Rapid Color Change Research Articles

Transitory colour changes in the new melanophores formed by quantitative colour change in the minnow Phoxinus phoxinus

Minnows (TeJeosiei: Phoxinus phoxinus (L.)) were exposed on a black background for varying periods to allow melanophore formation. The ages and times of appearance of melanophores were photographically determined. The background responses of the newly‐formed melanophores were assessed microscopically in fixed preparations of animals killed in liquid nitrogen at different time‐intervals. The results were interpreted according to the generally accepted belief that rapid and slow colour changes indicate nervous and hormonal mediation respectively. The age of the newly‐formed melanophores appeared to influence their background responses, the older melanophores being more responsive. It is suggested that the sensitivity to hormonal control develops first in the life of a pigment cell, to be followed later by sensitivity to nervous control. Nervous control, however, does not appear simultaneously for W/B and B/W adaptations but develops first for the latter. This differential development is considered to provide evidence for double innervation of melanophores.

Contrasts in Social Behavior between Central American Cichlid Fishes and Coral-reef Surgeon Fishes

The social systems and related behavior of cichlid and surgeon fishes are compared in terms of (i) physical spacing, (ii) theoretical spacing (communication), (iii) castes, (iv) group composition, (v) open versus closed groups, and (vi) reproductive behavior. Cichlids only recently invaded Central America. Despite the occurrence of about 100 species there, most are in one genus, Cichlasoma . Yet, they express a spectrum of feeding behavior, ranging from grazing herbivore through omnivore to predator, each of varying degrees of specialization. In contrast, their social behavior is remarkably conservative. There is a tendency for the generally found division of labor, with the female doing more of the direct caretaking of the eggs or fry and the male more of the defense, to lead toward polygyny. This is counterbalanced by the need for both parents to defend the fry. Communication is most accessible through a study of color patterns. While seemingly diverse, there is a common plan that entails the use of some or all of the same vertical bars and their central spots, and the appearance of yellow orange, red, or black ventrally. The coral-reef community is one of the oldest in existence. Surgeon fishes are pantropical, especially in the Pacific Ocean, and have developed distinct generic groupings within a compact family of about 75 species. Most are herbivorous, with some more specialized than others. The species fall into guilds, within which there is broad overlap in diets. The social systems differ radically, both when breeding and when not, and can be understood as consequences of their strategies of obtaining food. Wickler's classification of reproductive types within the Cichlidae is shown to be no advance over the previous dichotomy of substrate and mouthbreeding species. Poster coloration in surgeon fishes is apparently as important, or more, in extraspecific than intraspecific aggression, and poster-colored surgeon fishes show pronounced rapid color changes when fighting intraspecifically.

Microtubules, microfilaments, and pigment movement in the chromatophores of Palaemonetes vulgaris (Crustacea).

AbstractThe glass shrimp, Palaemonetes vulgaris changes to match the color of its background by a rapid, so‐called physiological color change and a much slower, morphological color change. Apparently both are controlled by hormones, but the rapid color change is mediated by translocations of pigments within stellate cells called chromatophores, whereas the slow color change is effected by selective increases in certain types of chromatophore pigments. The large, dark chromatophores of the ovary were isolated intact and shown to be polychromatic (perhaps four pigments) by correlating light and electron microscopy. Incubated chromatophores supplied with crude extracts of certain neurosecretory tissues exhibit centripetal movement of pigment equivalent to that observed in vivo when a prawn is transferred from a dark‐colored background to a light‐colored background. Centripetal translocation of pigment is not inhibited in the chromatophores by preincubation in 10−3 M colchicine or vinblastine sulfate even though the vinblastine treatment elicits production of crystalline complexes of microtubular protein in place of the normal bundles of microtubules. Cytochalasin B (10 μg/ml) blocks pigment migration reversibly, but does not disrupt microfilaments or other ultrastructural elements. Apparently, normal pigment aggregation depends on some function which is reversibly sensitive to cytochalasin B, and not on the impressive system of microtubules in these cells.

Dermatophyte Test Medium: Evaluation with Nondermatophytic Pathogens

The growth and color change produced on dermatophyte test medium (DTM) by 25 strains of zoopathogenic fungi associated with human skin lesions were evaluated quantitatively. DTM only partially suppressed the development of nondermatophytes, with total growth in most instances comparable with that observed with dermatophytes. Whereas all dermatophytes induced a rapid color change on DTM, several nondermatophytic pathogens induced an equally intense and almost as rapid conversion. The rapidity of this color change and the colonial morphology of these forms on DTM could cause their misidentification as dermatophytes under clinical conditions.

