating debris. The total area of the discriminated objects was measured, and the parameter motile area in micron2 per cell was calculated. We have applied our method to the study of motility induced in epithelial cell lines by the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate and by epidermal growth factor.     

Cyclical training enhances the melanophore responses of zebrafish to background colours

Zebrafish respond to visual stimuli to adapt their body colour to the background. If, rather than being a simple on/off reaction to visual stimulation, the colour change involves cognitive and memory-related processes, training fish with cyclical changes of the background would be expected to increase its ability to change colour. To test this, we developed a standardized procedure for quantifying the responses of melanophores to background changes in living adult specimens of leopard, a zebrafish mutant with spotted stripes. After training with 2-day cyclical alternation of white and black backgrounds for over 20 days, the proportion of the melanosome-filled area of dorsal melanophores, which was 20% on the black background before the training, increased up to 97%. In these trained fish, a rapid melanosome aggregation occurred within 10 s of the background change from black to white. The results indicate that the zebrafish melanophore responses can be modulated by learning, in which areal and speed control of melanosome movement are important for dispersion and aggregation, respectively.     

Variation in the Level of Grain Defect Light Flecks and Spots on Cattle Hides

The occurrence of hide damage light flecks and spots was determined on tanned hides from 28 herds during a period of 8 to 12 months. Light flecks and spots are described as small areas of grain loss up to 3 mm in diameter that are seen on dyed crust cattle leather. Damage was found on 75.8% of all hides. The neck and shoulders were the anatomical region with the highest prevalence of damage. Sixty-eight per cent of all hides had light flecks and spots in this region. The forelimbs and dewlap were the anatomical region with the second highest occurrence with a prevalence of 39.1%. This distribution corresponded to the known distribution of lice in cattle. No significant differences were observed in age, sex, prevalence of lice in the herd assessed in March or infestations with different lice species. The frequency of light flecks and spots varied significantly during the year. The frequency was highest in the late winter and early spring, decreased significantly during the summer and was lowest in the autumn. This variation supported the importance of lice in the development of light flecks and spots and suggested a relatively long healing period for the damages induced by lice.     

基于计算机视觉的罗非鱼适应环境的体色变化研究

多数鱼类的体色会受应激条件、环境背景、健康状况、生长发育和社会地位等因素的影响而发生改变。本文利用基于计算机视觉的体色量化技术研究正常情况和社会应激条件下罗非鱼对背景颜色的适应性,以及在背景颜色变化过程中体色变化的响应速度。实验结果表明：已适应白色背景的鱼放入黑色背景水体后,体色变化主要发生在前10s内,放入时和放入10s后的体色明度值差异极显著（**p＜0.01）;在白色背景下适应的鱼放入黑色背景下适应2h后其体色变得很黑,将其放入白色背景水体后体色在10s内可发生由深到浅的变化,放入时和放入10s后的体色明度值差异极显著（** p＜0.01）。在蓝色背景下适应的鱼放入黑色背景水体后,体色变化主要发生在前10s内,放入时和放入10s后的体色明度值差异显著（*p＜0.05）。在蓝色背景下适应的鱼放入黑色背景下适应2h后的体色变得很黑,再将其放入白色背景水体后体色由深变浅,放入时和10s后的体色明度值发生极显著变化（**p＜0.01）。处于社会应激条件下劣势地位的鱼体色会变黑,刚放入白色背景水体时的平均灰级达到12.7阶,放入60s、1800s后的体色和刚放入时没有显著差异。受社会应激影响轻微的鱼体色在1800s后适应了环境的颜色,明度值和没有受应激影响鱼的体色接近,而受伤或受社会应激影响较严重的鱼体色改变较小。鱼在高浓度非离子氨（UIA浓度为0.178 mg/L）的水中处理3h后,鱼的体色变得很黑,刚放入白色背景水体时平均灰级达到15.1阶,放入10s、120s后鱼的体色变化不大,放入180s后鱼的体色变浅,平均灰级达到9.3阶,与刚放入时的体色明度相比差异显著（*p＜0.05）。     

Morphology of the Leather Defect Light Flecks and Spots

The skin histology and the scanning electron microscope morphology of the hide defect light flecks and spots after tanning were studied in 11 steers infested with biting lice (Damalinia bovis). Nine steers from herds free of lice were used as controls. Skin biopsies from 6 of the animals in the lice infested group showed mild to moderate hyperkeratosis and moderate perivascular to diffuse dermatitis with infiltration of mainly mononuclear cells and some eosinophilic granulocytes. The steers were slaughtered at an age of 18 to 23 months. Light flecks and spots occurred on all examined hides from the infested group after tanning. No examined hides from the control group demonstrated similar damage. Both light microscopic examination of sections of tanned hide with light flecks and spots and scanning electron microscopy of the same defects showed superficial grain loss and craters with a irregular fibre base encircled by smooth and intact grain.     

