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Sunday, Sep. 9, 2012

NATURAL SELECTIONS

My seminal link with manga god Osamu Tezuka


In this month's column I am going to claim an audacious link with that great "god of manga," Osamu Tezuka.

News photo
Boy wonder: "God of manga" Osamu Tezuka holds a doll of his most famous creation, Tetsuwan Atomu (known to English-speaking fans as Astro Boy). The photograph was taken in Tezuka's studio in May 1963 — less than five months after "Tetsuwan Atomu" was launched to immediate mass acclaim as Japan's first full-fledged television anime series. KYODO

Though he is most famous for the nuclear-powered, peace-loving robot child he named Tetsuwan Atomu (known to English-speaking fans as Astro Boy) — a character he claimed he was inspired to create after an attack by a drunken GI — Tezuka's millions of fans have also enjoyed his stories of the genius Black Jack, a maverick illegal doctor, and Kimba the White Lion among many, many others.

It's widely believed that as a young man Tezuka qualified as a medical doctor, though up to the time he died at the age of 60 in 1989, he had never practiced medicine. This is what his English-language Wikipedia entry says, and it makes good sense. After all, he clearly knew a lot about surgery, as "Black Jack" is drawn with great anatomical accuracy.

But it appears that it wasn't medicine or surgery that Tezuka qualified in. In fact it was something closer to my own interests as a young man: sperm.

Don't go away — it's not what you might be thinking. I followed a link on Twitter this week to a little-known 1960 publication of Tezuka's in the Journal of the Nara Medical Association (see for yourself here: hdl.handle.net/10564/1075) It turned out that this was Tezuka's PhD dissertation, titled "Electron microscope study on membrane structure of atypical spermatids."

From what I've been able to piece together, Tezuka did a PhD, not a medical degree. He worked on a freshwater gastropod mollusk, the delightfully named Japanese mystery snail.

The idea that Tezuka was a medical doctor who never practiced medicine just seems to have taken off because he had earned a doctorate, and because of "Black Jack." But that legend — notwithstanding its repetition in Wikipedia — is wrong.

Leaving aside the fact that Tezuka was a creative genius whose manga style and influence are still felt today, we have something in common, as for the first few months of my PhD, I also performed electron microscope studies of sperm.

You can be forgiven for questioning why people do this.

Tezuka did it because he was at the time torn between science and his fledgling career as a manga artist. Fascinated by science from childhood, Tezuka divided his time between lab work and drawing, but eventually had to decide which one to devote himself to.

The choice was not easy — at the time, there wasn't much of a prospective career for a manga artist — and Tezuka consulted his mother. "You should work doing the thing you like most of all," she counseled. Tezuka chose manga — but not before getting his PhD from Nara, where he studied the Japanese mystery snail because it apparently has unusual sperm.

These snails, which are commonly kept in aquaria, eat only algae and reproduce in an unusual way for an invertebrate: Rather than laying eggs, they give birth to live young.

To study the sperm, Tezuka would have first "fixed" samples of the snail in a wax-like medium before making very fine salami slices of the block. Those sections are then examined under an electron microscope, which can resolve components of the cell structure.

This is also what I did. I was looking at another species with unusual sperm: the silkworm, an insect that has been bred for more than 5,000 years in China.

They are amazing animals. They have been bred for so long by humans that they have lost the ability to reproduce on their own: They require humans to bring them together. They have also lost the ability to fly. But they still beat their wings, and when they crawl over your hand, you feel tiny gusts of wind from their wings, like mini fans directed at your skin.

But it is the larvae — the caterpillars of the silk moths, known as silkworms — that are the valuable commodities. That's because of the silken cocoon they spin around themselves when they are ready to transform into moths — and from which we get our silk. In fact it's estimated that the world's silkworms produce some 113 billion km of silk filament per year.

And here's why I briefly studied them: Like all butterflies and moths, silkworms have two types of sperm, produced in a roughly 50:50 ratio of ones with cell nuclei containing the DNA needed to fertilize the egg, and ones containing no DNA that are therefore unable to fertilize eggs. A sperm that can't fertilize an egg! What good is that?

That's the mystery, and while there are lots of ideas — the best among them being that the dud sperm are used as some kind of soldiers to fight off the sperm from other males in order to give their DNA-carrying brothers a chance — there is no consensus on their function.

Sadly, too, the summary of Tezuka's PhD doesn't make it clear just what is so unusual about the snail's sperm. In fact, reading it — a very dry description of the fine structure of the sperm cell — makes me feel that his choice to pursue a career in manga might not have been so hard after all.

Rowan Hooper (@rowhoop on Twitter) is the News Editor of New Scientist magazine. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is "Hito wa Ima mo Shinka Shiteru (The Evolving Human)."


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