Countershading in the colourful reef fish Chaetodon lunula: Concealment, communication or both?

The widespread occurrence of countershading in coral reef fish seems to be evidence that the colours and patterns of these animals, however conspicuous they may appear to the human observer, are at least partially concerned with camouflage from predators. The alternative presented here, particularly relative to a butterfly fish Chaetodon lunula, is that countershading can be an adaptation to concealing a conspicuous signal. The conclusion is supported by the observation that this species eliminates its countershading by rapid colour change during intense intraspecific encounters. This colour change exposes highly conspicuous yellow areas. Colour change can thus make the signal dynamic. These signals may function to establish dominance relationships, especially between evenly matched individuals.

Phasic Color Changes in the Right Atrium of Dogs

SummaryHigh speed color motion pictures of the heart in 10 dogs have shown rapid phasic color changes in the right atrium which alternate between red and cyan with each cardiac cycle. Frame by frame measurement of color at 10 msec intervals throughout one cardiac cycle in one dog has shown a major red peak beginning approximately 195 msec after the onset of the P wave. Although the cause of these color changes is not yet known, they may result from phasic changes in coronary arterial flow through the atrial wall.

The dermal chromatophore unit.

Rapid color changes of amphibians are mediated by three types of dermal chromatophores, xanthophores, iridophores, and melanophores, which comprise a morphologically and physiologically distinct structure, the dermal chromatophore unit. Xanthophores, the outermost element, are located immediately below the basal lamella. Iridophores, containing light-reflecting organelles, are found just beneath the xanthophores. Under each iridophore is found a melanophore from which processes extend upward around the iridophore. Finger-like structures project from these processes and occupy fixed spaces between the xanthophores and iridophores. When a frog darkens, melanosomes move upward from the body of the melanophore to fill the fingers which then obscure the overlying iridophore. Rapid blanching is accomplished by the evacuation of melanosomes from these fingers. Pale coloration ranging from tan to green is provided by the overlying xanthophores and iridophores. Details of chromatophore structure are presented, and the nature of the intimate contact between the chromatophore types is discussed.

Experimental evidence for the regeneration of nerve fibres controlling colour changes after anterior spinal section in the minnow (Phoxinux PhoxinusL)

A method for quantitative recording of the general tint of the skin of the minnow is described. Using this method, the colour changes in response to black/white background reversal of normal and of equilibrated chromatically spinally operated minnows, previously black- or white-adapted for more than 9 months, were plotted to give standard curves. These enabled a clear distinction to be made between the rapid colour changes of the normal minnow with intact chromatic nervous system and the relatively very slow changes, only under hormonal control, of the chromatically spinally operated fish. Twenty minnows that had been white-adapted for more than 9 months and 19 that had been black-adapted for the same time were subjected to chromatic spinal section and replaced on the same backgrounds. At intervals their colour changes were recorded and plots of these records were compared with the standard curves. In the course of about 10 months 11 of these minnows showed a good recovery of rapid colour change, 9 showed medium recovery, 8 showed poor recovery and 11 continued to change colour at a rate typical of hormonal control. After another 9 months there was generally no further improvement. This varying degree of recovery of rapid colour change appears to have been the result of regeneration of chromatic fibres in the spinal cord, since a second section anterior to the level of the first and made 19 months after it was followed by darkening of the whole animal. Later it was able to change colour again in response to background reversal but these colour changes were of the slow hormonal type. Observations that recovery of nervously controlled colour change improved with time until some steady condition was reached and that there was great variation in this final degree of nervous control suggest that a number of chromatic fibres may run in the cord. Further,since the colour and pattern produced by the melanophores were affected equally over the whole body as the recovery of rapid colour change proceeded, it appears possible that each chromatic nerve fibre in the cord contributes to the state of excitation of a postganglionic system which is common to all the melanophores in the skin. Records of colour changes at certain stages during regeneration in the cord indicate that there was recovery of nervous control in one direction, i.e. for paling or darkening, while the change in the other direction was still only hormonal. Such observations suggest, in addition to the familiar concept of a nervous aggregating system, the existence of an active pigment-dispersing nervous mechanism.

