Biology:Ganoine

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Short description: Fish scale covering
The glassy appearance of the scales of this spotted gar is due to ganoine.

File:Mineral texture of ganoine layers in the scales of an alligator gar..tif Ganoine or ganoin is a glassy, often multi-layered mineralized tissue that covers the scales, cranial bones and fin rays in some non-teleost ray-finned fishes,[1] such as gars and bichirs, as well as lobe-finned coelacanths.[2] It is composed of rod-like, pseudoprismatic apatite crystallites, with less than 5% of organic matter.[3] Existing fish groups featuring ganoin are bichirs and gars, but ganoin is also characteristic of several extinct taxa.[4] It is a characteristic component of ganoid scales.

Ganoine is an ancient feature of ray-finned fishes, being found for example on the scales of stem group actinopteryigian Cheirolepis.[4] While often considered a synapomorphic character of ray-finned fishes, ganoine or ganoine-like tissues are also found on the extinct acanthodii.[4]

It has been suggested that ganoine is homologous to tooth enamel in vertebrates[1] or even considered a type of enamel.[3] Ganoine indeed contains amelogenin-like proteins[1] and has a mineral content similar to that of tetrapod tooth enamel.[5]

References

  1. 1.0 1.1 1.2 Zylberberg, L.; Sire, J. -Y.; Nanci, A. (1997). "Immunodetection of amelogenin-like proteins in the ganoine of experimentally regenerating scales of Calamoichthys calabaricus, a primitive actinopterygian fish". The Anatomical Record 249 (1): 86–95. doi:10.1002/(SICI)1097-0185(199709)249:1<86::AID-AR11>3.0.CO;2-X. PMID 9294653. 
  2. Sire, Jean-Yves; Donoghue, Philip C. J.; Vickaryous, Matthews K. (2009). "Origin and evolution of the integumentary skeleton in non-tetrapod vertebrates" (in en). Journal of Anatomy 214 (4): 409–440. doi:10.1111/j.1469-7580.2009.01046.x. ISSN 0021-8782. PMID 19422423. 
  3. 3.0 3.1 Bruet, B. J. F.; Song, J.; Boyce, M. C.; Ortiz, C. (2008). "Materials design principles of ancient fish armour". Nature Materials 7 (9): 748–756. doi:10.1038/nmat2231. PMID 18660814. Bibcode2008NatMa...7..748B. 
  4. 4.0 4.1 4.2 Richter, M. (1995). "A microstructural study of the ganoine tissue of selected lower vertebrates". Zoological Journal of the Linnean Society 114 (2): 173–212. doi:10.1006/zjls.1995.0023. 
  5. Ørvig, T. (1967). "Phylogeny of tooth tissues: Evolution of some calcified tissues in early vertebrates.". Structural and Chemical Organization of Teeth. New York: Academic Press. pp. 45–110.