Changes

The skin consists of [[Skin - Anatomy & Physiology#Epidermis|epidermal]] cells and '''scales''' (in most species) which are covered by a protective outer mucus '''cuticle'''.  Most fish are covered in a protective layer of slime (mucus).

The skin consists of [[Skin - Anatomy & Physiology#Epidermis|epidermal]] cells and '''scales''' (in most species) which are covered by a protective outer mucus '''cuticle'''.  Most fish are covered in a protective layer of slime (mucus).

[[image: Fish scales.jpg|thumb|250px|left|Scales of Bitterling (''Rhodeus amarus'')from the hindflank. The bluegreen colour of the tailstripe comes from the epidermis, background colour from the dermis.  Photograph by Piet Spaans]]

[[image: Fish scales.jpg|thumb|250px|right|Scales of Bitterling (''Rhodeus amarus'')from the hindflank. The bluegreen colour of the tailstripe comes from the epidermis, background colour from the dermis.  Photograph by Piet Spaans]]

There are four types of fish scales.

There are four types of fish scales.

# '''Cycloid scales''' are small oval-shaped scales with growth rings. Bowfin and remora have cycloid scales.

# '''Cycloid scales''' are small oval-shaped scales with growth rings. Bowfin and remora have cycloid scales.

# '''Ctenoid scales''' are similar to the cycloid scales, with growth rings.  They are distinguished by spines that cover one edge. Halibut have this type of scale.  

# '''Ctenoid scales''' are similar to the cycloid scales, with growth rings.  They are distinguished by spines that cover one edge. Halibut have this type of scale.  

Unlike mammalian epidermal cells, fish epidermal cells at all levels are capable of cell division.  During wound healing, cells migrate rapidly to cover any defect and restore the waterproof integrity of the skin.

Unlike mammalian epidermal cells, fish epidermal cells at all levels are capable of cell division.  During wound healing, cells migrate rapidly to cover any defect and restore the waterproof integrity of the skin.

 

====Dermis====

====Dermis====

The dermis of fish consists of a '''''stratum spongiosum''''' and a deeper '''''stratum compactum'''''.  It also contains '''chromatophores, mechanoreceptors, chemoreceptors''' and '''electroreceptors'''.

The dermis of fish consists of a '''''stratum spongiosum''''' and a deeper '''''stratum compactum'''''.  It also contains '''chromatophores, mechanoreceptors, chemoreceptors''' and '''electroreceptors'''.

*In fish, the '''lateral line''' is a sense organ used to detect movement and vibration in the surrounding water.  Lateral lines are usually visible as faint lines running lengthways down each side, from the vicinity of the gill covers to the base of the tail.  Sometimes parts of the lateral organ are modified into electroreceptors, which are organs used to detect electrical impulses. It is possible that vertebrates such as sharks use the lateral organs to detect magnetic fields as well.  Most amphibian larvae and some adult amphibians also have a '''lateral organ'''.

*In fish, the '''lateral line''' is a sense organ used to detect movement and vibration in the surrounding water.  Lateral lines are usually visible as faint lines running lengthways down each side, from the vicinity of the gill covers to the base of the tail.  Sometimes parts of the lateral organ are modified into electroreceptors, which are organs used to detect electrical impulses. It is possible that vertebrates such as sharks use the lateral organs to detect magnetic fields as well.  Most amphibian larvae and some adult amphibians also have a '''lateral organ'''.

 

*'''Fins''' are modified structures of the skin that aid locomotion and balance in the water (and on land).

*'''Fins''' are modified structures of the skin that aid locomotion and balance in the water (and on land).