{{Short description|Fish scale covering}} [[File:Spotted Gar (Lepisosteus oculatus) (3149758934).jpg|thumb|250px|The glassy appearance of the scales of this spotted gar is due to ganoine.]] thumb|The mineral texture of alligator gar scales consists of bundles of cross-plied hydroxyapatite minerals oriented towards the scale's surface. '''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,<ref name="Zylberberg1997">{{Cite journal | last1 = Zylberberg | first1 = L. | last2 = Sire | first2 = J. -Y. | last3 = Nanci | first3 = A. | doi = 10.1002/(SICI)1097-0185(199709)249:1<86::AID-AR11>3.0.CO;2-X | title = Immunodetection of amelogenin-like proteins in the ganoine of experimentally regenerating scales of Calamoichthys calabaricus, a primitive actinopterygian fish | journal = The Anatomical Record | volume = 249 | issue = 1 | pages = 86–95 | year = 1997 | pmid = 9294653 | doi-access = free }}</ref> such as gars and bichirs, as well as lobe-finned coelacanths.<ref>{{Cite journal|last1=Sire|first1=Jean-Yves|last2=Donoghue|first2=Philip C. J.|last3=Vickaryous|first3=Matthews K.|title=Origin and evolution of the integumentary skeleton in non-tetrapod vertebrates|journal=Journal of Anatomy|language=en|volume=214|issue=4|pages=409–440|doi=10.1111/j.1469-7580.2009.01046.x|issn=0021-8782|pmc=2736117|pmid=19422423|year=2009}}</ref> It is composed of rod-like, pseudoprismatic apatite crystallites, with less than 5% of organic matter.<ref name="Bruet2008">{{Cite journal | last1 = Bruet | first1 = B. J. F. | last2 = Song | first2 = J. | last3 = Boyce | first3 = M. C. | last4 = Ortiz | first4 = C. | s2cid = 17288901 | title = Materials design principles of ancient fish armour | doi = 10.1038/nmat2231 | journal = Nature Materials | volume = 7 | issue = 9 | pages = 748–756 | year = 2008 | pmid = 18660814|bibcode = 2008NatMa...7..748B }}</ref> Existing fish groups featuring ganoin are bichirs and gars, but ganoin is also characteristic of several extinct taxa.<ref name="Richter1994">{{Cite journal | last1 = Richter | first1 = M. | title = A microstructural study of the ganoine tissue of selected lower vertebrates | doi = 10.1006/zjls.1995.0023 | journal = Zoological Journal of the Linnean Society | volume = 114 | issue = 2 | pages = 173–212 | year = 1995 }}</ref> 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''.<ref name="Richter1994"/> While often considered a synapomorphic character of ray-finned fishes, ganoine or ganoine-like tissues are also found on the extinct acanthodii.<ref name="Richter1994"/>
It has been suggested that ganoine is homologous to tooth enamel in vertebrates<ref name="Zylberberg1997"/> or even considered a type of enamel.<ref name="Bruet2008"/> Ganoine indeed contains amelogenin-like proteins<ref name="Zylberberg1997"/> and has a mineral content similar to that of tetrapod tooth enamel.<ref name="Ørvig1967">{{cite book|last=Ørvig|first=T.|title=Structural and Chemical Organization of Teeth|chapter= Phylogeny of tooth tissues: Evolution of some calcified tissues in early vertebrates.|year=1967|publisher=Academic Press|location=New York|pages=45–110}}</ref>
==References== {{reflist}}
{{diversity of fish}}
Category:Fish anatomy Category:Tissues (biology)