The production of chimeric rats and their use in the analysis of the hooded pigmentation pattern

New, improved media and procedures for making rat chimeric embryos and culturing them in vitro have been developed. We have produced 27 rat chimeras: 20 males and 7 females. This ratio of males to females is consistent with that seen in mouse chimeras, suggesting that rat sex chimeras develop as phenotypic males. By aggregating embryos containing appropriate genetic markers for pigment cell differentiation, it is possible to produce chimeras that elucidate the site of action of the hooded gene. The coat color patterns of black ? black hooded chimeras display a white belly spot. In black ? albino hooded chimeras, small patches of white hair appear on the head and a large white spot occurs on the belly. Black ? agouti hooded chimeras display both agouti and nonagouti pigmentation over the entire surface of the chimera. These animals are fully pigmented with no white spots. In black ? albino non-hooded chimeras, rather small irregular patches of black and white hairs are distributed throughout the pelage. Histological examination of sections of hair follicles obtained from the white areas in the head of black ? albino hooded chimeras revealed amelanotic melanocytes. On the other hand, hair bulbs from the white belly spots do not contain any such melanocytes. Thus the white hairs of the head are due to the presence of albino melanocytes, but the white hairs of the belly are due to the total absence of melanocytes. All these observations are consistent with the conclusion that the hooded gene acts within melanoblasts, probably to retard their migration from the neural crest and/or to prevent their entrance into the hair follicles of the white areas of hooded rats.     

The influence of darkness and visual contrast on oviposition by Anopheles gambiae in moist and dry substrates

Abstract.  The influence of substrate brightness (value), contrast and colour (hue) on oviposition is quantified under low night-light levels of 1.2 × 10⁻⁴ w m⁻² in choice-tests using caged Anopheles gambiae sensu stricto laboratory strains and/or gravid An. gambiae sensu lato from a natural population in Western Kenya. Egg output increases as darkness of the substrate increases against a white background. Black substrates elicit the most oviposition by both laboratory and house-collected mosquitoes, whereas white elicits the least. Contrast between patches of substrate and background also influences egg placement. In four-choice tests, a black ovipositional dish against a white floor receives many more eggs than does black–black, white–white, and white–black dish vs. floor combinations. In a similar test presenting four grey vs. black combinations of dish vs. floor, females respond similarly to grey vs. black dishes and deposit nearly as many eggs on the dry floors as on wet dishes. Illumination at 2.1 × 10⁻³ w m⁻², equivalent to late dusk and early dawn, improves discrimination between black dishes and grey floors. Under the experimental conditions, An. gambiae females respond almost equally to dishes of water placed over red, yellow, green, blue and purple paper disks matching the brightness and saturation values of their neutral (grey) counterparts. Thus, no evidence is found for wavelength discrimination on oviposition. It is concluded that visual contrast strongly influences the search patterns for prospective ovipositional sites whereas darkness of substrate and moisture are strong releasers of oviposition.     

The Repertoire of Plant Cells

Cryptic (camouflaged) prey often seek out backgrounds that match their coloration, and when at rest adopt an attitude that makes their crypsis most effective. We suggest a simple method for investigating the adaptive significance of such orientation. We used flat discs of pastry as the ‘prey’, either plain white or painted with a central black stripe, and wild garden birds as the predators. In the eight main experiments the backgrounds were white wooden boards painted with black parallel stripes of the same width as the stripes on the prey. In each experiment we presented equal numbers of two (of seven) ‘treatments’ of prey. The selection resulting from the combined predation by the birds confirmed the advantages of resting on a matching background and in the ‘correct’ orientation. We suggest that the technique can be developed further to explore the adaptive significance of background matching     

Re-examination of the roles of environmental factors in the control of body-color polyphenism in solitarious nymphs of the desert locust Schistocerca gregaria with special reference to substrate color and humidity