Evaluation of the Color Changes of Screened Indicators: Phenol Red plus Methylene Blue and Phenol Red with Copper Oxalato Complex

The color change of phenol red when screened (optically filtered) by mixture with methylene blue is the same as the change of color of phenol red when screened with copper oxalato complex. An attempt has been made to differentiate the color changes of these two indicators with change of pH, by use of psychophysical data. The chromaticity coordinates of the colors of these indicators at different pH’s were determined. From these coordinates, the number of standard deviations of color matching, and consequently the color discrimination steps, were calculated on the basis of MacAdam ellipses. A new concept of Specific Color Discrimination, that is, the number of color discrimination steps per unit pH, has been introduced as a measure of visual sensitivity to indicator color change. It has been found that of the two screened indicators, phenol red plus methylene blue is the more sensitive; it shows a maximum Δc/ΔpH value of 11.8 in the range of pH 7.9–8.0. The second indicator, phenol red with copper oxalato complex, is almost as good; it has a maximum Δc/ΔpH. value of 8.6 at pH 7.2. The use of phenol red, alone, may give erroneous results, because it has two nearly equally sensitive Δc/ΔpH. peaks, at pH 7.4 and 8.4. The method is recommended for the quantitative evaluation of the pH of most rapid color change of other indicators, which until now has been only arbitrarily determined, visually.

カワハギおよびアミメハギの体色変化

A rapid and marked color change was observed on a filefish, Stephanolepis cirrhifer (TEMMINCK et SCHLEGEL) and four distinct patterns were recognizabl (Fig. 1). Among twelve fish which ranged from 7 to 9cm in length and were kept in a tank of 60 litres capacity in the laboratory, there appeared two dominants assuming the pattern B, whereas the other subordinates indicated no dark pattern (A). When these dominants were removed from the tank, two dominants newly appeared soon. The dominant actively drove subordinates away and fought with the other to occupy the food and space (c and d in Plate I). The excitement in these activities induced the remarkable dispersion of melanophores (C and D in Fig. 1). A rapid and extensive aggregation of melanophores resulting in the excitement pallor was also recognized when the fish were frightened violently. It is the most interesting fact that the time required for change of pattern is very short and the shift from one extreme to the other, for instance from D to A, occurs only in one or two seconds, and this may be the most rapid case so far known on fish (Table 1). Among the fish kept in a large aquarium in the Ueno Zoo, on the other hand, there was recognized no order and every fish assumed the pattern B or C, whereas the same rapid excitement pallor was observed. The behavior of the fish in the laboratory, therefore, must be a specific one induced by the experimental condition, perhaps by the dense keeping of fish. The similar color change due to excitement was also indicated by a different species of filefish, Rudarius ercodes (JORDAN et FOWLER) (Plate II).

Pattern Variability among Populations of the Gobiid Fish Bathygobius soporator

THE common shallow water goby, Bathygobius soporator (Cuvier and Valenciennes), is a widely distributed and variable species, found on Neotropical coasts and islands. A recent taxonomic review of the genus (Ginsburg, 1947) has presented evidence for the allocation of various populations to specific and subspecific ranks. Other species of this genus have been described from Pacific and African regions. Reports on the natural history of this fish have been limited to observations of Beebe (1931) and Breder (1943, 1948). Both authors have noted the remarkable color changing ability of Bathygobius, and the characteristic gill-like free pectoral fin rays, forming a fringe on the dorsal margins of these fins. Bathygobius soporator was found to be common in the tide pools and along sandy beaches in the vicinity of the Lerner Marine Laboratory, at Bimini Island, Bahamas. Because of rapid and extensive color and pattern changes, this species was considered a useful experimental animal in studies of mechanisms of pigmentary control in fishes. However, before any such studies could be attempted, an investigation of the normal variability in color and pattern was necessary. In the course of this investigation, certain population differences were found to be associated with different habitats. The present report, then, is a presentation of correlated observations on color changes, behavior, and ecology of Bathygobius soporator. The writer is indebted to the staff and facilities at the Lerner Marine Laboratory for making these investigations possible. Thanks are due to the director of the laboratory, Dr. Charles M. Breder, Jr., of the Department of Fishes and Aquatic Biology, American Museum of Natural History, for his comments and criticisms. The writer is also grateful to Dr. Lester R. Aronson, of the Department of Animal Behavior, American Museum of Natural History, for reading the manuscript and for his helpful suggestions.

