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）。     

Genetic determinants of sable and umbrous coat color phenotypes in mice

The dorsal fur in yellow F1 mice (F1-Ay) between C3H/HeJ and C57BL/6J-Ay is darker than that in C57BL/6J-Ay. Moreover, yellow F2 mice (F2-Ay) exhibit a wide spectrum of coat color phenotypes in terms of lightness and darkness. Quantitative trait locus (QTL) analysis on F2-Ay identified three significant modifier loci that accounted for darkening of the coat color on chromosomes 1 (Dmyaq1 and Dmyaq2) and 15 (Dmyaq3), and the C3H/HeJ allele at these loci increased the darkness. Because agouti F2 mice (F2-A) also exhibited a spectrum of coat color phenotypes, the question of whether these QTLs had any effects on F2-A was examined. Dmyaq1 and Dmyaq2 were shown to increase the darkness in F2-A, whereas Dmyaq3 did not. The results showed that Dmyaq1-Dmyaq3 were parts of determinants responsible for the sable (darker modification of yellow) coat color phenotype, and that Dmyaq1 and Dmyaq2 were parts of determinants responsible for the umbrous (darker modification of agouti) coat color phenotype. It is, thus, demonstrated that both the sable and the umbrous phenotypes resulted from multigenic contributions, and that they shared genetic bases, as had been implied for several decades.     

Fifty shades of brown: Macroevolution of plumage brightness in the Furnariida,a large clade of drab Neotropical passerines

Both natural and sexual selection are thought to affect the evolution of bird color. Most studies of the topic have focused on sexually dichromatic taxa and showy plumages, which are expected to be more influenced by social selection and usually result in increased conspicuousness. However, many bird clades display dull brown or gray plumages that vary greatly in brightness (lightness), but little in hue (shade). Here, we examine the macroevolution of brightness in one such clade, the Furnariida. We make comparisons across light environments, body parts, monochromatic lineages, and each sex of dichromatic lineages. We found that support for models including light environments is greater for the dorsum than for the venter, and that brightness evolution is more constrained in the former than in the latter. Plumages in this clade have evolved to be darker in darker habitats, consistent with natural selection for increased crypsis. Finally, the features of brightness macroevolution are broadly similar across the sexes of the dichromatic clade, challenging the view that sexual dichromatism is driven by different evolutionary processes acting in each sex. We conclude that, in the Furnariida, light environments and dorsal–ventral variation are more important than sex as axes of color evolution.     

Recessive yellow in the Mongolian gerbil (Meriones unguiculatus)

A new autosomal recessive coat color mutant in the Mongolian gerbil (Meriones unguiculatus) is described: recessive yellow. On the dorsal side the mutant has a rich yellow to ginger color. Ventrally it shows the typical creamy white belly of a wild-type Mongolian gerbil. The dorsal yellow hairs have short black tips, and a light olive green base. A clear demarcation line between dorsal and ventral color is present. Crosses between recessive yellow animals and multiple homozygous recessive tester animals (a/a; c^chm/c^chm; g/g; p/p) resulted only in animals of an agouti (wild-type) phenotype, showing that the new allele is not allelic with any of the known coat color mutations in the Mongolian gerbil. Molecular studies showed that the new mutant is caused by a missence mutation at the extension (E) locus. On a non-agouti background (a/a; e/e) mutant animals look like a dark wild-type agouti. In contrast to wild-type agouti it shows yellow pigmentation and dark ticking at the ventral side, resulting in the absence of a demarcation line. Since black pigment is present in both the agouti and non-agouti variant (A/A; e/e and a/a; e/e), we conclude that recessive yellow in the Mongolian gerbil is non-epistatic to agouti. Additionally we describe a second mutation at the same locus leading to a similar phenotype, however without black pigment and diminishing yellow pigment during life. Fertility and viability of both new mutants are within normal range. The extension (E) gene is known to encode the melanocortin 1 receptor (MC1R). Interestingly, this is the only gene that is known to account for substantial variation in skin and hair color in humans. Many different mutations are known of which some are associated with higher skin cancer incidence.     

