Information about Chinese alligator

China alias: China catfish, earth dragon and pig dragon.

Latin scientific name: Chinese alligator

English name: Chinese Auigator

Siluridae; Alligator family

classify

Boundary: animals in the animal kingdom

Door: Chordata, Chordata.

Class: reptile sauropod

Objective: Crocodiles

Family: Alligator.

Genus: alligator.

Species: Chinese alligator

The Chinese alligator, or catfish, is a kind of alligator unique to China, commonly known as the pig-woman dragon and the earth-dragon, and it is also one of the smallest crocodile species in the world. Mainly distributed in the middle and lower reaches of the Yangtze River. It is not only ancient, but also an endangered reptile in the world. Many features of dinosaurs and reptiles can still be found in Chinese alligators. Therefore, people call the Chinese alligator a "living fossil". Therefore, alligator sinensis is of great significance for people to study the rise and fall of ancient reptiles and the evolution of paleogeology and biology. China has listed the Chinese alligator as a national first-class protected animal, and killing is strictly prohibited. In order to keep the competition of this precious animal going, China has also established nature reserves and farms for artificially raising Chinese alligators in Anhui and Zhejiang. In 1970s, it was taken abroad and traveled around Europe, and became famous all over the world.

Appearance characteristics

The Chinese alligator is similar to the Mihe alligator, but much smaller. The adult Chinese alligator rarely exceeds 2. 1 m, but generally only 1.5 m. Not as big as African crocodiles and Thai crocodiles. The Chinese alligator has a short and blunt kiss, which is a kind of alligator. Because the Chinese alligator looks like a dragon, it is commonly called "earth dragon" or "pig female dragon". It weighs about 36 kilograms. Their heads are bigger and their scales have more granular and banded lines.

The whole body is clearly divided, including head, neck, trunk, limbs and tail. The whole body skin is cortical, covered with a cortical deck, and the abdominal deck is higher. The back is dark brown or dark yellow, the abdomen is gray, the tail is long and flat, and there are gray-black or gray-yellow surgical lines. Its tail is a weapon for self-defense and attacking the enemy, and it also plays a role in pushing the body forward in the water. The limbs are short and powerful, and there are obvious differences between a pair of forelimbs and a pair of hind limbs: the forelimbs have five fingers without webbed fingers; The hind limbs have four toes, and there are webbed toes between them. These structural features are suitable for it to live in water and land.

The tail is about the same length as the body length. The head is flat, the nose and mouth are long, and the external nostril is located in the nose and mouth with a flap. The body is covered with a piece of leather armor, and the abdominal armor is soft; The nail plates are nearly rectangular and neatly arranged; There are two rows of nail plates protruding to form two ridges running through the whole body. The limbs are short and thick, with webbed toes and claws. The back of the body is grayish brown, the front of the abdomen is gray, and it is grayish yellow from the anus to the back. Flat tail. Newborn crocodiles are black with yellow stripes.

Alligator's kiss is short and round, with a pair of nostrils in front. Interestingly, its nostrils have valves that can be opened and closed. Eyes are all black, with eyelids and membranes, so Chinese alligator's eyes can be opened and closed.

distribution range

Mainly distributed in parts of Anhui, Zhejiang, Jiangxi and other places.

living environment

Chinese alligators live in fresh water and like to inhabit lakes, swampy beaches or wet areas with weeds and absinthe on hillsides and streams. It has superb ability to dig holes in buildings. Its head, tail, pointed toes and claws are the tools for digging holes in buildings. As the saying goes, "There are three caves for cunning rabbits", but there are more than three caves for Chinese alligators. There are often several holes in its caves, some are overgrown with reeds and bamboo forests on the beach, some are at the bottom of the pond, there are entrances and exits and vents on the ground, and there are also side holes adapted to various water levels. The cave twists and turns, criss-crossing, like an underground maze. Perhaps it was this underground maze that helped them survive the cold ice age and the cold winter, and also helped them escape from the enemy and survive. Fish, frogs, snails and mussels are used as food. But sometimes it attacks poultry and crushes crops. Coupled with the "ugly" appearance, it has long been regarded as a harmful animal, so the number is scarce.

Growth and reproduction

Mating in June, laying eggs in July and August, each nest can lay more than 20 eggs. The eggs are laid in the grass, covered with weeds, and the female crocodiles are guarded by them and hatch at natural temperature. The incubation period is about 60 days, and young crocodiles are hatched in September. Have the habit of hibernating.

Chinese alligator is a unique species in China, and it is difficult to breed under artificial feeding conditions. Under good environment and careful feeding conditions, the Chinese alligator gave birth to the first batch of young crocodiles in China in 1980, which became a precedent for successful reproduction under artificial feeding conditions. At present, the crocodile family lives quietly and comfortably in this environment, and its population is growing.

Living habits

Some people call the Chinese alligator a crocodile and treat it as an aquatic animal such as fish. In fact, Chinese alligators have no gills and are not aquatic animals. It's just that the Chinese alligator has returned to the water, formed some characteristics to adapt to life in the water, and has the amphibious ability. In this way, the Chinese alligator has expanded its life field and easily became the winner in struggle for existence.

