Fish fin
Videos
Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles.
Dorsal fin of a chub (Squalius cephalus)
Skeleton of a lingcod, a ray-finned fish
Lobe-finned fishes, like this coelacanth, have fins that are borne on a fleshy, lobe-like, scaly stalk extending from the body. Due to the high number of fins it possesses, the coelacanth has high maneuverability and can orient its body in almost any direction in the water.
Pectoral fin with fleshy lobe of Latimeria chalumnae (Citron / CC-BY-SA-3.0)
Fish scale
Videos
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages. The term scale derives from the Old French escale, meaning a shell pod or husk.
Cycloid scales cover these teleost fish (rohu)
Lobe-finned fishes, like this preserved coelacanth, have elasmoid scales.
The scales of this spotted gar appear glassy due to ganoine.
The alligator gar has a tough armouring of rhomboidal-shaped ganoid scales.