Why would a scientist talk 11 other scientists into eating tadpoles? To answer a scientific mystery, of course; and also because he could. The incident resulted in a 1971 study called On the Comparative Palatability of Some Dry-Season Tadpoles from Costa Rica.

Tadpoles come in a wild variety of patterns and colours. Most blend in with their surroundings. But some have gaudy patterns or bright colours or both. The question was: Why don't predators wolf down all of these fetchingly packaged snacks? How can they not have gone extinct?

The leading theory said that the eye-catching tadpoles must taste terrible to predators, so yucky as to be spurned. But it was, as they say, "just a theory" - until Richard Wassersug, of the University of California, Berkeley, put it to the test. He did this in Costa Rica, where tadpole species are numerous, and beer to wash them down with is cheap.

Wassersug decided to use substitutes for the natural predators of the tadpole. He used cheap substitutes. He used graduate students.

And he made them follow strict procedures. In his words:

"The tasters were asked to rate the palatability of each tadpole's skin, tail and body on a 1-to-5 scale: 1 tastes good; 2 no taste; 3, only slightly disagreeable; 4, moderately disagreeable; and 5, very strongly disagreeable. They were also asked to make comments about the taste as they went along and to note the most and least palatable tadpole at the end of the experiment. The standardised tasting procedure included several steps. A tadpole was rinsed in fresh water. The taster placed the tadpole in his or her mouth, and held it for 10-20 seconds without biting into it. Then the taster bit into the tail, breaking the skin, and chewed lightly for 10-20 seconds. For the last 10-20 seconds the taster bit firmly and fully into the body of the tadpole. The participants were directed not to swallow the tadpoles but to spit them out and to rinse their mouths out at least twice with fresh water before proceeding to the next tadpole."

The results of the experiment were sparklingly clear. One species of tadpole, Bufalo marinus , was rated the most distasteful by six of the nine tasters, who described it as being "bitter". Several species were found to taste almost good. Generally, the tasters found the bodies to be less palatable than the skin, but more palatable than the tails.

On the whole, the results supported Wassersug's thesis that the more conspicuous the tadpole, the less palatable it is likely to be. Twenty-nine years later, he was awarded an Ig Nobel prize in the field of biology.

Now a professor of biology at Dalhousie University in Halifax, Nova Scotia, Richard Wassersug is a recognised authority on amphibian physiology and medicine. But, as happens to a few great scientists, a most unexpected, most unhappy event gave his life - and his research - a spectacular turn. Details next week, in this space.

· Marc Abrahams is editor of the bimonthly Annals of Improbable Research and organiser of the Ig Nobel prize