See-Through Goldfish Bred

To create the translucent creature, scientists at Japan's Mie University and Nagoya University crossbred fish that had defects in the gene that regulates pigment, or color.

The resulting mutant fish's organs are all plainly visible, Yutaka Tamaru, a life science researcher at Mie University, said via email.

Tamaru said the fish could act both as a living textbook in biology classes and as a tool for medical researchers.

For instance, scientists could watch in real time how an animal's organs develop. They could also get an inside view of how diseases, particularly tumors, progress in the body.

"As this goldfish grows bigger, you can watch its whole life," Tamaru said.

The translucence doesn't harm the goldfish or shorten its life span, he added.