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Last week, when workers bulldozed Kailua's Kaelepulu Stream to open it to the ocean, some pufferfish swam into the shallow stream. Later, a pet dog bit into one of these pufferfish, and to the horror of onlookers, died within minutes.

The woman who told me this story wondered if there should be a public warning about these dangerous fish.

Yes, there should be a warning, and here it is: Never, ever, eat any part of a pufferfish or let your pet get its teeth into one.

Pufferfish contain tetrodotoxin, one of the world's most potent nerve poisons. A concentrated dose of it can kill an adult in less than 20 minutes. One person (not in Hawaii) died only 17 minutes after eating a piece of pufferfish.

Tetrodotoxin is 160,000 times as potent as cocaine at blocking nerve conduction. This may sound like a free way to get high, but eating any of these fishes' flesh is tempting death. And what a horrible death it is.

A victim of serious tetrodotoxin poisoning first feels numbness or tingling around the mouth, often accompanied by nausea. The numbness soon spreads over the face and inside the mouth, giving the person slurred speech. As the poison spreads throughout the body, it paralyzes muscles. Death comes from being unable to draw a breath.

As if that isn't bad enough, victims are usually conscious during all this. Even though the person cannot move or talk and looks unconscious, the brain stays awake. In other words, poisoned people are aware that they are suffocating.

In spite of (or perhaps because of) this potential danger, some people eat pufferfish to get high. In Japan, pufferfish is a delicacy because diners supposedly experience a sense of euphoria after eating it. There, people prefer a pufferfish of the genus Fugu (not found in Hawaii), thus the name fugu for this potentially lethal dish.

In Japan, specially trained chefs must pass rigorous licensing tests to prepare fugu in restaurants. This law has decreased the number of deaths in Japan from about 100 per year earlier in the century to about five per year in the past decade. None of these recent deaths came from poisoning in Japanese restaurants; they involved fishermen who prepared their own fish.

It's illegal for any restaurant to serve fugu in Hawaii. Rumor has it, however, that you can get it (no doubt at great expense) if you know where to go. If you find such a place, don't be tempted. Seven deaths from pufferfish poisoning have been recorded in Hawaii, all from the stripebelly pufferfish (Arothron hispidus), called keke or o'opu hue in Hawaiian.

Pufferfish aren't the only animals to contain tetrodotoxin. Ocean sunfish have the poison, as do certain starfish, crabs, snails, worms and even some kinds of red algae. Australia's blue-ringed octopus is a famous tetrodotoxin carrier. Some frogs and newts have it, too.

Most of these animals use their tetrodotoxin for protection only. For example, Hawaii's pufferfish secrete tetrodotoxin into the surrounding water when threatened. The exceptions are several ribbon worms and the blue-ringed octopus, which use their potent poison to immobilize prey.

Because tetrodotoxin is found in such a wide range of animals, some researchers believe that bacteria living on or in the host make the deadly poison.

Although pufferfish can kill you, they are not our enemy. These charming fish paddle around slowly, often in shallow water, minding their own business. As long as you -- or your dog -- don't try eat them, pufferfish are fun to watch and harmless.