Types of Scales in Fishes

Types of Scales in Fishes

1. Types of Scales Types of Scales
in Fishesin Fishes

2. ScaleScale
•A A scalescale is a small rigid plate that is a small rigid plate that
grows out of an grows out of an  animal's skin to 's skin to
provide protection.provide protection.
•Generally classified as part of an Generally classified as part of an
organism's integumentary system. organism's integumentary system.

3. •The study of scales is The study of scales is
called called SquamatologySquamatology. .

4. Development & Development &
LocationLocation
•Produced in the mesoderm.Produced in the mesoderm.
•Located between the epidermis and the Located between the epidermis and the
underlying tissues. underlying tissues.
•Genes responsible for the development of Genes responsible for the development of
scales in fish are same that result in hair scales in fish are same that result in hair
and tooth development in mammals.and tooth development in mammals.
•They usually grow on a fish in They usually grow on a fish in
overlapping plates, with the free end overlapping plates, with the free end
of the scale pointed towards the tail.of the scale pointed towards the tail.

5. Functions of Functions of
ScalesScales
•Provide external protection to its body as scales Provide external protection to its body as scales
are tough & slippery.are tough & slippery.
•Help to protect a fish from scrapes, parasites Help to protect a fish from scrapes, parasites
and other external injuries. and other external injuries.
•Because they are all attached at only one Because they are all attached at only one
point, they provide flexibility so that the point, they provide flexibility so that the
scales can slide over each other as the scales can slide over each other as the
fish’s body bends while swimming. fish’s body bends while swimming.

6. Types of ScalesTypes of Scales
•There are four different types of fish There are four different types of fish
scales.scales.
1.1.Cosmoid scalesCosmoid scales
2.2.Ganoid scalesGanoid scales
3.3.Placoid scalesPlacoid scales
4.4.Leptoid scalesLeptoid scales
•Cycloid scales Cycloid scales
•Ctenoid scalesCtenoid scales

7. •The structure and configuration of scales The structure and configuration of scales
can be used to determine the species from can be used to determine the species from
which they came.which they came.
•The type of scale will affect the behavior of The type of scale will affect the behavior of
a fish:a fish:
•Larger, heavier scales providing more Larger, heavier scales providing more
protection but restricting movement .protection but restricting movement .
•Smaller, lighter scales offering more Smaller, lighter scales offering more
freedom of movement but less protection.freedom of movement but less protection.

8. 1.Placoid Scales1.Placoid Scales

9. •Also called denticles, are similar in structure Also called denticles, are similar in structure
to teeth. to teeth.
•Found on sharks, skates and rays.Found on sharks, skates and rays.

•Formed of a rectangular base plate that is Formed of a rectangular base plate that is
embedded within the skin of the fish.embedded within the skin of the fish.
•The interior of the scale is a pulp that receives The interior of the scale is a pulp that receives
blood from the fish's vascular system, while the blood from the fish's vascular system, while the
outside is made of an enamel-like substance outside is made of an enamel-like substance
called vitrodentine.called vitrodentine.

11. •Placoids have a sharp ridge down the Placoids have a sharp ridge down the
center of the scale made of center of the scale made of vitrodentinevitrodentine..
•The enamel ridge is called The enamel ridge is called
an an ectodermal capectodermal cap, and this is important , and this is important
because without this enamel cap the because without this enamel cap the
sharks could not feed. sharks could not feed.
•Placoids do not grow with the fish. As a Placoids do not grow with the fish. As a
shark gets larger it grows new scales to fill shark gets larger it grows new scales to fill
in the gaps between the scales.  in the gaps between the scales. 

12. 2. Cosmoid Scales2. Cosmoid Scales

13. •Very rare scale type, but no doubt common in Very rare scale type, but no doubt common in
extinct species extinct species CrossopterygiansCrossopterygians , is the , is the
cosmoid scale.  cosmoid scale. 
•Limited today to the primitive lobefins Limited today to the primitive lobefins
and lungfish. and lungfish.
•Cosmoid scales evolved from placoid scales Cosmoid scales evolved from placoid scales
fusing together. fusing together.
•This is because cosmoid scales have two base This is because cosmoid scales have two base
plates and similar external spines composed of plates and similar external spines composed of
vitrodentine.vitrodentine.

14. •Inner layer of the Inner layer of the
scale is made scale is made
of lamellar bone. of lamellar bone.
•On top of this lies a On top of this lies a
layer of spongy layer of spongy
or vascular bone and or vascular bone and
then a layer then a layer
of dentine-like of dentine-like
material material
called cosmine.called cosmine.
•These scales grow These scales grow
along with the fish.along with the fish.

