Otto the octopus didn’t appreciate the spotlight shining on his laboratory tank at night. So he turned it off. In fact, he turned off the lights in the whole lab.

Octopuses are smart and curious. They use tools and learn from watching other octopuses. They can solve mazes, open the lids of glass jars, and build dens.

In the lab, they learn to tell people apart. They’ve been known to take a disliking to some of the lab workers, squirting jets of water at them when they walk by. And they can show a clear preference for the people who feed them.

Octopuses also play. In one study, scientists put some small, sealed plastic bottles in octopus tanks. Some of the critters fired jets of water at the bottles, bouncing them off the walls. Others fired a bottle toward the tank’s inlet valve, so the bottle came back to them—like octopus ping-pong.

And that brings us back to Otto. Scientists in Germany were studying the behavior of Otto and several others. Otto was the most active. He damaged the glass walls of his tank by throwing rocks at them, and he sometimes rearranged the stuff in the tank.

A 2,000-watt spotlight shined on the tank at night. But several times, the light shorted out—and so did the rest of the lab. Scientists then spent the night in the lab to figure out what was happening. Otto was climbing to the rim of the tank and squirting water at the light. That turned out the lights—perhaps allowing Otto to get a good night’s sleep.

A rare species of sponge found in the Red Sea and Indian Ocean has a rare distinction: It has levels of a metal that are thousands of times higher than ever seen in any other organism. And most of that metal is stored away by a type of bacteria that lives inside the sponge.

Sponges are filter feeders—they draw in water, filter out food and other solid bits, then shoot the water and solid particles back into the sea. Some contaminants can lodge inside them. Some studies have found high levels of arsenic, barium, and other toxic substances.

A more recent study looked at the species called Theonella conica. It’s found down the eastern coast of Africa. Up to 40 percent of its body weight consists of bacteria and other microscopic organisms, many of which have a symbiotic relationship with the sponge.

Over two decades, researchers collected specimens from Zanzibar, off the southeastern African coast, and the Gulf of Aqaba, at the northern tip of the Red Sea.

When they analyzed the sponges, the scientists found extremely high levels of molybdenum. The metal is important for the metabolism of people and other animals, but only at low levels. At high levels it’s toxic. So the metal may help protect the sponges from predators.

The element was concentrated in one of the species of bacteria inside the sponge. It changes the material into a harmless mineral, which is flushed back into the water—keeping the sponge safe from both predators and the toxic element.

The journey around Cape Horn, at the southern tip of South America, is one of the most treacherous in the world. The cape has claimed hundreds of ships and thousands of sailors. Not many commercial vessels make the journey today. But for sail-powered yachts, rounding the cape is a big attraction—like climbing Mount Everest.

Cape Horn is named for the home town of the Dutch navigator who described it, in 1616. It’s a small island that features a cliff a quarter of a mile high.

The cape is where the Atlantic and Pacific oceans meet. The confluence generates strong currents. Those currents are magnified by the contours of the ocean floor, which features many sunken islands.

The region is in the “Furious Fifties”—latitudes of more than 50 degrees south. Strong winds blow from west to east. Those are funneled by the mountains of South America and Antarctica. That creates a wind tunnel effect, so winds almost always blow at gale force. And they frequently top hurricane force, battering any ships that challenge the passage.

In addition, icebergs are common features, and storms bring heavy rain, hail, sleet, and snow. That all combines to make a journey around Cape Horn especially challenging.

The opening of the Panama Canal, in 1914, provided a safe shortcut between the east and west coasts of the Americas. But big tankers, naval vessels, cruise ships, and private yachts still round the cape—one of the most dangerous ocean voyages in the world.