Observations on the pigmentation of the pigeon iris

There are three genetically controlled iris types found in the pigeon, two of which contain stromal pigment cells, the third lacks pigment cells. The yellow (gravel) and white (pearl) iris types have pigment cells that contain birefringent pigment granules (crystals) and are ultrastructurally similar to iridophores of poikilothermic vertebrates. Both these iris types contain guanine as a major "pigment" and, in addition, the yellow iris contains at least two yellow fluorescing pigments that are tentatively identified as pteridines. The pigment cells of the yellow and white irises are structurally identical differing only in the presence or absence of these yellow pigments. The stromal pigment cells of the white iris correspond in structure and pigment chemistry to classical iridophores although they lack strong irridescence and are therefore perhaps best considered leucophores. The pigment cells of the yellow iris can be considered "reflecting xanthophores" having the combined properties of both classical xanthophores and iridophore/leucophores.     

Two Genomic Loci Control Three Eye Colors in the Domestic Pigeon (Columba livia)

The iris of the eye shows striking color variation across vertebrate species, and may play important roles in crypsis and communication. The domestic pigeon (Columba livia) has three common iris colors, orange, pearl (white), and bull (dark brown), segregating in a single species, thereby providing a unique opportunity to identify the genetic basis of iris coloration. We used comparative genomics and genetic mapping in laboratory crosses to identify two candidate genes that control variation in iris color in domestic pigeons. We identified a nonsense mutation in the solute carrier SLC2A11B that is shared among all pigeons with pearl eye color, and a locus associated with bull eye color that includes EDNRB2, a gene involved in neural crest migration and pigment development. However, bull eye is likely controlled by a heterogeneous collection of alleles across pigeon breeds. We also found that the EDNRB2 region is associated with regionalized plumage depigmentation (piebalding). Our study identifies two candidate genes for eye colors variation, and establishes a genetic link between iris and plumage color, two traits that vary widely in the evolution of birds and other vertebrates.     

The fine structure of photoreceptors in a marine flatworm

Summary The ocelli or eyes of the marine polyclad turbellarian Notoplana acticola are clustered on the paired dorsal nuchal tentacles and in two longitudinal bands lateral to the cerebral ganglion. The ocelli, studied by electron microscopy, were characterized as rhabdomeric and non-ciliary in origin. There are 60 to 80 ocelli per animal each enclosed in a fibrous capsule to which muscle fibers may attach. An ocellus consists of a pigmented eyecup into which 30 to 50 photoreceptor cells send dendritic processes through interruptions in or among pigment cell projections across the eyecup opening. The dendritic processes terminate in numerous long intertwined microvilli which fill the eyecup. The nucleated cell body of each photoreceptor cell lies outside the eyecup and projects an axonal process to the cerebral mass. Within the dendritic processes are observed mitochondria, ribosomes, neurotubules, multivesicular bodies, vesicles and vacuoles. The cell body contains smaller mitochondria, endoplasmic reticulum, ribosomes, vesicles and prominent Golgi complexes.After dark adaptation, there are some structural alterations in terms of swelling of microvilli, increased numbers of vacuoles associated with the microvilli and dendritic processes, and changes in the pigment cell projections.This work was supported by Grant No. GM 10292 from the U.S. Public Health Service to Professor Richard M. Eakin, Department of Zoology at the University of California, Berkeley, U.S.A., where this investigation was conducted during the author's sabbatical leave of absence from the University of Illinois, and by Grant No. 1 SO 1 FR 5369 from the U.S. Public Health Service to the University of Illinois at the Medical Center.I express appreciation to Professor Eakin for interesting discussions and generous hospitality to me as a guest in his laboratory, and to the John Simon Guggenheim Memorial Foundation for the Fellowship which I held during 1964–65. I thank Dr. John P. Marbarger, Director of the Aeromedical Laboratory for the electron microscope facilities used at the University of Illinois.     

Absorption microphotometry of irregular-shaped objects

Summary A new microphotometric method (mainly for the evaluation of microchemical color reactions) which uses measurements at two wave lengths (developed byOrnstein and, independently, by the author) is presented in a form which greatly reduces the computational labor (for an illustration, see Table 3).Contribution from the Program in Cytology, Department of Botany, University of Wisconsin, Madison, supported in part by grants to Dr.C. Leonard huskins from the Research Committee of the Graduate School with funds supplied by the Wisconsin Alumni Research Foundation.     