The Source and Activity of Crago-Darkening Hormone (CDH)

T HE common shrimp, Crago, shows striking and rapid color changes in response to changes in background. The range of color change varies from very pale gray-white through darker grays to purple-black. At a slower rate Crago may also mimic the tint of any background other than a blue or green one (Koller, 1927). In addition to these changes, which occur uniformly over the whole body, there may be exhibited a mottled coloration of the body as a result of the production of darker and lighter areas. The telson and uropods may show their whole gamut of color change in a normal animal quite independently of the color of the remainder of the body, being sometimes very dark while the remainder of the body is light, or pale while the remainder of the body is dark; but usually these appendages tend to follow the color of the rest of the body. Although the color changes are usually adaptive, rendering the shrimp roughly the shade of the background upon which

Animal Concealment and Flash Coloration

MOMENTARY display by animals of conspicuous colours followed by reliance upon procrypsis has long been known. Jenner Weir (Trans. Ent. Soc. Lond., 22; 1869) directed attention to the conspicuous hind wings exhibited in flight by many otherwise cryptic moths and Oedipoda grasshoppers, and Lord Walsingham, in 1890 (Proc. Ent. Soc. Lond., 52; 1890), suggested that the sudden change when such flying insects came to rest serves to confuse the visual impressions of a pursuing enemy. H. B. Cott, in his work "Adaptive Coloration in Animals" (1940), devoted several pages and many figures to this 'flash coloration'. An interesting new example of the principle has been described in a letter from Staff-Sergeant J. E. Marson (6th (East Africa) Inf. Bde. Workshops, E.A.E.M.E., South-East Asia Command). "In Ceylon I have noted the effectiveness of the same principle as applied to certain species of spiders. The female of Herennia ornatissima (Doleschall) is a medium-sized spider, grey and brown above, with the underside of the abdomen and cephalothorax having brilliant yellow, orange or red markings, according to the maturity of the spider. It spins its web on rubber trees, from stumps of branches to the main trunk. The web is nine inches to a foot in length, and is very close to the trunk at all parts. The centre of the web is tubular and is fastened to the trunk by the tip of the tube. In this tubular depression, the female rests, almost perfectly camouflaged by the similarity of colour to the lichens which grow on the tree. If the spider is disturbed, however, a vivid red streak shoots down the trunk, as it jumps and lowers itself on a thread. The red streak stops as it alights further down the trunk with the underside of the abdomen covered. It is very difficult to follow the later part of this movement, owing to the rapid colour change. Many members of the Eresidœ, which retreat into their tube-like web endings when disturbed, jump when further attacked, and the same effect is produced by the highly coloured underside of the abdomen. It would appear that this colour change would once again offer protection against a foe attacking at close range."

The Pigmentary Effector System: a Review of the Physiology of Colour Response

AMONG the many unsolved problems of animal life., the significance of pigmentary colour and of rapid colour-change is one of the most elusive and attractive. Unlike the case of chlorophyll, the pigments of animals have no direct physiological value so far as really critical evidence goes at present. The colouring matters of birds' eggs, for example, the variable colouring of the egg of the guillemot, herring-gull, or cuckoo, has not yet been shown to possess the slightest relation to the welfare of the chick; nor has the (genuine) coloration or lack of colour in the skin or deeper tissues been proved conclusively to play a definite part in the welfare of the animal body. On the other hand, adaptational and survival value has been freely admitted, until recently, to account for the complex and exquisitely balanced correlation between coloration, habit, and environment in a large number of instances, of which insects and fishes offer the most notable examples. The difficulty that has made biologists sceptical of arguments that are used to prove protective, warning, and epigamic significance in animal colouring, lies in the absence of objective standards of excellence. How much does it benefit a flat-fish to fit so exactly into its niche and to stay there? How much does the note of warning avail? What was the value of the rough study in pigment before the painted animal canvas became amenable to the criticism of life? Are pigments or structural colours anything more than indices of chemical and physical structure, and is their biological value real or apparent only? The Pigmentary Effector System: a Review of the Physiology of Colour Response. By Dr. Lancelot T. Hogben. (Biological Monographs and Manuals.) Pp. xi + 152. (Edinburgh and London: Oliver and Boyd, 1924.) 10s. 6d. net.