KASHIHARA, NARA PREF. – The Japanese giant salamander, a rare amphibian often called a “living fossil,” could disappear as a distinct species as interbreeding with its Chinese relative increases.
Over the years, Japanese and Chinese giant salamander hybrids have proliferated in western Japan, triggering alarm bells and a flurry of activity to preserve the native species.
The Japanese giant salamander, which at up to 1.5 meters long is the world’s second-largest amphibian after its Chinese relative, inhabits rivers and streams in the Chugoku, Kinki and Chubu regions.
The creature is called a living fossil because it remains strikingly similar to its ancestors 30 million years ago.
In 1952, the government designated the native species, which used to be hunted as food, a “special natural monument.” It has since been afforded legal protection.
While this has helped prevent the aquatic amphibian from going extinct in the wild, it is still threatened by habitat destruction, population fragmentation, and now interbreeding with the larger, nonnative species.
Authorities and biologists are investigating how much hybridization between Japanese and Chinese salamanders has occurred in Kyoto, where the interbreeding problem has become especially acute, and other prefectures.
However, distinguishing between the native species and hybrids by appearance alone is difficult. Identifying them requires DNA analysis.
As concerns over the extent of interbreeding have grown, the DNA analysis workload has become onerous.
A research group led by amphibian expert Masafumi Matsui, a professor of biology at Kyoto University, receives more than 100 samples each year from Kyoto and from nearby prefectures, including Mie and Nara.
“This is too much for a single research team,” Matsui said.
Chinese giant salamanders were first imported to Japan in large numbers for eating and for ornamental purposes in the 1970s, before the country acceded to the Convention on International Trade in Endangered Species of Wild Fauna and Flora, which bans trading the species for commercial purposes.
Some of the imported salamanders escaped or were released into the wild and began to breed with the native species.
In recent years, the presence of many hybrids has been found in tributaries of Kyoto’s Kamogawa River and in the Takigawa River in Mie.
In Nara, where a hybridization survey began two years ago, four hybrids have been found, all in Uda, adjacent to a part of Mie where they are found in large numbers.
“The native species is a national treasure,” an official in Uda said. “We can’t afford to allow it to go extinct. We want to stop the increase in hybrids.”
Hybridization of the salamanders is just one example of the problems being caused nationwide by invasive species.
“We do not even know” the full extent of the problem, an Environment Ministry official conceded.
Zenkichi Shimizu, head of a group of nature lovers in Matsusaka, Mie Prefecture, is concerned about the ecological impact that nonnative salamanders might have.
“What’s wrong is not the presence of the Chinese giant salamander or the hybrids. The problem is that the disappearance of the species best suited to Japan’s nature would change the diversity of the environment,” he said.
But preserving the genetic purity of the Japanese species is a major challenge. For one thing, there are few experts who are knowledgeable about this rare creature.
There are growing calls to monitor the breeding situation, but this is no easy task because they are nocturnal and surveying them is difficult.
Moreover, the high degree of legal protection afforded to the native species means that permission from the Agency of Cultural Affairs may be required to handle or move suspected hybrids.
Another issue is how prefectures should work together to preserve the species. For now, captured hybrids are kept at facilities such as Kyoto Aquarium. With the capacity of those facilities stretched to the limit, however, the fate of the hybrids is unclear.
The Environment Ministry has yet to issue guidelines on what to do with the captive hybrids. Some say the only option is to kill them.
Matsui, the Kyoto University professor, blamed humans for threatening nature by failing to consider the consequences of their actions.
“This has happened because the Chinese salamander was imported without much consideration,” Matsui said.
“Humans are disrupting the evolution of living creatures and the history of the creation of diversification that goes on over an immense amount of time. But they are not aware of this fact because they do not see tangible damage, as in the case of agricultural disasters.”
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