Characterization of the Reflective Materials and Organelles in the Bright Irides of North American Blackbirds (Icterinae)

The reflective materials in the iris stroma of bright-irised American blackbirds (Icterinae, Emberizidae) and the red-eyed vireo (Vireo olivaceus) (Vireonidae) were characterized using high-performance liquid chromatography (HPLC) and diode-array detection. Two purines, guanine and hypoxanthine, and two pteridines, leucopterin and xanthopterin, were detected in large amounts in all bright irides. The brown iris of the red-winged blackbird (Agelaius phoeniceus) by comparison contained only small amounts of these and additional unidentified compounds. The absolute and relative amounts of light-absorbing compounds in the iris varied somewhat among species of blackbirds with bright irides, and markedly within one species (brewer's blackbird, Euphagus cyanocephalus) between sexes and age classes that vary in eye color. Differences in the types, numbers, and sizes of pigment organelles in the irides appeared to underlie the differences in amounts of light-absorbing compounds. Guanine was the most abundant light-absorbing compound in all bright irides, accounting for about 90% of the total absorption at 250 nm. A wide range of concentrations of guanine, from 96 to 9 μg per iris, produced bright irides. The primary pigment organelles of pigment cells in bright irides were reflecting platelets, which typically appeared as open spaces on electron micrographs. In the red-eyed vireo there were in addition red pterinosome-like pigment organelles in the pigment cells on the anterior surface of the iris stroma. Guanine was present even in irides with no overt reflecting platelets.     

Trichophyton rubrum (Castellani) var. flava,var. nova a yellow pigment forming Trichophyton rubrum

Summary and Conclusions A hitherto unknown variant ofT. rubrum var.flava is described which besides its yellow pigment has the following characteristics different fromT. rubrum (Castellani). A much slower growth and a smaller diameter of the giant culture and an appreciable difference in the light absorption curve of the extracted pigment.     

Plant color effects of certain anomalous forms of theRrallele in maize

Summary The genetically changes forms ofR ^r arising regularly in maize plants heterozygous for the stippled, light stippled, and marbled alleles, and previously shown to influence aleurone color differentially, were found to affect coleoptile and seedling leaf sheath color also. Failure to demonstrate corresponding differential effects on root pigmentation possibly was due to inadequacy of the testing procedure. Two of the modified forms ofR ^r were observed to reduce glume and anther color also. The experimental results imply that theR locus as a region is involved in the phenomenon.Paper No. 677 from the Department of Genetics, College of Agriculture, University of Wisconsin.     

An evaluation of certain indices of eutrophy and maturity in lakes

Summary Data from five Colorado lakes were utilized to test the usefulness of net primary productivity, seston, chlorophyll a and Secchi disc transparency as indices of eutrophy. The four indices were in essential agreement as to the relative degree of eutrophication in each of the five lakes. The concept of maturity is also considered by ranking the Colorado lakes according to several maturity indices: phytoplankton diversity, zooplankton diversity, Margalef's pigment ratio, P/B ratio, and assimilation number. The relative maturity of the lakes shifts considerably, according to which maturity index one utilizes. Specific correlations between maturity indices (e.g., a positive correlation between plankton diversity and pigment ratio) as suggested by Margalef, did not occur in these five lakes. The data from the Colorado lakes suggest that maturity may not be a meaningful concept or, that if it is, it has not been adequately characterized.Contribution No. 55, Limnology Laboratory, University of Colorado, Boulder. This research was supported, in part, by Penrose Fund Grant No. 5284 from the American Philosophical Society and by NSF Grant GY 5306.     

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.     

