Jeff Rotman / Close-up of scales of the Yellowbar Angelfish (Pomacanthus maculosus). Red Sea, Egypt.

Doug Perrine / Bait ball of schooling Anchovies (Encrasicholina punctifer) with sparkling scales from dead fish drifting downward through the water; Kei ( or Kai ) Islands, Moluccas, eastern Indonesia, Banda Sea, So...

Nick Hawkins / Brook trout (Salvelinus fontinalis) close up of skin / scales, Miramichi River, New Brunswick, Canada, June.

Nick Hawkins / Atlantic salmon (Salmo salar) close up of skin scales, Miramichi River, New Brunswick, Canada, June.

Lucas Bustamante / Spotted fish-scaled gecko (Geckolepis maculata) close up of scales, Palmarium, Atsinanana, Madagascar.

Paul D Stewart / Woodcut illustration of dolphin's placenta, skull and birth by Gesner. Gesner 'Icones Animalium', 1560. Generally animals were grouped by habitat, so dolphins were thought of as fish. However Gesner d...

Alex Mustard / Blue-striped fangblenny (Plagiotremus rhinorhynchos) peeking out of its hole in coral reef. These small fish live in holes but dart out to eat the scales from other fish. Sinai, Egypt. Gulf of Aqaba,...

Solvin Zankl / Yellow-ribbon sweetlip (Plectorhinchus polytaenia) close up of stripes, Raja Ampat, West Papua, Indonesia, Pacific Ocean.

Aflo / Crowd of tourists watching Whale shark (Rhynchodon typus) in the Kuroshio sea exhibit, Okinawa Churaumi Aquarium, Ocean Expo Park, Okinawa Commermorative National Goverment Park, Okinawa Main Island,...

Alex Mustard / The skin of a Tassled wobbegong shark (Eucrossorhinus dasypogon), showing the rough placoid scales, commonly called denticles. These scales have the same structure as the shark's teeth and are as roug...

Alex Mustard / Skin of a nurse shark (Ginglymostom cirratum) showing the rough placoid scales, commonly called denticles. These scales have the same structure as the shark's teeth and are as rough as sandpaper when...

Michel Roggo / Close-up of Atlantic Salmon (Salmo salar). Salmon hatchery, France. Captive.