Conchiolin

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Conchiolin is an important component of mollusc shells (here almost exclusively mussels on the beach of the island of Cayo Costa on the Gulf coast of Florida)

Conchiolin (also Conchin , Conchyolin or Conchyn ) is the traditional name for the complex organic substance, in addition to calcium carbonate , the most important component of the shells of molluscs is (Mollusca). The name was coined in 1855 by the French chemist Edmond Frémy as part of a work on the chemical composition of various skeletal materials, in contrast to "ossein" ( collagen ), which he had isolated from bones .

Conchiolin is composed of fibroin -like scleroproteins , consisting mainly of the amino acids glycine , alanine and serine are constructed from various polysaccharides , notably chitin , as well as from aspartic acid -containing glycoproteins . These substances, like calcium carbonate, are deposited (secreted) from the mollusc's mantle (pallium).

The conchiolin is the main component of the "outer skin" ( periostracum ) of the mollusc shells and the matrix in which the calcium carbonate crystals of the inner layers of the shells are embedded (see →  mother-of-pearl ). This matrix - analogous to the collagen in the bones of vertebrates - gives the shells a certain elasticity and strength that far exceeds that of pure calcium carbonate. Depending on which proteins the conchiolin of the matrix is ​​made up of, the crystallization of aragonite or calcite is favored or inhibited.

Infection with pathogens in molluscs can cause abnormal deposition of pure conchiolin on the inside of the shell.

literature

  • Katharina Gries: Investigations into the formation processes and the structure of the mother-of-pearl of abalons. Dissertation, University of Bremen, 2011 ( PDF 25.4 MB).
  • Frederic Marin, Nathalie Le Roy, Benjamin Marie: The formation and mineralization of mollusk shell. In: Frontiers in Bioscience, Scholar Edition. Vol. 4, 2012, pp. 1099-1125, PMID 22202112 (alternative full text access : ResearchGate ).

Individual evidence

  1. ^ Ulrich Lehmann: Paleontological Dictionary. Enke, Stuttgart 1996, ISBN 3-432-83574-4 , p. 49.
  2. ↑ " Certaines espèces de coquilles, traitées par l'acide chlorhydrique, laissent un résidu d'une matière organique fort remarquable, d'un aspect brillant et feutré, insoluble dans l'eau, l'alcool et l'éther, et qui résiste à l'action des acides étendus j'ai donné à cette substance le nom de conchioline. [After treatment with hydrochloric acid, certain pots left a residue of a very remarkable organic material, light and felty in appearance, insoluble in water, alcohol and ether , and resistant to dilute acids, which I named conchiolin .] "Edmond Frémy: Recherches chimiques sur les os. In: Annales de chimie et de physique. Series 3, Vol. 43, 1855, pp. 47-107 ( Gallica ), p. 96
  3. ^ Conchin in the spectrum online lexicon of biology.
  4. ^ S. Huchette, C. Paillard, J. Clavier, R. Day: Shell disease: abnormal conchiolin deposit in the abalone Haliotis tuberculata. In: Diseases of aquatic organisms. Vol. 68, No. 3, 2006, pp. 267-271, doi : 10.3354 / dao068267 , PMID 16610593 .