Pigment and colour change in fishes

1. PIGMENT AND COLOUR CHANGE IN
FISHES
Balwant Singh
M.Sc. (AAS)

2. Pigment And Colour Change In Fish es
• Colourations in fishes is due to the
presence of various kinds of pigments in
the integument several species are
brightly coloured exhibiting beautiful
characteristic patter white other have a
uniform shade .
• Some of the beautifully colour fish water
fishes species are the Carassious (gold fish
)Colisa ,Botia and Noemachelus.

3. • The bright colour are seen In the live or
freshly killed fishes .
• Colour in fish is due to presence of
Chromatophore and iridocytes.
• The chromatophore and orodocytes are
present in the integument above and below
the scales .
• Their number various in different species and
in different part of deferent species and in
deferent part of the body of the same species .

4. CHROMATOPHORES
• The chromatophore are branched cell lying
in the dermis and they are called
Erythrophores (red /orange) Xanthophore
(yellow) or Melanophores (Black) and
contain various type as pigment such as
Carotenoid (Yellow ,Red)
Melanin(Black),Purine (white or silvery) ,
Flavins (yellow) .
• Other colour like the blue ,green and brown are
due to the mixing of three kinds of
chromatophore in various proportion .

5. • The yellow red and orangs pigment are taken
throught the food while the black pigment are the
result of breckdown the amino acid (tyrosine)
• Usually chromatophore are large in number an
the ventral side
• The relative number of chromatophores ,kind of
pigment presint in them and the body result on a
variety of colour pattern seen in the fish spieces

6. • In the sword tail,Xiphophoorus helleri, the
beautiful colouration is due to the presence
of Xanthoerythrophores ,which contanin
yellow pigment in the process of the cell .
• The red pigment granules consist of an
outer limiting membrane and inner lamellae
•

7. IRIDOCYTES
• The iridocytes is specialized cells which are
also called “Mirror cell” due to the reffecting
great power possessed by them .
• The iridocytes contain guanine which is
white apaque or crystalline material and
occur in the form of crystals ,granules,
platelets .
• The iridocyte give white or silvery colour to
the body .

8. CHANGE IN COLOUR IN FISHES
• Several species of fishes can change their colour
so as adjust it to the surrounding.
• A temporary change in colour is effected by
rearrangment of pigment granules , but a semi
permanent change colour slowly by an increase
or decrease in the total number of
chromatophores.
• The when a fish moves to a darker environment
and has to stay there for some time , a slow
change in colour taken place.
• Generally change in colour of the fish is due to

9. • Cecentration of the pigment towards the centres
of the cells or their dispersion towards the
peryphery.
• The time reqired to bring about the
concerntration or dispersion of pigment , varies
in different (in thire habitat other factors )Species
• Sometime individual of a species deffer widelly
in their colour due o defferent in their habitat
• Other factor such as age, sex ,health ,and
emotion also influence the colour of a fish .

10. MECHANISM OF COLOUR CHANGE
• Migration of pigments in the chromatophore to
bring about change in colour is coordinated by
two methodes .
• Through hormones and through nerves
• Some species make use of only one of these
mechanism , while other depend on both .
• Its has been suggested the agrrregation and
dispersion of related to gelation (solidification of
liwuide )and solation (changing from a liqued to
get of the protoplasm in the cell .

11. • Other have suggested that contraction and
relation of the fibrils present between the outer
and inner membranes are respensible for the
movement of granules.
• Study on oryzia latipes , seem to indiate a
change in electric pontential as the mechanism to
couse movement of pigment granules .

12. NEURAL CONTROL
• The chromatophore in several species are
supplied with nerves ,and a neurenes
produced chemichal messenger called
neurohumors to active them .
• It is belived that ther are two kind of nerves fibre
having apposite effects .
• Neurohumors secret by one kinds of fiber cause
pigment dispersion ,while the other bring about
their cencentration .

13. • It has been observed that cutting of nerves
supplied to a particular area influencing the
chromatophores of that area .
• In Phoxinus phoxinus, nerves stimulation bring
about aggregation of melanin , and melanin
dispersing nerve fibers is also present in this
species .
• Neural control a bring about a rapid change in
the colour .
• But controle through harmones is relative as
slow process .

14. HORMONAL CONTROL
• In several species of fish , migration of pigment
granules in chromatophore in under the control
of pitutary gland .
• It has been observed the colour of the fishes
becomes light aggrigation of the pigment after
hypophysectomy (removel of pitutary gland ).
• Colouration of such a fish is restored temorarily .
• It pitutary extract is injected into the body .

15. • However some species do not respond to
hypophygosectomy or pitutary injection, suggesting
that their melanophore are not under the control of
harmone or more than one kinds of hormones are
needed to elicit response in them .
• It is well known that the melanophore stimulating
hormone (M.S.H) or intermedian is secreted by the
pors intermedia of the hypophysis .
• M.S.H bring about dispersion so the pigment in
melanohormone causing the skin to become darker .

16. • Its absentce resultes in the lighter shade ,due to
aggrigation of pigment .
• According to some authers a melanophore
concentration haris secreted in the hypothalamus
and a transported to pitutary for storage .
• It has also been suggusted that a melanophores
release harmone (M.S.H) and a melanophore
releaase inhabiting harmones (MRIH)may be
produced by the hypothalamus.

17. • Thus hypothalamus exercise control over the
secretion of MSH (inter media )from the pitutary
gland beside the above , adrenaline also
produced concetration sffect on pigment of
melanophores.
• Thyroxine produced by the thyroid gland is also
reportes influence the colour of the skin in some
species .
• In the Eel Anguilla anguilla , colour change in
under neural as well as harmonal control .
• When treted with adrenaline ,pigment
concentration has been abserved in the eels.

18. • Thus hormonal control ovarrides neural control .
• But fundulus neuralcontrol of melanophore is
stronger and dominantes over the hormonal
control .
• In shark and rays (condricthyes) , the response to
black and white background is affected by the
M.S.H ,and their appear to be little neural control
of melanophores .
• How ever pin eal play important role in colour
change in shark and rays.
• Fishes have been divided into three groups
depending upon the degree of neural control over
its melanophores.