Chinese alligators dig holes in rivers, lakes and ponds. It is fierce and feeds on all kinds of animals, birds, reptiles, amphibians and crustaceans. Mating in June, laying eggs in July and August, each nest can lay more than 20 eggs. The eggs are laid in the grass, covered with weeds, and the female crocodiles stay by and hatch at natural temperature. The incubation period is about 60 days. He has the habit of hibernating. He went into the cave to hibernate from June to October every year in 5438 and didn't come out until April and May of the following year.

Chinese alligators are quiet. They often live in caves during the day and go out for food at night. However, it also comes out during the day, and especially likes sunbathing on the shore and beach near the cave. It often closes its eyes, crawls motionless, and is in a state of semi-sleep, giving people the illusion of being slow. However, once it encounters the enemy's injury or finds food, it will immediately swing its thick tail from side to side and quickly sink to the bottom of the water to avoid the enemy's injury or chase food. Its favorite foods are snails, mussels, small fish, shrimps, waterfowl, rabbits, water snakes and other animals. Chinese alligator eats a lot and can store a lot of absorbed nutrients in its body, so it has strong hunger tolerance and can spend a long hibernation period.

Unique predation method

Chinese alligators can jump up and catch when they encounter enemy injuries or hunt for food on land. When it can't catch it vertically, its huge tail can wave violently. Unfortunately, although the Chinese alligator has seemingly sharp teeth, it is slotted. This kind of tooth can't bite and chew food, but can only "clip" the food like pliers and swallow it. Therefore, when catching large terrestrial animals, Chinese alligators can't kill them, but drag them into the water and drown them; On the contrary, when Chinese alligators catch large aquatic animals, they will throw them on land, causing their prey to die of lack of oxygen. When a large piece of food can't be swallowed, the Chinese alligator often slaps the food on a stone or tree trunk with its big mouth until the food becomes soft or broken, and then swallows it with its mouth open. If not, it throws its prey aside and lets it rot naturally until it can be swallowed. Chinese alligators also have a special stomach. This stomach is not only rich in gastric acid but also high in acidity, so its digestive function is particularly good.

Demographic situation

/kloc-In the 9th century, Chinese alligators were found in the lower reaches of the Yangtze River, Hubei, Anhui, Jiangxi and Jiangsu. They like to dig holes and build caves in the shallows of hills, streams and lakes, but this reptile can't survive without water. It is clumsy and slow on land, but once in the water, it is like a duck to water. This amphibious feature led to the tragic fate of the Chinese alligator. Most of the shallows where Chinese alligators built caves were reclaimed as farmland, and most of the vegetation on the mountains was destroyed. The water storage in the mountains is greatly reduced, and droughts and floods are frequent, forcing Chinese alligators to leave their caves and look for suitable habitats everywhere. This migration process created opportunities for natural death and man-made hunting. Over the years, the Chinese alligator has been hunted, its caves have been destroyed and its eggs have been broken or taken away. The use of chemical fertilizers and pesticides has also greatly reduced the number of aquatic animals, the main food of Chinese alligators. At present, the distribution of alligator sinensis has been reduced to a narrow area at the junction of Jiangxi, Anhui and Zhejiang provinces.

Many conservation work began in the 1970s. 1979 Anhui Xuancheng alligator breeding research center was established, 1980 alligator nature reserve was established. At the same time, our people have also carried out a series of protection actions to increase the number of Chinese alligators. 1983 census found that there were only 500 wild Chinese alligators. 1992 census found that the number of wild Chinese alligators increased to 900. The Chinese alligator breeding research center has made great achievements, with 7,000 young crocodiles hatched in recent years. This is very gratifying. The great success of artificial breeding has created conditions for the recovery of the number of Chinese alligators.

At present, there are more than 10000 captive Chinese alligators in China, mainly distributed in China Chinese alligator breeding center in Xuancheng, Anhui Province, and many zoos. Since 1970s, scientists in China have embarked on a bumpy journey of artificial breeding of alligators. At present, China's technology of artificially incubating crocodile eggs and artificially raising crocodiles has been at the forefront of the world. Thanks to their unremitting efforts, the number of Chinese alligators has increased from 170 in the early days of the farm construction to more than 4,000 now, and the annual breeding number exceeds 1000. Chinese alligator became the first endangered animal approved by international trade conventions for commercial development and utilization.

Protection level

Chinese alligator is a national first-class protected animal in China, which is listed in CITES Appendix I, while IUCN is listed as extremely endangered.