Adaptation of Pelage Color and Pigment Variations in Israeli Subterranean Blind Mole Rats,Spalax Ehrenbergi

Background

Concealing coloration in rodents is well established. However, only a few studies examined how soil color, pelage color, hair-melanin content, and genetics (i.e., the causal chain) synergize to configure it. This study investigates the causal chain of dorsal coloration in Israeli subterranean blind mole rats, Spalax ehrenbergi.

Methods

We examined pelage coloration of 128 adult animals from 11 populations belonging to four species of Spalax ehrenbergi superspecies (Spalax galili, Spalax golani, Spalax carmeli, and Spalax judaei) and the corresponding coloration of soil samples from the collection sites using a digital colorimeter. Additionally, we quantified hair-melanin contents of 67 animals using HPLC and sequenced the MC1R gene in 68 individuals from all four mole rat species.

Results

Due to high variability of soil colors, the correlation between soil and pelage color coordinates was weak and significant only between soil hue and pelage lightness. Multiple stepwise forward regression revealed that soil lightness was significantly associated with all pelage color variables. Pelage color lightness among the four species increased with the higher southward aridity in accordance to Gloger''s rule (darker in humid habitats and lighter in arid habitats). Darker and lighter pelage colors are associated with darker basalt and terra rossa, and lighter rendzina soils, respectively. Despite soil lightness varying significantly, pelage lightness and eumelanin converged among populations living in similar soil types. Partial sequencing of the MC1R gene identified three allelic variants, two of which were predominant in northern species (S. galili and S. golani), and the third was exclusive to southern species (S. carmeli and S. judaei), which might have caused the differences found in pheomelanin/eumelanin ratio.

Conclusion/Significance

Darker dorsal pelage in darker basalt and terra rossa soils in the north and lighter pelage in rendzina and loess soils in the south reflect the combined results of crypsis and thermoregulatory function following Gloger''s rule.     

Camouflage versus running performance as strategies against predation in a lizard inhabiting different habitats

Running speed and camouflage are associated with the foraging and anti‐predator abilities of animals. The toad‐headed lizard, Phrynocephalus versicolor, has evolved a darker dorsal color in melanistic habitats and maintained a lighter color in adjacent, non‐melanistic habitats. We test the hypothesis that lizards have weaker running speed on well‐matching backgrounds than on less matching backgrounds. We used lizard models to compare the predation pressure, while the running speed of dark and light lizards were compared in field tunnels using a video recording method. Our results indicated that both the dark lizards in melanistic Heishankou (HSK) and the light lizards in non‐melanistic Guazhou (GZ) face lower predation pressure than potential color‐background unmatched lizards. The light lizards have a potentially higher running speed than darker lizards in melanistic habitats, which implies that substrate color matching populations with benefits of camouflage might have lower anti‐predation pressure, and the costs of investment in melanin production may reduce running capacity.     

赤腹松鼠一新亚种

在查对中国南部赤腹松鼠标本(401号)的基础上,发现分布于云南东北部昭通地区的赤腹松鼠与赤腹松鼠其他亚种有明显的区别.毛色特征:背部棕黄色,背中央区域稍带黑色;腹部至前胸栗红色;喉、颏部棕灰色;尾毛背腹无明显差异,尾毛末端棕黄、次末端黑,尾末端具棕黄色(稍黄白)区域;前后足背棕褐色,稍带黑色.进一步对头骨可量性状数据进行分析(差异系数),结果表明:分布于该地区的赤腹松鼠分别与赤腹松鼠其他13个亚种两两之间至少有一项差异系数大于1.28,系一新亚种Callosciurus erythraeus zhaotongensis subsp.nov..     

