It's the most celebrated and notorious fish in the world, certainly in culinary circles. Now the puffer fish — one of Japan's most enigmatic creatures — meets some of biology's deepest questions: Why did sex evolve? Why are there two sexes? Why is the male sex chromosome such a puny little thing?

I'll admit right away that the puffer fish, better known in Japan as fugu, won't provide answers to these questions. But just the story of why an animal usually discussed in sushi shops is the subject of research by a Nobel Prize-winner and scientists at the University of Tokyo is interesting enough, without having to solve deep evolutionary problems.

Kiyoshi Kikuchi at the Fisheries Laboratory in the University of Tokyo Graduate School of Agricultural and Life Sciences works on the tiger puffer fish (torafugu; Takifugu rubripes). This, among several species of fugu, is the one most often eaten, and most often used by scientists.