Kids Web Japan

The Living Fossil

(Top) The ceremony in Tanzania to mark the donation of the first coelacanth specimen
(Bottom) The second coelacanth given to Japan was preserved using plastination - a process whereby fluids and fats are replaced with plastic. At the time, this was the largest specimen ever found in Tanzania, measuring 170 centimeters in length and weighing 105 kilograms. (The Tokyo Institute of Technology's coelacanth specimen)

What is a coelacanth?

It's a fish that first appeared in the Earth's oceans about 400 million years ago. The coelacanth was thought to have died out along with the dinosaurs about 65 million years ago, but in 1938 the fish was found to be living in the sea off the coast of South Africa. The coelacanth is a very important animal for understanding the process of evolution, because it shows signs of the transition from fish to land-dwelling animals with four legs. Currently, 20 universities and other organizations in Japan are working together to unlock the mysteries of biological evolution by studying the coelacanth. They have been assisted in their endeavors by the donation of two rare coelacanth specimens from Tanzania, a country on the coast of eastern Africa.

An Amazing Fish

A CAT scan Machine and images from the scan
(Courtesy of Professor Okada Norihiro of the Tokyo Institute of Technology, with cooperation from GE Yokogawa Medical Systems, Ltd.)

• Sturdy Fins
  
  The coelacanth has eight fins on its body, but they are different from those of most other fish. Coelacanth fins are bony, and the lower ones are a lot like legs. By dissecting the coelacanth and studying its muscles and nerve pathways, scientists are trying to determine its relationship to four-legged animals.
  
  A CAT scan machine is a medical device used to get a picture of the inside of a person's body. When scientists used a CAT scan to peer inside a coelacanth, they learned that the bones inside its fins have joints. The images further revealed that the top part of the fish's skull is also structured like a moving joint. This may explain why the coelacanth is able to open its mouth so wide to feed.
• Hard Scales
  
  The outer surface of a coelacanth's scales is covered with a hard enamel, similar to that of human teeth.
• DNA Analysis
  
  DNA analysis has revealed that there is a breeding population of coelacanths living in the waters off the coast of Tanzania.

A Major Discovery in Tanzania

Scientists have glimpsed a rare phenomenon in the waters of Tanzania's Lake Victoria. Over the past 12,000 years, the creatures inhabiting the lake have differentiated into 700 different species. Professor Okada Norihiro of the Tokyo Institute of Technology and other researchers studied the fish living in the lake. It was discovered that their genetic makeup was changing in response to their environment. These mutations have, for example, caused the fish to change color.

In order to attract mates, the males of a certain species of fish that live in the shallower waters of the lake have a blue coloration. Males of the same type of fish from deeper water, on the other hand, have developed a red coloration. This differentiation between males is leading to the evolution of distinct species. The 700 species found in the lake are products of small changes like this occurring again and again over a long period of time.

The ocean seems to be a great place to look for clues that will unlock the mysteries of evolution.

Photos courtesy of Professor Okada Norihiro of the Tokyo Institute of Technology

(Updated in December 2008)