Specific substrates for isolation and differentiation of Azotobacter vinelandii

Summary Resorcinol, ethylene glycol and glutaric acid have been found to be specific substrates for the enrichment of Azotobacter vinelandii in the presence of other Azotobacter species. The three compounds may also be used for species differentiation in the genus Azotobacter. In contrast to other reports strains of A. chroococcum and A. beijerinckii have been isolated which are able to use L-rhamnose for growth.Conditions for the production of a yellow pigment and green fluorescence by A. vinelandii from non-aromatic substrates on agar-plates have been tested.The production of water soluble yellow pigments in benzoate containing media cannot be used as a criterium for the presence of A. vinelandii. The pigment seems to be -hydroxy-muconic semialdehyde, the splitting product resulting from metacleavage of catechol. It may be formed by all Azotobacter species that can metabolize aromatic substrates.     

Comparison of Two Pearl Sacs Formed in the Same Recipient Oyster with Different Genetic Background Involved in Yellow Pigmentation in <Emphasis Type="Italic">Pinctada fucata</Emphasis>

Color is one of the most important factors determining the commercial value of pearls. Pinctada fucata is a well-known pearl oyster producing high-quality Akoya pearls. Phenotypic variation in amount of yellow pigmentation produces white and yellowish pearls. It has been reported that polymorphism of yellow pigmentation of Akoya pearls is genetically regulated, but the responsible gene(s) has remained unknown. Here, we prepared pearl sac pairs formed in the same recipient oyster but coming from donor oysters that differ in their color. These two pearl sacs produced pearls with different yellowness even in the same recipient oyster. Yellow tone of produced pearls was consistent with shell nacre color of donor oysters from which mantle grafts were prepared, indicating that donor oysters strongly contribute to the yellow coloration of Akoya pearls. We also conducted comparative RNA-seq analysis and retrieved several candidate genes involved in the pearl coloration. Whole gene expression patterns of pair sacs were not grouped by pearl color they produced, but grouped by recipient oysters in which they were grown, suggesting that the number of genes involved in the yellow coloration is quite small, and that recipient oyster affects gene expression of the majority of genes in the pearl sac.     

On the heredity of Y-linked color genes in Xiphophorus pygmaeus nigrensis Rosen (Pisces)

Summary The inheritance of two Y-linked colour genes of the Poecillid Xiphophorus pygmaeus nigrensis has been described. Males with the gene Fl (=flavus) posess a yellow colouration of the body whereas those with the gene Vfl (= venter flavus) only at the basis of the anal ray. These patterns depend on G-xanthophores, yellow pigment cells with colourless granulation (Öktay).Cross-breedings with X. maculatus and X. milleri cause an intensification of the patterns by increase of the number of the G-xanthophores and their transformation into xanthoerythrophores (colour cells with red granulation). Backcross males with X. maculatus inheriting Fl or Vfl show a red colouration of the whole body.These results may be explained by the theory of Kosswig, Gordon and Öktay of polygenic modifier systems. Their function is to regulate the number, the intensity and the grade of pigment cells, while the colour gene activates this process of establishing the pattern and determines the center of it. Modifiers in X. pygmaeus nigrensis changing G-xanthophores into xanthoerythrophores are below a genetic level or absent.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

Comparative studies on the nature and distribution of pigments from two thermophilic bacteria

Summary The pigments of two strains of extremely thermo-resistant bacteria were extracted and examined spectrophotometrically. Both strains contain -carotene as the main pigment according to the spectral characteristics of the pigment in various solvents. According to quantitative data Thermus aquaticus contains more than one hundred times as much of the pigment than is found in strain YT-G, representing almost 80% of the total lipid. The carotene of strain YT-G is destroyed by hot saponification, while that of T. aquaticus resists that procedure without alterations. T. aquaticus contains a small amount of a second pigment with absorption maxima at 370, 400 and 420 m.Solubilization of the membrane of spheroplasts derived from acetate-C¹⁴-labelled cells of T. aquaticus, followed by separation of the crude membrane fraction, showed that about 50% of the C¹⁴ is associated with the membrane fraction. More than 90% of the C¹⁴ is recovered in the yellow supernatant of the acetone-extracted crude membrane fraction, showing that a rapid incorporation of the label into the pigment occurs. The assumption that the pigment is associated with the membrane is supported by submicroscopical observations: T. aquaticus has a well-defined cytoplasmic membrane, and on top of this a sandwiched layer, which is embedded in a very electron-dense material, that we assume to consist of the pigment. Strain YT-G which contains only minute quantities of the same pigment, does not possess this kind of an outer membrane, but shows only a cytoplasmic membrane envelopped by the cell wall.The main experiments were done while on leave to the Ames Research Center, as a recipient of a Senior Post-doctoral Resident Research Associateship of the National Research Council, Washington, D.C., from the Dept. of Exobiology, University of Nijmegen, Driehuizerweg 200, Nijmegen, The Netherlands.     

