What is the reproductive behavior of giant salamander?

The female salamander lays eggs from July to August every year, the eggs are laid in the rock cave, each tail lays more than 300 eggs, and the rest of the tending task is given to the male salamander. The male salamander curls his body into a semicircle and surrounds the eggs to avoid being washed away by water or suffering from enemy damage until the young salamander hatches after 2 weeks. After 15 days and 40 days, the young salamander is willing to leave after 15 days. The lifespan of giant salamander is also the longest among amphibians and can live as long as 130 years under the condition of artificial breeding.

Identification of male and female of giant salamander

The identification of male and female of giant salamander is mainly from the characteristics of cloaca, especially in the reproductive season. In the breeding season, the cloacal gland of the male giant salamander forms a full soybean petal, forming a raised longitudinal elliptical ring, which is very clear, which surrounds the cloacal pore, and there is an irregular fleshy protuberance on the outer edge of the cloacal foramen. The female reproductive foramen is mostly round, the pore diameter is relatively small, there is no white protuberance on both sides of the reproductive foramen, the outer edge of the foramen is smooth, and the inner edge can be seen that the cortex on both sides forms a prominent wrinkle to the cavity surface. In the non-breeding period, there is little difference in cloaca between male and female giant salamander, and it is not easy to distinguish. Dissecting the cloacal foramen, it was found that there was a pair of petaloid glands-cloacal glands under the skin of the male eminence, while there was a small amount of connective tissue around the female cloacal foramen. In the non-breeding period and immature giant salamander, there is no obvious bulge around the male cloacal foramen, while the cloacal gland is smaller, flat strip and does not form a ring. In addition, in terms of behavior, females are more stubborn and males are more docile in reproductive season.

Female-to-male ratio of giant salamander

Statistics of the sex ratio relationship during the breeding period, in a sense, can predict the reproductive capacity of giant salamander. According to the statistics of Bian Wei and others, the sex ratio of giant salamander is nearly equal under natural conditions, which is beneficial to the proliferation of natural resources. In addition, according to the Institute of Giant Salamander in Chenggu County, Shaanxi Province, it was found that there were slightly more males than females during the breeding period.

Gonadal development and annual cycle of giant salamander

Indicators of sexual maturity in Dazhou. After hatching, the giant salamander grows in the natural environment for five years, the body length is about 400mm, the weight is more than 360g, and the gonads are basically mature.

Relationship between fecundity and body weight of giant salamander

The giant salamander lays eggs once a year. The number of eggs directly determines the fecundity of giant salamander, the number of eggs is generally small, the number of eggs is closely related to age and nutritional conditions, and changes greatly. The results of Chenggu County Giant Salamander Research Institute showed that the giant salamander of 1.5~2.5kg carried 400 eggs. The results showed that the absolute fecundity of giant salamander increased with the increase of body weight, while the relative number of eggs decreased with the increase of body weight, and the relative fecundity of giant salamander weighing 615-1000g was the highest.

Reproductive behavior of giant salamander

According to the field observation, before the giant salamander spawned, the two parent mouths were bitten together. The male salamander took the initiative to bite the upper lip of the female salamander and the female salamander bit the lower lip of the male salamander. The two salamanders kept swinging in a straight line, swinging about 35 times / min, even if they were irradiated by electric light. After the sound or vibration separates it, it will bite immediately, and the body will twist violently at this time, which can last for 3 to 4 hours before it is released. There are no scars on the loosened lips, which can rule out the possibility of struggle and are initially identified as sexual behavior before spawning. Before spawning, the male salamander swims to the female habitat and chooses a tunnel-like cave with a water depth of about 1m, in which fresh water can flow from the mouth of the cave. The male salamander enters the cave and cleans the hole with the tail and head of the foot. Zhou Dinggang observed that when giant salamanders lay eggs, female salamanders adhere one end of the egg belt to attachments such as rocks or wood blocks, crawling while laying eggs. At this time, the male salamander goes to fertilize, wraps the egg band around its body to hatch, or stays in the hole to protect the fertilized egg. According to my observation, the giant salamander has the behavior of protecting eggs, and the parent salamander protects the eggs in the hole and comes out to attack as soon as they encounter the enemy, which is much more ferocious than usual. In the wild, it has been seen that the parent salamander around 1kg attacks individuals twice as large as it. If you use bait (frog or small fish) to fish outward during egg protection, the giant salamander will immediately release its mouth and will not be pulled out of the hole, which is completely different from the non-breeding season. Another parent salamander lives in a hole near spawning and sometimes protects eggs.

The hatching period of wild giant salamander eggs is 35-42 days, and the hatching date of eggs in the same nest is also different, but the difference is several days. At that time, the young salamander went into hibernation when it grew to 4~5cm. Dozens of young salamanders lived in groups in the same hole, and sometimes parent salamanders and young salamanders hibernated together.