twitter

 

Previous Ocean Watch columnOcean WatchNext Ocean Watch column

Monday, April 3, 2000

Why donít fish close
their eyes to sleep?

ONE afternoon last week, my 10-year-old nephew and his friend sat on the floor near my desk playing Trivial Pursuits Junior. I wasn't paying much attention to them until I heard the question, "Why don't fish close their eyes when they sleep?"

My nephew didn't know -- and neither did I. Delighted at our ignorance, the friend shouted out the answer.

Days later, the sleeping fish thing still bugged me. Were all the questions that tricky? I gathered the game cards and found 25 other marine questions. You be the judge of their level of difficulty:

1. Do baby seals know how to swim at birth?

2. What name describes a tornado that forms over a calm sea?

3. What type of fish is known for its lack of scales?

4. What's the biggest ocean in the world?

5. What will happen to a starfish that loses its arm?

6. Where are a crab's teeth?

7. Is it possible for a whale to drown?

8. What's the average number of penguins a polar bear will eat per day in the wild?

9. Are sponges plants or animals?

10. Why don't fish close their eyes when they sleep?

 

Answers:

1. No. Unlike whales and dolphins, baby seals are born on land and need intensive care from their mothers before they can survive in the ocean. This includes nursing the pups with milk containing about 50 percent fat and protecting them from predators.

After a baby seal is weaned, it often sticks around its birth area for a while learning how to swim and forage in the safety of shallow water.

2. A waterspout.

3. Catfish. OK, catfish aren't marine but they are grown in some of Hawaii's aquaculture ponds for food. These nocturnal fish have whisker-like barbells around the mouth and venomous spines on their back and side fins. But they don't have scales.

4. We're in the middle of it: the Pacific Ocean.

5. It grows a new one. Starfish (sometimes called sea stars) exhibit amazing powers of regeneration. If an arm is eaten or broken off, starfish grow a new one. If at least one-fifth of the central disc is attached to a lost arm, it can grow into an entire new starfish.

Regeneration is slow. It can take a whole year for a new starfish limb to be complete.

6. In their stomach. Crabs have three teeth in a chamber called the gastric mill, where food is chewed. This chamber is comparable to gizzards in birds.

7. Yes. All whales breathe air and can drown if held under water longer than they can hold their breath. Humpback whales can stay down for as long as 45 minutes. Usually, however, they take a breath at the surface every 10 to 15 minutes. Calves breathe every 3 to 5 minutes. If trapped underwater in fishing nets or lines, whales will most certainly drown.

8. None. Polar bears live only in the Arctic whereas penguins live only in the Antarctic (and other parts of the Southern Hemisphere). The two animals would never cross paths except in a zoo.

9. Animals. Weird animals. Sponges don't move and don't have organs. Because of this the ancient naturalist Aristotle declared sponges plants. Then in 1765 someone noticed water currents running through sponges and determined that they were actually primitive animals.

10. They don't have eyelids, of course.

Got some wrong? So did I. But since I have now cheated, the next time the kids ask me a question from this game, I'll know the answer.

 

 


Marine biologist Susan Scott writes the newspaper column, "Ocean Watch",
for the Honolulu Star-Bulletin, www.starbulletin.com