15. 3. Ganoid Scales3. Ganoid Scales

16. •These can be found These can be found
on gars, bichirs and on gars, bichirs and
reed fishes. reed fishes.
•Rare among modern Rare among modern
fish.fish.
•They are flat, basal-They are flat, basal-
looking scales.looking scales.
•What’s unusual about What’s unusual about
these scales is that these scales is that
they do not overlap they do not overlap
but instead fit together but instead fit together
like pieces of a jigsaw like pieces of a jigsaw
puzzle. puzzle.

17. •They have a bony base layer similar to that of They have a bony base layer similar to that of
cosmoid scales. Indeed, ganoid scales are cosmoid scales. Indeed, ganoid scales are
modified cosmoid scales.modified cosmoid scales.
•However, they differ in that their outer layer is However, they differ in that their outer layer is
made of an inorganic bone salt called ganoine made of an inorganic bone salt called ganoine
and that they are diamond-shaped and and that they are diamond-shaped and
interconnected.interconnected.
•Between ganoid scales are peg-and-socket Between ganoid scales are peg-and-socket
joints that articulate.joints that articulate.

18. •They act like armor to form a nearly They act like armor to form a nearly
impenetrable barrier to predators.impenetrable barrier to predators.
•They also grow with the fish, not only They also grow with the fish, not only
in length, but in width and thickness in length, but in width and thickness
as well.as well.

19. 4. Leptoid scales4. Leptoid scales
•Found on higher-order bony fish. Found on higher-order bony fish.
•As they grow they add concentric layers. As they grow they add concentric layers. 
•The two types are often grouped The two types are often grouped
together simply as together simply as "bony-ridged""bony-ridged"
scales.scales.
•They come in two forms:They come in two forms:
1.1.Cycloid ScalesCycloid Scales
2.2.Ctenoid ScalesCtenoid Scales

20. Cycloid ScalesCycloid Scales

21. •Cycloid and ctenoid Cycloid and ctenoid
scales have different scales have different
shapes but the same shapes but the same
composition and composition and
positioning.positioning.
•The vast majority of The vast majority of
bony fish have cycloid, bony fish have cycloid,
or round scales.or round scales.
•These have a smooth These have a smooth
outer edge and are most outer edge and are most
common on fish with soft common on fish with soft
fin rays such fin rays such
as salmon and carp. as salmon and carp.

22. •These have two basic parts; These have two basic parts;
1.1.The inner solid structure made The inner solid structure made
out of bone. out of bone.
2.2.An outer collagen layer. An outer collagen layer.

23. •Scales are not Scales are not
shed as the fish shed as the fish
ages, but grow ages, but grow
with the animal.with the animal.
•The result of this, The result of this,
is that a fish can is that a fish can
be aged by be aged by
counting the counting the
growth rings.growth rings.

24. •Herring and other groups of bony fish Herring and other groups of bony fish
have large cycloid scales that fall off have large cycloid scales that fall off
very easily. Skin structures that are very easily. Skin structures that are
shed easily are known as shed easily are known as deciduous deciduous
scalesscales..

25. Ctenoid scalesCtenoid scales

26. •They have a toothed They have a toothed
outer edge (exposed outer edge (exposed
part), spiny or have part), spiny or have
comb-like ridges.comb-like ridges.
•Usually found on fish Usually found on fish
with spiny fin rays, with spiny fin rays,
such such
as as bassbass and  and crappiecrappie..
•These have tiny teeth-These have tiny teeth-
like protrusions called like protrusions called
ctenii, giving them a ctenii, giving them a
rougher texture.rougher texture.

27.   Scute ScaleScute Scale
•Another less common, type of scale is Another less common, type of scale is
the the scutescute, which is:, which is:
•An external shield-like bony plate, orAn external shield-like bony plate, or
•A modified, thickened scale that often A modified, thickened scale that often
is keeled or spiny.is keeled or spiny.

28. •Some fish, such as pinecone fish, are Some fish, such as pinecone fish, are
completely or partially covered in completely or partially covered in
scutes.scutes.

29. Scaleless FishScaleless Fish
•Some groups of fish lack scales Some groups of fish lack scales
completely, including gobies and toadfish. completely, including gobies and toadfish.
•Instead, these fish are covered in a Instead, these fish are covered in a
coating of slime which will protect the fish coating of slime which will protect the fish
from injury and ectoparasites. from injury and ectoparasites.
•The slime layer may serve the added The slime layer may serve the added
function of making them especially hard function of making them especially hard
for a predator to grab hold of.for a predator to grab hold of.

31. ReferencesReferences
•www.wikipedia.orgwww.wikipedia.org
•www.australianmuseum.netwww.australianmuseum.net
•www.newton.depwww.newton.dep
•www.ehow.comwww.ehow.com
•www.earthlife.netwww.earthlife.net
•web.mac.comweb.mac.com