This study re-examines the effects of environmental factors including substrate color, humidity, food quality, light intensity and temperature on the green-brown polyphenism, black patterning and background body color of solitarious (isolated-reared) nymphs of Schistocerca gregaria. All individuals reared in yellow-green or yellow containers became green morphs, whereas those reared in white, ivory-colored, blue, grey, brown, zinc-colored and black containers produced brown morphs in similar proportions. The intensity of black patterns was negatively correlated with the brightness of the substrate color of the containers. Humidity, which previous studies claimed controls green-brown polyphenism in this species, exerted no significant influence on either the green-brown polyphenism or the black patterning. Food quality also had little effect on body color. High temperature tended to inhibit darkening. The background body color on the thorax was greatly influenced by the substrate color of rearing containers and a close correlation was found between these two variables, indicating that, in contrast to what has been suggested by others, this species exhibits homochromy to match the body color to the substrate color of its habitat. Similar responses were observed in another strain, although some quantitative differences occurred between the two strains examined. Based on these results, a new model explaining the control of body-color polyphenism in this locust is proposed and the ecological significance of black patterns in solitarious nymphs is discussed.     

Sexual selection for white tail spots in the barn swallow in relation to habitat choice by feather lice

Many bird species have white spots in their tails or wing feathers, and such characters have been hypothesized to be either reliable signals (handicaps) or amplifiers that facilitate the message of a signal. In barn swallows, Hirundo rustica, the size of the white spots in the tail feathers is sexually dimorphic and positively correlated with feather length. We tested whether such spots act as handicaps or amplifiers. These white spots affect sexual selection in barn swallows, as shown by an experiment in which we randomly subjected males to (1) a considerable reduction of the size of all the spots by the use of a black permanent marker pen, (2) a small reduction of the size of the spots, or (3) no reduction. There was a positive association between spot size and the number of offspring produced per season. The white tail spots were preferred by feather-eating Mallophaga as a feeding site: holes made by Mallophaga were more abundant in the white spots than expected by chance. A habitat choice experiment with Mallophaga on barn swallow tail feathers revealed that they preferred white spots over black parts of the tail feathers. We therefore expected long-tailed male barn swallows to have more Mallophaga than short-tailed males. However, the opposite relationship was observed, indicating that long-tailed males may reliably signal their quality by the presence of large white tail spots without parasite damage. Thus white tail spots in barn swallows appear to be a reliable signal of phenotypic quality. Copyright 1999 The Association for the Study of Animal Behaviour.     

Do melanin-based tail patterns predict individual quality and sex in Lesser Grey Shrikes Lanius minor ?

In many bird species, males display colourful, usually carotenoid or structurally based plumage ornaments. On the other hand, there are many bird species and entire avian genera that are achromatic, i.e. with predominantly white, grey and black plumage colours. Achromatic plumage is a typical feature in many shrikes for example. In this study, we examine the importance of an achromatic plumage pattern, namely, the black tail spots on the two outermost tail feathers (T6 and T5) of Lesser Grey Shrikes (LGS) for sex discrimination and as an indicator of individual quality. Our results suggest that the black tail patterns, especially spots on T5, are important for sex discrimination, but only in combination with other melanin-based or morphological features. The presence of black tail spots on T5 is also an indicator of male age. However, there is no indication that presence, size and asymmetry of these black spots are indicators of individual quality of both sexes in the terms of breeding performances.     

Unsuspected cryptic polymorphism in the polychromatic Midas cichlid.

The Midas cichlid ( Cichlasoma citrinellum ) of Nicaragua shows stable polychromatism in that a consistent, small proportion of the fish in nature lose their melanophores and thereby become gold-coloured. Before metamorphosis, all fish look alike. We asked whether the pre-transformed offspring of gold and normal morphs might differ in their morphological and physiological responses to white and to black backgrounds despite looking the same. More chromatophores developed in all juveniles exposed for two weeks to a black than to a white background. When moved from one background to the other, the fish adjusted to white faster than to black. Most importantly, genetically normal fish (N) colour-matched quicker than genetically gold fish (G) irrespective of the direction of change. Adjustment in G was also more variable, indicating poorer control. A parallel pattern was recorded photometrically in melanophores of excised scales: aggregation of pigment was faster than dispersion. And pigment in the melanophores of N aggregated and dispersed swifter than did those of G. Therefore, pre-metamorphosed juvenile G could be more vulnerable to predation than are juvenile N. This reveals a possible source of selection against the offspring of gold morphs before they become gold-coloured.