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You might think, “An old man…?” but it really exists. The reason for the name is that the fish’s face looks like a man with a long beard—its appearance resembles an old man. There’s even another fish with the alternate name “old lady.”

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In pictures and illustrations, fish often appear toothless, but they actually have proper teeth. However, the size and number of teeth vary depending on the species and what they eat. Fish that feed on small fish or shellfish have sharp, well-developed teeth.

want to

Sea bream, often served as a festive celebratory dish, is called the “king of fish.” Other reasons include that its sturdy scales are said to resemble a samurai’s armor and helmet.

whale shark

The whale shark, which is very popular in aquariums, is the largest fish in the world. When we think of sharks, we often imagine fearsome carnivores, but despite its huge body, the whale shark mainly feeds on very small plankton.

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You might think they’re called pufferfish because they have 1,000 spines, right? And in fact, that is the reason for the name: they seem to have a lot of spines—about a thousand or so. However, it’s said that in reality they have only about 350 to 400.

When you feel in danger

When a pufferfish senses danger, it inflates its body to about twice its usual size to show its opponent how big it is. Inside the pufferfish’s body is a sac into which it rapidly pumps water or air, causing its body to swell.

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Dolphins swimming gracefully in the sea. Although dolphins also perform in aquarium shows, they are not actually fish. Dolphins are mammals, just like humans. Fish hatch from eggs, but dolphins do not; like humans, they give birth to baby dolphins rather than laying eggs.

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Human and animal eyelids are there so they can blink and keep their eyes from drying out. Fish live in water, so their eyes don’t dry out, and they don’t have eyelids.

gills

Humans breathe with their lungs, inhaling and exhaling through the mouth, while fish breathe with gills. Gills perform the same function as human lungs, but because water contains less oxygen than air, gills take in oxygen efficiently.

tuna

Tuna have to keep swimming at high speed to take in oxygen, so if they stop, they can’t breathe. Not only tuna but also other “migratory fish,” such as mackerel, sardines, and bonito, are companions that keep swimming.