2. Structure of Skin of Fishes
•The Epidermis layer of skin in fishes:
•Epidermal glands:--The epithelium of
epidermis is modified into a variety of
glands, which are:
•(i) Mucous gland:
•(ii) Poison glands:
•(iii) Photophores:
•The Dermis layer of skin in fishes:-On
the basis of shape, scales are of four
types:
•(i) Plate like or placoid scales commonly
found in Elasmobranches.
•(ii) Cycloid scales found in Burbot and
soft-rayed fishes.
•(iii) Rhombic or diamond shaped scales,
common among gars and sturgeons.
• (iv) Ctenoid scales, characteristics of
spiny-rayed bony fishes
(Acanthopterygii).
3.
4. Dermis
• Underneath the epidermis Inner stratum spongiosm
Outer stratum compactum Collagen fibres .
• Fishes such as glass catfish, glass eel, the arrangement
of collagen fibres is extremely regular.
• Allowing light to pass through the dermis unreflect.
• In these fish the peritoneum is pigmented to protect
the abdominal organs from light Pigment cells.
• Dermis contains pigment cells that can occur in layers
at different levels.
• Pigment cells contain vareity of pigments other than
melanin Carotenoids Pterin Guanine crystals(silvery color)
Melanophores.
• Containing melanin absorbs the entire visible range of
light Astronotus ocellatus Melanophores (dark-brown)
are located in the dermis.
Xanthophores • Contains rhodopterin and carotenoid
granules and appear yellow to orange.
Iridophores • Cells that contain platelets of guanine or
hypoxanthine are called iridophores.
• These cells reflect light rather than absorb it giving fish
their shiney appearance.
