Fish scales
scales on fish are big when a fish needs lots of protection but doesn't need to move fast (bigger scales are heavier) and small when a fish need to move fast(smaller scales are lighter).Scales can actually get to the point where they are microscopic, like in the common eel, Anguilla Anguilla. on the cyclostomes, hagfishes and Lampraeys, there are no scales at all, though fossil evidence suggests their distant ancestors did. there are 2 main types of fish: cartilaginous fish and bony fish. scales on bony fish envolved in 4 layers; dense bone, spongy bone, dentine, and enamel. this type of scales are called "cosmoid" and only exist today in fossils. today, scales only have two layers; a calcified one and a fibrous one. there are two main types of scales on bony fish today; ganoid and elasmoid. ganoid scales are hard. elasmoid scales are more flimsy. as a summary, scales are important to fish. for more information, go to: http://www.earthlife.net/fish/scales.html |
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