Enter the Amphibian and Reptile Museum in the west district of the Beijing Zoo, and on the wall facing the gate is a relief of a giant salamander [ní]. ▼▼▼
It can be seen that the giant salamander is undoubtedly the most heavyweight ornamental animal among the amphibians that occupy the "half of the country" in this museum. In fact, the giant salamander is not only the largest amphibian and a special animal of China, but also a national level II key protected wild animal in China; it was listed in Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora in 1995; listed as a critically endangered (CR) species by the Red Book of Endangered Animals of China in 1998; and listed as a critically endangered species by the Red List of Vertebrates of China in 2016. As a result, the giant salamander is also the flagship species of amphibian conservation.
Another well-known name for the giant salamander is "baby fish", which is said to be named because its nighttime cries like a baby crying. This statement is mainly based on the ancient Chinese book "salamander has four legs, such as turtles and diseases, there is a body of a fish, and with feet, the sound is like a child's cry, the big one is eight, nine feet long..." and other records, as well as in the "Compendium of Materia Medica": "Salamander, in the mountain stream, like a catfish has four legs, long tail, can go up to the tree, sound like a child crying, so it is called a salamander, a human fish." However, the giant salamander rarely makes a sound, at least it is difficult to hear when people visit the zoo. Another theory is that it is called a baby fish because its limbs are fat and short, especially the forelimbs, which are very similar to the arms of a baby, which seems to be more reliable. ▼▼▼
The "baby fish" is so famous, but it is not easy to appreciate it in the zoo, mainly to simulate its natural habitat, the light in the feeding box is relatively dark, the giant salamander is not very active, most of the time hidden under the rocks and other hidden objects. Therefore, appreciating the giant salamander requires a little patience.
We can first appreciate its body shape. The body of the giant salamander is elongated, appearing broad and strong, with a short neck with a more pronounced head, torso, tail and limbs (photo 3), while the laterally flattened tail is very long, reaching one-third to one-half of the body length, and the tail has fins above and below. ▼▼▼
In addition, it has 4 fingers on the forelimbs and 5 toes on the hind limbs, and has micro-webbing between the fingers (toes), but no claws. As the largest amphibian, its body length is indeed extraordinary, the adult body is usually about 1 meter, the longest can reach 2 meters, the weight is mostly 20-25 kg, the largest up to 50 kg, can be described as worthy of the name.
Looking at its head again, the head is wide and flat, the surface has obvious warty grains, the "facial features" are very inconspicuous, it looks like a large stone in the water, with a hidden effect. The eyes located on the back of the head are surprisingly small, like a small spot on a stone, and there are no eyelids, which are the result of degradation due to long-term adaptation to underwater life. The curved mouth crack, like a large crack in the stone, is very wide, and the upper and lower jaws have most of the fine teeth of similar size. This "big mouth" favors its feeding. ▼▼▼
The giant salamander has bare skin on the surface, and there are neither smooth scales like fish, dry scales like snakes, nor feathers like birds and animal hair. Therefore, its body surface is relatively smooth, only scattered with small wart particles, when stimulated, it can secrete a white pulp-like mucus like a peppercorn. There are longitudinal skin folds between the crotches along the side of the body. Rough look, the appearance of the giant salamander seems to lack some color, in fact, it is not, its body color will vary with the habitat, the body color also has a certain difference, the back can be brown, reddish brown, black brown, etc., there are dark irregular markings on the top, and the ventral surface is light brown or off-white. ▼▼▼
In fact, compared to the fossil record, the giant salamander has not changed significantly in its body structure over a period of 160 million years, so it is also known as a "living fossil" animal.
As amphibians, giant salamanders can breathe with their lungs, but because their lungs are not well developed, they are also like frogs, which need to use moist skin for gas exchange as an auxiliary breathing, so they must live in water or near water.
In the wild, the habitat of the giant salamander is mostly located in the upper reaches of rivers and streams, generally distributed in the mountains at the edge of the basin, with higher mountains on both sides and more deep hole undercurrents. The vegetation cover around its habitat is high, the environmental humidity is higher than 80%, the river surface is narrow, the water depth is low, the riverbed is sandy, the river is clear all year round, the water flow rate is slow, the water quality mineralization is high, and the water temperature varies from 5 °C to 25 °C.
Giant salamanders in the wild often hide in caves during the day, with their heads more outward, which is convenient for moving at any time, preying on and avoiding enemies, and quickly swim away from the cave and swim into the deep water in case of disturbance. In the evening and at night, they come out to move and hunt, swim with their limbs pressed against their abdomen, and move forward by swinging their tails and torso to shoot the water. The salamander's tongue is round or oval, and the posterior end is not completely free, and cannot be turned out like a frog to feed. It is very fierce when predation, often waiting in the beach mouth rocks, found that the prey passed, suddenly opened its mouth to swallow, and then sent to the stomach to digest slowly, so in some places after the break said: "Baby fish sit at the mouth of the beach, like to eat their own food." Giant salamanders eat a large amount of food, including fish, frogs, crabs, snakes, shrimp, earthworms and aquatic insects, and sometimes birds and rats. As a result, giant salamanders play the role of top predators in freshwater ecosystems, at the top of the food chain, playing an important role in maintaining the stability and balance of ecosystems.
Due to the slow metabolism, when food is lacking, its hunger tolerance is very strong, and sometimes even giant salamanders will not starve to death without eating for 2-3 years. In the wild, giant salamanders gradually reduce their activity from September to October, and in winter, they hibernate in caves or large rocks in deep water, usually for up to 6 months, until march of the following year. However, it does not sleep deeply, and can still crawl and avoid when frightened. ▼▼▼
The giant salamander breeds from May to August each year, but its males and females are difficult to distinguish in appearance. During courtship, the male first swims around the female, sometimes forward, bending the tail forward and shaking rapidly, and sometimes swimming back, touching the female's body with the tip of the kiss, and this courtship game lasts for hours. Females can lay 400-1500 milky yellow eggs at a time, and form candidal bands ranging from several meters to tens of meters long, floating in the water. Fertilized eggs hatch at natural temperatures, and the incubation period is generally 30-40 days. The hatched larvae are shaped like tadpoles, with three dendrier-like gills on each side of the neck in front of the forelimbs, which are their respiratory organs, and the gills do not gradually disappear until the lungs are formed. Giant salamander larvae grow slowly and feed on plants up to 2 years of age.
Giant salamanders are exhibited in zoos and independent aquariums that have aquariums throughout China, and some have relatively large groups in some museums. ▼▼▼
However, although the wild population of giant salamander was once widely distributed in freshwater ecosystems such as the Yellow River Basin, the Yangtze River Basin and the Pearl River Basin in China, due to overfishing, river pollution, ecological environment damage and other factors, the wild population of giant salamander has decreased sharply. At present, China has strengthened the protection of giant salamanders by establishing nature reserves and vigorously eliminating poaching. At the same time, with the maturity of the artificial breeding technology of giant salamander, the scale of wild release of giant salamander has been expanding, which has played a positive role in the recovery of wild populations, and a certain scale of stocking populations has been formed in some places.
(All pictures of giant salamanders in this article are taken by the author Li Xiangtao)