Variation of the melanocortin 1 receptor gene in the macaques

Melanocortin 1 receptor (MC1R), a G-coupled seven-transmembrane receptor protein, plays a key role in the regulation of melanin synthesis in mammals. Sequence variation of the MC1R gene (MC1R) has been associated with pigmentation phenotypes in humans and in several animal species. The macaques (genus Macaca) are known to show a marked inter-specific variation in coat color although the causative genetic variation remains unclear. We investigated nucleotide sequences of the MC1R in 67 individuals of 18 macaque species with different coat color phenotypes including black and agouti. Twenty-eight amino acid replacements were identified in the macaques, but none of these amino acid replacements could explain the black coat color of Macaca silenus and the Sulawesi macaque species. Our molecular evolutionary analysis has revealed that nonsynonymous substitution/synonymous substitution (dN/dS) ratio of the MC1R has not been uniform in the macaque groups and, moreover, their coat color and dN/dS ratio were not related. These results suggest that the MC1R is unlikely to be responsible for the coat color variation of the macaques and functions of MC1R other than pigmentation might be associated with the different selective pressures on the MC1R in macaques.     

Pigment cell differentiation in the fire-bellied toad,Bombina orientalis. I. Structural,chemical, and physical aspects of the adult pigment pattern

Wild-collected adults of Bombina orientalis are bright green dorsally and red to red-orange ventrally. As a prelude to an analysis of the differentiation of pigment cells in developing B. orientalis, we describe structural and chemical aspects of the fully differentiated pigment pattern of the “normal” adult. Structurally, differences between dorsal green and ventral red skin are summarized as follows: (1) Dorsal green skin contains a “typical” dermal chromatophore unit comprised of melanophores, iridophores, and xanthophores. Red skin contains predominantly carotenoid-containing xanthophores (erythrophores), and skin from black spot areas contains only melanophores. (2) In ventral red skin, there is also a thin layer of deep-lying iridophores that presumably are not involved in the observed color pattern. (3) Xanthophores of red and green skin are morphologically distinguishable from each other. Dorsal skin xanthophores contain both pterinosomes and carotenoid vesicles; ventral skin xanthophores contain only carotenoid vesicles. Carotenoid vesicles in dorsal xanthophores are much larger but less electron dense than comparable structures in ventral xanthophores. The presence of carotenes in ventral skin accounts for the bright red-orange color of the belly of this frog. Similar pigments are also present in green skin, but in smaller quantities and in conjunction with both colored (yellow) and colorless pteridines. From spectral data obtained for xanthophore pigments and structural data obtained from the size and arrangement of reflecting platelets in the iridophore layer, we attempt to explain the phenomenon of observed green color in B. orientalis.     

The genetics of adaptive coat color in gophers: coding variation at Mc1r is not responsible for dorsal color differences

The genetics of adaptation is a key problem in evolutionary biology. Pocket gophers of the species Thomomys bottae provide one of the most striking examples of coat color variation in mammals. Dorsal pelage color is strongly correlated with soil color across the range of the species, presumably reflecting the selective pressure exerted by predation. To investigate the genetic basis of coat color variation in T. bottae, we cloned and sequenced the melanocortin-1 receptor locus (Mc1r), a candidate pigmentation gene, in 5 dark and 5 light populations of the species. Our results show that, in contrast to many other species of mammals and other vertebrates, coding variation at Mc1r is not the main determinant of coat color variation in T. bottae. These results demonstrate that similar phenotypic variation may have a different genetic basis among different mammalian species.     

Effects of substrate color on intraspecific body color variation in the toad‐headed lizard,Phrynocephalus versicolor

Diversity in animal coloration is generally associated with adaptation to their living habitats, ranging from territorial display and sexual selection to predation or predation avoidance, and thermoregulation. However, the mechanism underlying color variation in toad‐headed Phrynocephalus lizards remains poorly understood. In this study, we investigated the population color variation of Phrynocephalus versicolor. We found that lizards distributed in dark substrate have darker dorsal coloration (melanic lizards) than populations living in light substrates. This characteristic may improve their camouflage effectiveness. A reciprocal substrate translocation experiment was conducted to clarify the potential role of morphological adaptation and physiological plasticity of this variation. Spectrometry technology and digital photography were used to quantify the color variation of the above‐mentioned melanic and nonmelanic P. versicolor populations and their native substrate. Additionally, substrate color preference in both populations was investigated with choice experiments. Our results indicate that the melanic and nonmelanic populations with remarkable habitat color difference were significantly different on measured reflectance, luminance, and RGB values. Twenty‐four hours, 30 days, and 60 days of substrate translocation treatment had little effects on dorsal color change. We also found that melanic lizards choose to live in dark substrate, while nonmelanic lizards have no preference for substrate color. In conclusion, our results support that the dorsal coloration of P. versicolor, associated with substrate color, is likely a morphological adaptation rather than phenotypic plasticity.     