Variability in the production of amylase by three isolates ofMyrothecium roridum

Amylase production by three isolates ofMyrothecium roridum under different cultural conditions was studied. Starch followed by dextrin induced maximum amylase production (dextrinizing and saccharifying) by all the three isolates. Glucose was a poor substrate for the production of amylases. Bitter gourd isolate was a comparatively more efficient producer of amylases than the other two isolates. Addition of glucose to the starch medium resulted in a repression of amylases. Urea was a good source of nitrogen for induction of dextrinizing amylase in bitter gourd and pearl millet isolates.l-Asparagine,l-tyrosine were good sources of nitrogen for induction of saccharifying amylase in bitter gourd, water melon and pearl millet isolate, respectively. With a few exceptions, dextrinizing amylase production was inhibited by gibberellic acid, cycocel, calcium chloride and calcium sulfate, while these substances stimulated saccharifying-amylase production. No correlation could be observed between amylase production and vegetative growth. Amylases of all the three isolates ofM. roridum were characterized.     

Mapping and validation of a major QTL for yellow pigment content on 7AL in durum wheat (<Emphasis Type="Italic">Triticum turgidum</Emphasis> L. ssp. <Emphasis Type="Italic">durum</Emphasis>)

Yellow pigment content in durum wheat (Triticum turgidum L. ssp. durum) is an important criterion for both pasta bright yellow color and human health because of antioxidant properties of carotenoids involved in this pigmentation. In the present study, QTLs for yellow pigment content in durum wheat were mapped in a population of 140 RILs developed from a intraspecific cross between a released variety (PDW 233) and a landrace (Bhalegaon 4). This trait was evaluated in one location for 3 years and in two more locations for one additional year (five different year × location combinations further called “environments”). Yellow pigment content was highly heritable across the five different environments. Analysis of variance showed the significant effect of genotype, environment and genotype × environment interaction on the trait. Five different QTLs linked to yellow pigment content were identified on chromosome 1A, 3B, 5B, 7A and 7B across five different environments. The strongest one located on the distal part of the long arm of chromosome 7A, QYp.macs-7A, explained 55.22% of the variation in the trait, while, remaining four QTLs explained 5–8.75% of phenotypic variation in yellow pigment content. Marker analysis revealed significant association of one ISSR and one AFLP fragment with the trait. These two markers were linked to the major QTL QYp.macs-7A and were converted into SCAR markers. These SCAR markers were further validated on another population as well as 38 diverse genotypes so as to prove their potential in marker assisted selection. These markers will be very useful for the marker assisted breeding of durum wheat for higher yellow pigment content.     

CONVERGENT EVOLUTION OF RED CAROTENOID COLORATION IN WIDOWBIRDS AND BISHOPS (EUPLECTES SPP.)

Avian carotenoid‐based signals are classic examples of sexually selected, condition‐dependent threat displays or mate choice cues. In many species, male dominance or mating success is associated with redder (i.e., longer wavelength) color hues, suggesting that red colors are either more efficient or more reliable signals than yellow colors. Few studies, however, have investigated selection for redness in a macroevolutionary context. Here, we phylogenetically reconstruct the evolution of carotenoid coloration in the African widowbirds and bishops (Euplectes spp.), for which agonistic selection for redder hues, as well as pigmentary mechanisms, is well documented. Using reflectance spectrometry for objective color quantification, and accounting for phylogenetic uncertainty, we find that yellow plumage color is a retained ancestral state in Euplectes, and that red color hues have convergently evolved two or three times. Results are discussed in relation to a known diversity in pigment mechanisms, supporting independent origins of red color, and suggesting that agonistic selection and physiological constraints have interacted to generate color diversity in Euplectes.     

