Today’s Wonder of the Day was inspired by Julian. Julian Wonders, “Why do sharks need nostrels when they have gills?” Thanks for WONDERing with us, Julian!

When you think of a shark, you probably think of their large mouths full of many sharp teeth! You might also imagine their dorsal fin pointing up out of the water as they swim. But have you ever WONDERed about some other parts of their bodies? We know they have mouths, teeth, fins…what about noses? Do sharks have nostrils—and if so, why?

Shark noses don’t look like human noses, that’s for sure! But they do have noses, and their noses have holes like ours do. Instead of nostrils, their nose holes are called nares. And, of course, their noses work a little differently than ours do. Our noses are used for breathing air and smelling. Tiny pieces of whatever we are smelling enter our nostrils when we breathe in. When a smell enters our nostrils, receptors in our noses send messages to our brains. Then, our brain interprets those signals.

But sharks don’t breathe air like we do. Instead, they use gills to take oxygen from the water. Their nostrils are not connected to their gills—or even to their mouths! So how do they smell? First, water enters one of their nares. It will move through a nasal sac, or passage, and out the other nostril. As the water passes through the nasal sac, the shark’s receptors will pick up odors. Just like in our brain, the receptors will then send messages to the shark’s brain.

The part of a shark’s brain that interprets messages about smells is much larger than the part in a human brain. That makes sense, because smells are very important to a shark. In fact, smells help sharks find the food they need to live! Scientists used to think that sharks could smell better than many other fish. This was, in part, because there is much more area in their nasal sac. They thought that this extra area with smell receptors would give sharks a much better sense of smell. Although sharks do have a great sense of smell, it turns out that it is about the same as most other fish.

But sharks aren’t just great at smelling. They have other senses just like we do—taste, sight, touch, hearing—plus some others that we don’t have! Their sense of hearing is even better than their sense of smell. Because sound waves travel faster and farther through water than through air, sharks can hear sounds over great distances. Sharks also have a system called the lateral line. This is a group of fluid-filled sacs just under their skin. It helps sharks feel the flow of water around them. It can also detect small pressure changes—as when a fish might be moving around close to them.

Another sense that sharks have is their “electric” sense. They can detect electromagnetic fields. This can help them navigate the oceans because of the electromagnetic fields around the earth. It can even help them find prey, since all living things give out weak electrical signals.

From smell to hearing to electrical sense, shark senses have interesting differences to ours! What shark sense would YOU like to have?

Standards: CCRA.R.1, CCRA.R.2, CCRA.R.4, CCRA.R.10, CCRA.L.2, CCRA.L.3, CCRA.L.4, CCRA.L.5, CCRA.L.6, CCRA.W.3, CCRA.W.4, NGSS.LS1.A, NGSS.LS1.D

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