Coat color determination by miR-137 mediated down-regulation of microphthalmia-associated transcription factor in a mouse model

Coat color is a key economic trait in wool-producing species. Color development and pigmentation are controlled by complex mechanisms in animals. Here, we report the first production of an altered coat color by overexpression of miR-137 in transgenic mice. Transgenic mice overexpressing miR-137 developed a range of coat color changes from dark black to light color. Molecular analyses of the transgenic mice showed decreased expression of the major target gene termed MITF and its downstream genes, including TYR, TYRP1, and TYRP2. We also showed that melanogenesis altered by miR-137 is distinct from that affected by UV radiation in transgenic mice. Our study provides the first mouse model for the study of coat color controlled by miRNAs in animals and may have important applications in wool production.     

Switching of melanocyte pigmentation associated with pituitary pars intermedia tumors in Rb+/- and p27-/- female mice with yellow pelage

As an incidental finding in a study of mammary tumorigenesis, two lines of genetically engineered mice were observed to develop pigmentation changes of the fur. Mice with targeted mutations of the Rb1 (Rb) and Cdkn1b (p27kip1) genes were crossed from C57BL/6 (black coat color; eumelanin) and 129Sv (wild-type agouti coat color) backgrounds, respectively, to one with a dominant yellow coat color (phaeomelanin) carrying a transgene for Agouti under a keratinocyte specific promoter. Both Rb+/- and p27-/- mice developed pituitary tumors of the pars intermedia that were associated with a switch to black (eumelanic) fur but were not observed in sibling Rb+/+ and p27+/+ mice. This phenomenon was observed first in the vibrissae and, subsequently one to two weeks later, as periorbital and dorsal patches, and was associated with pituitary lesions larger than four millimeters in the longest dimension. In Rb+/- mice, pigmentation change preceded a moribund state attributable to the tumors by two to four weeks, whereas in p27-/- mice, the pigmentation alteration was earlier, more gradual, and prolonged. The switch from phaeomelanin to eumelanin in the fur is most likely due to out-competition of the agouti gene product by alpha-melanocyte-stimulating hormone from the pituitary tumors, an effect masked in black or agouti mice.     

THE SELECTIVE ADVANTAGE OF CRYPSIS IN MICE

The light color of mice that inhabit the sandy dunes of Florida's coast have served as a textbook example of adaptation for nearly a century, despite the fact that the selective advantage of crypsis has never been directly tested or quantified in nature. Using plasticine mouse models of light and dark color, we demonstrate a strong selective advantage for mice that match their local background substrate. Further our data suggest that stabilizing selection maintains color matching within a single habitat, as models that are both lighter and darker than their local environment are selected against. These results provide empirical evidence in support of the hypothesis that visual hunting predators shape color patterning in Peromyscus mice and suggest a mechanism by which selection drives the pronounced color variation among populations.     

Ultrastructural variation tune wing coloration of a moth Asota caricae Fabricius, 1775

Butterflies and moths develop highly ordered coloration in their wing for signal transmission. We have investigated the ultrastructural arrangement of wing coloration of a moth Asota caricae, applying light, optical polarized, and scanning electron microscopy, and spectrophotometry. The forewing of the moth is brown in color with a white spot at the center. The hindwing is golden yellow in color with many black patches in it. The ventral part of the forewing and dorsal hindwing share the similar color pattern. The ventral part of the hindwing has dull coloration in comparison to the dorsal one although the pattern remains same. The spectrometry analysis reveals various patterns of absorbance and reflectance spectra for various colors. The peak observed for various colors remain same although the intensity of peak changes. Bright colors possess highly ordered structures whereas irregular structures are found in dull colored scales. The color variation observed due to dorsal and ventral part of the wing is due to the minute difference observed in terms of ultrastructural arrangement revealed by scanning electron microscope. The color pattern of A. caricae is due to variation of microstructures present within the scale.     

