Whiteling

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Whiteling is called a white individual from animals or plants of a species in which the individuals are usually different colors. In the past, the word albino was used with the same meaning ( synonymously ), today only disorders of the melanin structure are usually referred to as albinism.

Whites in plants

Completely white specimens of normally green plants are not able to survive on their own because they lack the green pigment chlorophyll , which enables photosynthesis to form organic substances such as saccharides that are required for survival . That is why the term white is also used for plants in which only the flowers are white, if the species in question normally has different colored flowers. Apart from the (green) chlorophylls there are other classes of colorants, the two most common are the (yellow-red) carotenoids and the (blue-red) anthocyanins . In the plant cells of flowers there are special organelles which, as plastids , unlike the green leaf bodies ( chloroplasts ), do not contain chlorophyll, but rather large amounts of carotenoids and are called chromoplasts because they carry the color of the flowers. In the course of flower formation, chloroplasts can transform into chromoplasts.

  • Orchis tridentata - normal flowers

  • Orchis tridentata - white flowers

  • White and normal red raspberry

  • Redwood branch with chlorophyll-free leaves

Somatic mutations - i.e. mutations that do not affect the germ cells in the flowers and seeds - can lead to individual branches of a bush having completely white leaves, which are also fed along with the root shoots.

If, for example, rice plants are formed (regenerated) from pollen or anthers , a considerable part of the resulting plants often lack chlorophyll. Plants do form proplastids , but part of their genes have been lost so that they cannot produce chlorophyll. Similar problems occur with wheat, but they can be reduced by special cultivation conditions.

Whites in mammals

In mammals, coat and skin color are caused by the composition and amount of melanins. Melanins are produced by melanocytes in specialized organelles called melanosomes. White bodies can arise through three different mechanisms.

  • As albinism , it is referred to as substances that are necessary for the synthesis of melanin, can not be made because of a mutation.
  • It is called leucism when, during development in the womb, the melanocytes do not migrate from the neural tube, from which the brain and spine later develop, to the organs where the melanocytes are supposed to produce their pigments.

There are also other reasons that lead to the emergence of white mammals. The mold is caused, for example, by a mutation of a gene that accelerates the division of melanocytes and causes them to die earlier and melanomas to occur relatively frequently at the same time.

Diseases in humans associated with melanin deficiency

  • Vitiligo, or white spot disease, manifests itself as white, pigment-free patches of skin that slowly become larger as the melanocytes die.
  • The Tuberous sclerosis or Bourneville-Pringle syndrome is an autosomal dominant inherited disease with an incidence of 1:20 000 to 1: 40,000 in the population. It shows up as adenoma sebaceum (many small, nodular tumors on the skin of the face and under the fingernails), epilepsy, increasing intellectual disability, and white spots on the skin. These spots are due to the fact that the melanosomes are created in the melanocytes but do not mature completely and therefore remain light.
  • Phenylketonuria is a hereditary metabolic disorder which, if left untreated, leads to severe mental retardation and also to light skin, hair and eyes.

Whites in birds

In addition to melanins, carotenoids and feather structures also play a role in the development of colors in birds . Carotenes are taken in through food. In birds, therefore, the causes of whites are albinism and leucism, as in mammals, and additionally the possibility that not enough carotenoids are available in the diet, that more carotenoids are consumed than usual, or that carotenoids are absorbed into the feathers is disturbed.

White flies in amphibians, fish and reptiles

In fish, amphibians and reptiles, the color of the skin and scales is caused by light interacting with three different types of chromatophores (pigment cells, dye- producing cells), the melanophores, xanthophores and iridophores.

Mutations are possible for each of these three dye-producing cell types, which correspond to leucism in that they change the direction and speed of the cells as they migrate from the neural tube to their destination. In the same way, mutations are possible for all types of dyes, which correspond to albinism insofar as they lead to the dye synthesis no longer being able to proceed properly. These types of whites are therefore also discussed under albinism and leucism .

Other reasons for the development of white mushrooms are malnutrition and changes in the control of dye synthesis. In the case of the flounder, feeding on one side results in some of the animals developing the same white color on the surface of the body as on the underside.

Individual evidence

  1. ^ Lincoln Taiz, Eduardo Zeiger: Physiology of plants. Heidelberg, Berlin: Spectrum Academic Publishing House. 2000, ISBN 3-8274-0537-8
  2. ↑ T. Harada, T. Sato, D. Asaka and I. Matsukawa: Large-scale deletions of rice plastid DNA in anther culture. Volume 81, Number 2, pp. 157-161 / February, 1991. doi : 10.1007 / BF00215717
  3. ^ W. Liu, MY Zheng, CF Konzaks: Improving green plant production via isolated microspore culture in bread wheat (Triticum aestivum L.). Plant Cell Reports Springer Berlin / Heidelberg Volume 20, Number 9, pp. 821-824 / February 2002 doi : 10.1007 / s00299-001-0408-x
  4. ↑ Gerli Rosengren Pielberg et al .: A cis-acting regulatory mutation causes premature hair graying and susceptibility to melanoma in the horse. In: Nature Genetics. 40, 1004-1009 (2008). doi : 10.1038 / ng.185 ; science.orf.at: Gene mutation turns the Lipizzaner horses into molds  ( page can no longer be accessed , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , accessed July 21, 2008.@1@ 2Template: Toter Link / science.orf.at  
  5. ↑ Hein van Grouw: Not every white bird is an albino: sense and nonsense about color aberrations in birds. (PDF; 458 kB)
  6. ^ H. Durrer and W. Villiger: Schiller radii of the gold cuckoo (Chrysococcyx cupreus (Shaw)) in the electron microscope. Cell and Tissue Research Volume 109, Number 3 / September, 1970 doi : 10.1007 / BF02226912
  7. ^ H. Durrer and W. Villiger: Schiller colors of the Trogonids Journal of Ornithology, Volume 107, Number 1 / January, 1966 doi : 10.1007 / BF01671870
  8. ↑ Matthew D. Shawkey and Geoffrey E. Hill: Significance of a basal layer melanin to production of non-iridescent structural plumage color: evidence from at amelanotic Steller's jay (Cyanocitta stelleri). The Journal of Experimental Biology 209, 1245-1250 doi : 10.1242 / jeb.02115 .
  9. ↑ Tony Gamble , Jodi L. Aherns, and Virginia Card: Tyrosinase Activity in the Skin of Three Strains of Albino Gecko (Eublepharis macularius). Gekko 5: pp. 39-44. (PDF; 767 kB)
  10. ↑ a b Jörg Odenthal, Karin Rossnagel, Pascal Haffter, Robert N. Kelsh, Elisabeth Vogelsang, Michael Brand, Fredericus JM van Eeden, Makoto Furutani-Seiki, Michael Granato, Matthias Hammerschmidt, Carl-Philipp Heisenberg, Yun-Jin Jiang, Donald A. Kane, Mary C. Mullins and Christiane Nüsslein-Volhard: Mutations affecting xanthophore pigmentation in the zebrafish, Danio rerio. Development, Vol 123, Issue 1 391-398, C 1996
  11. ↑ Frost-Mason SK, Mason KA: What insights into vertebrate pigmentation has the axolotl model system provided? Int J Dev Biol. 1996 Aug; 40 (4): 685-93. PMID 8877441
  12. ↑ Seikai, T .: Reduction in occurrence frequency of albinism in juvenile flounder Paralichthys olivaceus hatchery-reared on wild zooplankton. Bulletin of the Japanese Society of Scientific Fisheries (Japan) 1985 v. 51 (8) p. 1261-1267, ISSN  0021-5392 .