Ein Mechanismus zur Steuerung des Lichtflusses in den Rhabdomeren des Komplexauges von Musca

Summary In the ommatidia of Musca, the light flux transmitted by each one of the rhabdomeres of sense cells no. 1 to 6 decreases as a function of time if light falls onto these rhabdomeres. With a similar time course the light flux reflected from these rhabdomeres increases. These changes take place within a few seconds following illumination. The results have been established in the intact animal using changes in the appearance of the pseudopupil as indicator and also in surviving preparations of the eye with direct inspection of the rhabdomeres.The changes are interpreted as a consequence of interactions between pigment granules in the sense cells and electromagnetic fields induced outside the rhabdomeres by light travelling on the inside: In the dark adapted situation the granules are quite distant from the rhabdomeres, the interaction is negligible. During light adaptation the granules move close to the rhabdomeres, and as a consequence, total reflection of the light in the rhabdomere is frustrated. The relatively rapid changes in the optical characteristics of the rhabdomeres are explained by the fact that the distance, the granules have to move in order to switch from one condition to the other is in principle on the order of the wavelength of light.The results indicate, that the changes in the position of the granules are induced by the excitation of the respective sense cells themselves, for instance by the degree of their depolarisation. No interaction between the sense cells of one ommatidium nor between those of different ommatidia could be found.The function of the movement of the pigment granules is interpreted as a means to protect the sense cells no. 1 to 6 against strong illumination. — Movement of pigment granules is not induced in sense cells no. 7 and 8 with light intensities which give maximal response in sense cells no. 1 to 6.

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Wertvolle Diskussionen verdanken wir Herrn Dr. K. G. Götz sowie Herrn Prof. W. Reichardt. Wir danken Fräulein T. Wiegand für Mithilfe bei den Experimenten sowie Herrn E. Freiberg für das Fertigstellen der Abbildungen.     

不同叶色三叶海棠叶片成色色素分析

结合民族植物学和药理学的研究方法,对西双版纳地区傣族、哈尼族和基诺族等3个少数民族民间利用番石榴（Psidium guajava）、余甘子（Phyllanthus emblica）和水柳（Homonoia riparia）的传统知识进行调查研究及体外抗菌活性实验。结果表明：番石榴和余甘子在村寨中较为常见,当地少数民族将其种植于庭院中,常作为果蔬食用,食用番石榴嫩叶可缓解拉肚子的症状,治疗腹痛、腹泻。水柳生长在水边,傣族会将其叶作为腌酸鱼的配料之一。根据文献记载,番石榴、余甘子和水柳的叶部位作为药使用时,常煎水外洗,治疗皮肤瘙痒。对这3种药用植物叶部位采用80%乙醇浸泡制备的提取物进行体外抗菌实验,结果显示番石榴、余甘子和水柳3种药用植物对金黄色葡萄球菌和大肠埃希菌均有较好的抑菌和杀菌活性,其最小抑菌浓度MIC在98~390 μg·mL 1之间,最小杀菌浓度MBC在98~781 μg·mL 1之间。番石榴和水柳叶对铜绿假单胞菌有一定抑菌和杀菌活性,其MIC和MBC范围均为6 250~12 500 μg·mL 1。由此可见,这3种药用植物的民间利用具有一定的合理性和药用开发价值。     

A study of melanin in a truly monohybrid black mouse

Summary In the monohybrid black mouse used for this experiment melanin granules are distributed in the hair, the epidermis, the corium, the pia mater, the parathyroid and the pigment layer of the retina, the choroid, the iris and the ciliary body of the eye. Sometimes they are found in the phagocytes of the spleen and the lymph nodes. The color gene, C, determines the presence of melanin in the tissues mentioned above. In the albino mice of the same inbred strain the absence of the color gene causes the absence of melanin. No other differences between the tissues of the black and albino mice were observed. The melanin first appears in the optic cup of the embryo when 12 days old. At birth it appears in the hairs; later in the other organs. This article contains the substance of a thesis which formed a part of the requirements for the degree of Master of Science in the Graduate Yuan of Natural Sciences in Yenching University, Peiping, China. The work has been done in the Department of Anatomy of the Peiping Union Medical College under a fellowship granted by the same institution.