Development of a novel pink-eyed dilution mouse model showing progressive darkening of the eyes and coat hair with aging

Oca2^p-cas (oculocutaneous albinism II; pink-eyed dilution castaneus) is a coat color mutant gene on mouse chromosome 7 that arose spontaneously in wild Mus musculus castaneus mice. Mice homozygous for Oca2^p-cas usually exhibit pink eyes and gray coat hair on the non-agouti genetic background, and this ordinary phenotype remains unchanged throughout life. During breeding of a mixed strain carrying this gene on the C57BL/6J background, we discovered a novel spontaneous mutation that causes darkening of the eyes and coat hair with aging. In this study, we developed a novel mouse model showing this unique phenotype. Gross observations revealed that the pink eyes and gray coat hair of the novel mutant young mice became progressively darker in color by approximately 3 months after birth. Light and transmission-electron microscopic observations revealed a marked increase in melanin pigmentation of coat hair shafts and choroid of the eye in the novel mice compared to that in the ordinary mice. Sequence analysis of Oca2^p-cas revealed a 4.1-kb deletion involving exons 15 and 16 of its wild-type gene. However, there was no sequence difference between the two types of mutant mice. Mating experiments suggested that the novel mutant phenotype was not inherited in a simple fashion, due to incomplete penetrance. The novel spontaneous mutant mouse is the first example of progressive hair darkening animals and is an essential animal model for understanding of the regulation mechanisms of melanin biosynthesis with aging.     

Contrasting Mode of Evolution at a Coat Color Locus in Wild and Domestic Pigs

Despite having only begun ~10,000 years ago, the process of domestication has resulted in a degree of phenotypic variation within individual species normally associated with much deeper evolutionary time scales. Though many variable traits found in domestic animals are the result of relatively recent human-mediated selection, uncertainty remains as to whether the modern ubiquity of long-standing variable traits such as coat color results from selection or drift, and whether the underlying alleles were present in the wild ancestor or appeared after domestication began. Here, through an investigation of sequence diversity at the porcine melanocortin receptor 1 (MC1R) locus, we provide evidence that wild and domestic pig (Sus scrofa) haplotypes from China and Europe are the result of strikingly different selection pressures, and that coat color variation is the result of intentional selection for alleles that appeared after the advent of domestication. Asian and European wild boar (evolutionarily distinct subspecies) differed only by synonymous substitutions, demonstrating that camouflage coat color is maintained by purifying selection. In domestic pigs, however, each of nine unique mutations altered the amino acid sequence thus generating coat color diversity. Most domestic MC1R alleles differed by more than one mutation from the wild-type, implying a long history of strong positive selection for coat color variants, during which time humans have cherry-picked rare mutations that would be quickly eliminated in wild contexts. This pattern demonstrates that coat color phenotypes result from direct human selection and not via a simple relaxation of natural selective pressures.     

褐色种皮大豆与其黄色种皮衍生亲本的表型及基因型比较

大豆种皮色在从野生大豆到栽培大豆的选择过程中逐渐由黑色变成黄色,是重要的形态标记,因此,大豆种皮色相关基因的研究无论是对进化理论研究还是育种实践都具有非常重要的意义。利用褐色种皮J1265-2大豆及其衍生亲本黄色种皮大豆J1265-1为材料,通过SSR引物扩增片段,检验遗传背景的异同,同时对控制种皮的候选基因GmF3’H进行扩增和测序分析。结果表明,褐色种皮和黄色种皮材料不仅用161对SSR分子标记检测没有发现差异,其褐色种皮候选基因GmF3’H的编码区及起始密码子上游1465 bp序列也是一致的。因此,证明褐色种皮J1265-2大豆与其衍生亲本黄色种皮大豆J1265-1为近等基因系,其控制褐色种皮的基因型与已报道的基因型不同。     

