Fifteen giant salamanders, dubbed living fossils due to their skeletons' similarity to those of their ancestors millions of years ago, have died after being put on show at the World Expo 2010 in Shanghai as a result of the hot weather and noisy environment.

The skeleton of the giant salamander, the world's largest living amphibian, is almost identical to that of fossils from 30 million years ago. The 15 salamanders had been on show at the Shaanxi Pavilion since July 27.

The largest of the salamanders reached 1.4 meters in length and weighed 20 kilograms, and was bred through artificial propagation.

Environmental changes have led to a rapid decline in the number of wild salaman-ders. As a result, it has been listed as a national aquatic wild animal under second-class protection.

Chen Wenyou, from the Shaanxi Chamber of Commerce in Shanghai and organizer of the exhibition, said the giant salamanders prefer a quiet environment, while the large influx of visitors to the pavilion frightened the salamanders and caused them to be restless.

"The largest salamander was 16 years old. What a pity we lost it," said Dai Mingheng, chairman of Shaanxi Xushui Bio-development Company, which provided the largest giant salamander for the Shanghai Expo.

Camera flashes from tourists taking pictures may have significantly affected the salamanders, who normally live in dark conditions.

"The temperature suitable for their growth is around 18 C to 23 C, and temperature for living is around –4 C to 32 C. But July is the hottest month in Shanghai, so the salamanders were finding it hard to survive," he said.

Dai said the air conditioners at the pavilion were turned off at night. Although the workers responsible for the salamanders added ice to lower the temperature, nine salamanders died at the pavilion. The other five all died after being taken home by Dai, and the last one died in Shanghai on August 10.

"We didn't have enough experience since it was the first time we attended the exhibition. We should have taken emergency situations into consideration," Dai said.

The bodies of 10 of the salamanders are currently frozen, and may be donated for research pruposes afterward