Maggot mysteries

SCIENCE CAN FIND inspiration in the strangest of places. Take maggots. Most of us don’t like maggots. We think these larval stages of insects are dirty and smelly, and the way they wriggle is creepy. But the lowly maggot is providing scientists and physicians with a valuable ally in the battle for knowledge and against disease.

Shortly before Easter, I organized a scientific meeting devoted solely to the behavior, anatomy and development of maggots. Gathering 70 researchers from Europe, the U.S., Chile and Japan, the Manchester Maggot Meeting showed how much this tiny animal can teach us.

For most of humanity’s history, most people -- from ordinary folk to great thinkers like Aristotle -- have assumed that maggots appear spontaneously in filth. This was not stupidity on their part; it’s what seems to happen. One day you have some fresh meat, the next day it has maggots on it.

It was only in the 17th century that the great Italian physician, Francesco Redi, used careful observation and astute experimentation to demonstrate that maggots turned into flies, which laid eggs out of which hatched maggots, thereby demonstrating that -- for macroscopic organisms at least -- there was no such thing as spontaneous generation, and making insects and other small organisms full members of the animal kingdom.

A far bigger mystery, which Redi’s contemporary, the Dutch scientist Jan Swammerdam, tried to resolve, was how a maggot turned into a fly. Like Redi, Swammerdam managed to convince people that the maggot and the fly were the same organism. But he could not show how a legless, wingless larva is transformed into a hairy, buzzing fly. Science is still trying to understand exactly what is going on in this near-magical process of metamorphosis.

The study of maggots has taken on an even greater importance because of the tiny fruit fly, Drosophila. At the beginning of the 20th century, Drosophila became the key organism in genetics. Recently, more and more of us have started to look at larvae.

When it was first suggested that I should switch my attention from adult flies to maggots, I was dismissive. “They’re stupid and simple and don’t do anything much,” I said. It took me some time to realize that those were in fact some excellent reasons for working with maggots. Science generally progresses fastest when it looks at simple examples.

For instance, I study the sense of smell. Most scientists look at smell in mice and rats, which, like us, have tens of millions of cells devoted to detecting odors. However, a fly has about 1,300 on each antenna, while a maggot has a mere 21 odor-receptor neurons on each of its two “noses.” Despite this incredible simplicity, the maggot’s brain (yes, a maggot does have a brain) processes the smells in essentially the same way as you or I.

At the meeting in Manchester, England, researchers showed how maggots with only a single cell in their “nose” were still able to respond to a wide range of odors.

This kind of research is helping provide answers to a mystery that goes back to the ancient Greeks -- why does a smell smell?

Probably the most far-reaching finding at the meeting came from researchers based in Germany who, several years ago, set out to find out what happens when a maggot is hungry (which is most of the time).

First, they showed what genes got turned on and off when the larva had an empty stomach. Then, they discovered that one of these genes was active in a handful of cells in the brain that control feeding. Finally, they discovered that there was a similar gene in mammals, which is involved in feeding activity. If you block the gene in mammas, you get fat rats.

This work from maggots is directly contributing to our understanding of the obesity epidemic sweeping the Western world.

Some of the best bits of scientific meetings are the informal discussions. This time, I learned how maggots can also directly help patients with the debilitating condition known as “diabetic foot.” Large, flesh-eating maggots are placed on the wound and gently nibble away at the dead skin. Within a few days, the result is a clean wound, lower levels of bacterial infection and increased recovery rates.

“Maggot therapy,” first developed in the West during the U.S. Civil War, is now growing in popularity on both sides of the Atlantic. Despite the “yuk factor,” patients seem to accept this cheap and very effective therapy.

Larvae demonstrate that pure research, sometimes on the most unlikely species, can provide remarkable insights and even materially improve our lives. The next time you find a maggot on a piece of rotting fruit or meat, hesitate an instant before you throw it in the trash.

Think about what it might be able to teach us.