Darker where cold and wet: Australian birds follow their own version of Gloger's rule

Gloger's rule is usually interpreted as predicting darker coloured animals in warmer and more humid/vegetated regions. The relative importance of temperature and rainfall or vegetation is however unclear, and often only one variable is tested at a time, mainly through proxies. Here, I assess the predictions of Gloger's rule for interspecific achromatic plumage variation (dark to light variation) for an entire avifauna (551 species of Australian landbirds). I tested the effects of climatic variables (temperature and rainfall) and vegetation structure on plumage reflectance at species and assemblage level (100 × 100 km cells), controlling for phylogenetic relatedness and spatial autocorrelation. To assess the robustness of these results I compared observed results with those of a null distribution of effects obtained from repeatedly simulating random plumage reflectance evolution on the phylogeny. At both the species and assemblage level, darker coloured birds were found in wetter and colder regions and in more densely vegetated habitats. Simulations confirm results at the species level and the effect of temperature at the assemblage level, but rainfall and vegetation effects at the assemblage level fall within the distribution of simulated effects and should be interpreted with care. Interspecific colour variation in Australian birds supports Gloger's rule for rainfall/vegetation, but shows the opposite pattern for temperature. Darker colours in wet and vegetated environments are consistent with the role of melanin pigmentation in preventing feather degradation by bacteria, but also with background‐matching for camouflage. Darker plumage might be beneficial in colder regions or detrimental in warmer regions if it affects thermoregulation, a selective force often only assumed to be of importance for ectotherms. The data highlight the need to test the generality of biogeographic rules across levels and at broad scale. Experimental work is needed to confirm the mechanisms linking plumage achromatic variation to climate.     

Geographic variation for colour in the sandburrowing beetle Chaerodes trachyscelides White (Goleoptera: Tenebrionidae) on New Zealand beaches analysed using CIELAB L * values

Chaerodes trachyscelides White is a highly specialized, flightless burrowing beetle confined to the narrow strip of sand at and just above high water level on sandy marine beaches in New Zealand. Although the ventral surface of the beetle is always pale, the dorsal surface varies from pale to almost black. Large samples of this beetle were taken, together with the sand, from 11 beaches on New Zealand's three main islands. The colour of the dorsal surface of each individual beetle and that of the sand samples was measured using reflectance spectroscopy and expressed as CIE L*,a*,b* (CIELAB) values. The L* values, which are objective, quantitative measures of the degree of lightness of the beetles, were subjected to statistical and frequency analysis. Although the species was very variable in colour and the variation appeared to be continuous, a highly significant correlation was obtained between the mean of the L* values for the samples on each beach and that of the sand, the correlation coefficient being 0.961. This close association between the lightness of the beetles and that of the sand suggests the variable melanism functions as cryptic colouration. On most beaches, the distribution oflightness among the beetles sampled conformed to a normal curve. For beetles from sites where the sand was relatively uniform, such as the black Taranaki beaches, the L* frequency distribution curves were narrow and the coefficient of variation of mean beetle colour was relatively small indicating low colour variability. In contrast, the greatest within-site variability occurred on the two Stewart Island beaches sampled, where in each case there was less uniformity in the colour of the sand. At one of these sites, Maori Beach, darker sand present below the high water level is often deposited on the zone occupied by the beetles after storms. On Lonneker's Beach, the distribution of L* values among the beetles sampled was actually bimodal. On this small beach, there was an area of intensely black sand in the zone occupied by the beetles, but most of the rest was covered with light golden sand. These results are interpreted as evidence that the variability of colour of Chaerodes beetles has the effect of populations being able to match the colour of the sand of their home beaches, presumably as a consequence of the differential survival of individuals.