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Science & Nature Update

The sperm whale's forehead is filled with oil that cushions blows – but this oil also attracts whalers

Monday 10 June 2002 00:00 BST
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There might be some truth in the story of Moby-Dick, the whale whose reputation derives from the occasion when it repeatedly rams the ship of Captain Ahab in Herman Melville's classic tale of 19th-century whaling. Scientists have found that the head of a sperm whale is perfectly evolved for ramming.

The foreheads of this species of whale contain two sacs filled with oil, which are especially big in males, leading to speculation that they might have evolved to cushion the impact of ramming between rivals engaged in a fight. Although there is scant evidence for such fights, there have been a few anecdotal accounts including the sinking of the Ann Alexander in 1851, which was supposed to have been sunk by two head-on charges by a harpooned whale.

Now, Stephen Deban of the University of Utah has modelled how the fluid-filled sacs of a male sperm whale would behave in a collision. He found that the organ behaves as a damper, cushioning the impact. Deban describes the mechanism as being "like a syringe", according to New Scientist magazine. "You don't need much force to push the water out slowly, but you need to squeeze much harder to push it out faster," says New Scientist.

"That means an attacking whale could smash into an opponent's side and come out of the encounter unscathed. What's more, whale species in which the males engage in more intense competition for mates also tend to have larger fluid-filled sacs." Unfortunately, it was the precious oil in the head of the sperm whale that made it so attractive to whalers.

Cholera – one of the greatest scourges in history – becomes more infectious after is has passed through the human gut, scientists have found. The discovery could explain why the disease spreads so quickly. The cholera bacterium is spread by water or food contaminated with human faeces. Each year the disease infects as many as 300,000 people in developing countries, causing severe diarrhoea that can lead to extreme dehydration and death.

A study has found that as the vibrio bacteria pass through an infected person, something in the intestinal tract, perhaps stomach acid, prompts the microbe to switch on the genes that make it more infectious. Other genes that normally restrict its movement are switched off, making the microbe hyperinfectious.

Andrew Camilli of the Tufts University School of Medicine said that the findings could make it more difficult to develop vaccines against cholera as much of the work is based on laboratory strains of the micro-organism, which have not undergone this genetic transformation.

"That's a problem. Growing bacteria in the laboratory does not reflect what's going on in nature," said Camilli, whose study appears in this weeks's Nature. The work may help, however, in pinpointing targets for drugs designed to fight the disease, Camilli said.

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