Chinese giant salamander

The Chinese giant salamander (Andrias davidianus) is one of the largest amphibians on Earth.

These fully aquatic animals live in rocky mountain streams and lakes. They are mostly found in the Yangtze river basin of central China. Because their family, Cryptobranchidae, dates back 170 million years, they are often called "living fossils." They are among only five or six known living species in this ancient family. Other relatives include the Japanese giant salamander and the North American hellbender.

This species has a very specialized way of eating underwater. Because they have poor eyesight, they rely on sensory nodes. These are special spots that run in a line from the head to the tail. These nodes allow the salamander to sense tiny vibrations in the water. When prey is near, they use a process called bidirectional flow suction feeding. The salamander moves slowly toward the prey first. Then, it abruptly gapes its wide, flat mouth open.

This motion creates a high velocity of water that shoots the prey into the mouth. To finish the meal, the salamander closes its mouth but leaves a small gap. This gap allows the captured water to escape.

Digestion is also a highly adapted process for these large animals. Their esophaguses have four different layers to help move food. One layer contains strong muscular tissue to push food toward the stomach. Another layer has ciliated cells that move mucus over the surface. This mucus lubricates the throat to reduce friction from large items like whole crabs. They also possess a very strong bite force. This is partly because they are missing a bone usually found in the cheek region of other salamanders. Their liver also helps them survive long periods without food. The liver can regulate proteins to manage metabolic reserves during fasting.

For a long time, scientists believed there was only one species of Chinese giant salamander. However, recent genetic evidence shows the group is much more complex. A 2018 study of mitochondrial DNA revealed five wild clades, or distinct genetic groups. These groups diverged from each other between 4.71 and 10.25 million years ago. Some scientists believe these should be recognized as cryptic species. These are different species that look very similar but are genetically distinct. In 2019, one clade was identified as Andrias sligoi. In 2022, another was described as Andrias jiangxiensis. In 2023, a species from the Huangshan mountains was named Andrias cheni.

Understanding these different groups is vital because the wild population is in trouble. The Chinese giant salamander is considered critically endangered. Since the 1950s, the wild population has declined by an estimated 80%. This decline is caused by habitat loss, pollution, and overcollection. They are often collected because they are considered a delicacy and used in traditional Chinese medicine. While they are farmed extensively in central China, many farmed individuals are still caught in the wild. They are protected under Chinese law and listed under CITES Appendix I. The Evolutionarily Distinct and Globally Endangered project named them a "focal species" in 2008.

There are many interesting facts about their size and behavior.

An adult can reach significant weights and lengths. One documented individual in Zhangjiajie in 2007 was exceptionally large. Another individual found in a Chongqing cave in 2015 also surpassed typical maximum weights. Their sounds are so unique that they are known in Chinese as "infant fish" (Wáwáyú). This is because their vocalizations can sound like a crying human child. They also produce a sticky, white skin secretion to repel predators. During breeding, females lay 400 to 500 eggs in underwater cavities. The males then guard these eggs for 50 to 60 days until they hatch.

Finally, the movement of these animals has changed their natural environment. They have been introduced to the Kyoto Prefecture in Japan. This has created a problem because they hybridize with the native Japanese giant salamander.

A 2024 genetic study confirmed that the species in Japan is the "true" Andrias davidianus. This hybridization can threaten the genetic purity of local species. The Chinese giant salamander remains a complex subject for biologists. Their deep history and current struggles make them a vital part of global conservation efforts.