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Breathing Makes a Shark Smile |
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While joy or happy amusement may have nothing to do with it, breathing is a joint venture of the mouth and gills.
Shark gills are different than those of bony fish. Bony fish have one gill, covered by a hard protective plate that is operated by a system of bones and muscles. The action of the muscles pumps water through the fish’s mouth and out through the gills where the water is filtered for oxygen intake. In contrast, a shark has between 5 and 7 pairs of gill slits, depending on the species. Shark gill slits have very little musculature. In most species, sharks must move forward to enable the water to flow through the open mouth and through the gills in order to breathe. The open mouth gives the appearance of a smile in many sharks. Next Quick Shark Fact
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Quick Shark Facts 
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