Vertebrates 5b - Fish integument Flashcards
Notable characteristics of fish skin
Many mucous glands = decrease friction, defense (hagfish); granular glands for toxins - lion fish; photophores produce light (chemoluminescent) by enzymes releasing photons as they break down nutrients (bacteria involved)
Photophores in species
Flashlight fish can turn on/off for communication by covering with skin; angler uses it as lure
Mucous
Bunch of glycoproteins that stick together, serves to lubricate
Early scales
Dermal armour (cosmoid plates) in extinct fish; bone in the skin.
Structure of dermal armour
Basically a layer of bone: enamel (hard!), cosmine (dentine) and vascular bone. Heavy, not flexible, but super protected.
Why did early fish have such intense dermal armour?
Massive invertebrate aquatic scorpion beasts!!
Extant fish scales
mainly bone, but thin and overlapping. Develop from dermis, covered in some epidermis with mucous glands.
Advantage of overlapping scales in fish?
They can bend better; lighter; still some protection
Chromatophores in fish
Just below the dermis, above the subcutis
Cosmoid scales
Rare, in actinisia and some dipnoi. Large, contain cosmine (harder).
Ganoid scales
In gar pike, bichirs. Thick, rectangular. Ganoine replaces cosmine. More primitive
Cycloid and ctenoid scales
Most bony fish. Calcified, overlapping, circular annular layers (grow as fish grow). Very thin. Ctenoid have cteni which help anchor.
Info we can get from scales
Get DNA, learn about its envrionment. Annular layers are like tree rings which can give age; Can determine if it was a bad year of growth if smaller.
Two groups of ray fins and their scales
Soft ray-finned fishes have cycloid scales, and hard/spiky ray-finned fishes have ctenoid
Placoid scales
aka dermal dentricles. In chondrichthyes. Non-overlapping. Similar to teeth and contains pulp cavity, dentine and enamel. Probably degenerate armour.