1979 A Chinese alligator farm was established in Xiajiadu, Xuanzhou, and artificial feeding was studied. 1982 to establish the Chinese alligator nature reserve, 1983 to establish the Chinese alligator breeding research center in the reserve, with an investment of10.7 million yuan to build 8 small-scale breeding ponds with an annual breeding pond of 65,438+. After several years of experiments, it was basically successful, the survival rate of artificial incubation reached 95.4%, and more than 2,000 young crocodiles were bred, which won the National Natural Science Award.

related data

The Chinese alligator, also known as the giant salamander, was called the giant salamander in ancient times, which was recorded as early as Oracle Bone Inscriptions in Shang Dynasty. The ancients often thought that giant salamander was a kind of dragon. Li Shizhen's Compendium of Materia Medica called the Chinese alligator Jilong. People generally call it earth dragon, pig female dragon. In a word, Chinese alligators were regarded as "dragons" in ancient times.

Chinese alligator is an amphibious reptile, which likes to inhabit sparsely populated rivers, lakes and ponds. It is mostly active at night and feeds on small animals, such as fish, shrimp, mice, mussels and birds. It has a strong ability to endure hunger and can go without eating for months.

People often use "crocodile tears" as a metaphor for hypocritical people. Because people often see Chinese alligator eating some small animals with tears, as if it can't bear to eat. So what happened to crocodile's tears? Its tears are not out of pity, but because the excess salt in its body is mainly secreted by a special gland, which is next to its eyes, which makes people mistakenly think that the salty liquid secreted by this gland is its tears. When it eats, its glands are just secreting salty liquid, so people often think that it is crocodile tears for these small animals to eat.

Chinese alligators have the habit of hibernating. Because their habitats are cold in winter and the temperature is below 0℃, they have to hide in caves to hibernate. It is observed that 10 hibernates from the end of June to the middle of April of the following year, which means that the Chinese alligator hibernates for half a year. The cave where it hibernates is a bit unusual. The cave is two meters deep from the ground, and the structure in the cave is complex, with holes, tunnels, bedrooms, beds, pools and air pumps. Lying on the platform is where the Chinese alligator lies. In the coldest season, the temperature of the platform is about 65438 00℃. It must be very comfortable for the Chinese alligator to hibernate in such an advanced cave. At the beginning and end of hibernation, it does not fall asleep deeply and can respond to stimuli. After a long time, I fell asleep, like dead, and I couldn't see its breathing phenomenon.

The Chinese alligator, who just woke up from hibernation, must first go all out to feed. At this time, it was late spring outside the cave. Before long, the fully recovered Chinese alligator began to make different courtship calls. The loud cry of the male crocodile could be heard hundreds of meters away, but the low cry of the female crocodile could be heard. With the sound of the phone as a signal, they gradually narrowed the distance and got together. At this time, it is about the beginning of June. Chinese alligators mate in water and fertilize in the body. At the beginning of July, female crocodiles began to build round nests with weeds, dead branches and soil in suitable places for spawning, and each nest laid about 10 ~ 30 eggs. Eggs are grayish white, slightly larger than eggs. Eggs are covered with thick grass, which is the hottest season in summer. Soon, some nest materials and thick grass rot and ferment in the hot sun, releasing heat, which is used by crocodile eggs to hatch. During the incubation period, female crocodiles often come to guard their nests. About two months later, when the female crocodiles hear the cries of the young crocodiles at the edge of the nest, they will immediately pull out the grass covering the young crocodiles, help them climb out of the nest and lead them into the pool. Young crocodiles have orange stripes on their body surface, which are very bright in color, which is obviously different from adult crocodiles.

It should be noted that in the Chinese alligator population, males are a minority and females are an absolute majority, and the ratio of male to female is about 5∶ 1. What is the reason? This is an interesting natural law. Zoologists have found that the fertilized eggs of pure alligators have no fixed sex when they are fertilized. Two weeks after the fertilized egg is formed, its sex is determined by the incubation temperature at that time. The young crocodiles hatched below 30℃ are all males, while those hatched above 34℃ are all males, while those hatched between 3 1 ~ 33℃ are mostly females, with few males. When the incubation temperature is lower than 26℃ or higher than 36℃, Chinese alligator cannot hatch, and most fertilized eggs of Chinese alligator hatch at suitable temperature.

Anhui alligator national nature reserve

Anhui alligator national nature reserve is located in Xuancheng, Anhui Province, covering an area of 44,300 hectares. 1975 was established as a provincial nature reserve, and 1986 was promoted to a national level. The main object of protection is the Chinese alligator and its ecological environment.

The reserve is located in the transitional zone between Jiangnan ancient land and Jinling sag. The climate is warm, the rainfall is abundant, the terrain is complicated, and gullies, ponds, canals and dams are scattered all over the place. In ponds, gullies, gullies and reservoirs below 300 meters above sea level, the Chinese alligator, the oldest reptile endemic to China, lives. Chinese alligator and American Mississippi alligator are the only two kinds of freshwater crocodiles in the world, and their numbers are extremely rare, so they are listed as first-class protected animals by the state. Since the establishment of the nature reserve, the population of Chinese alligator has greatly increased through the combination of in-situ protection and artificial reproduction, which has initially lifted the danger of extinction of this species.

Research progress of alligator sinensis

As early as 3,000 years ago, the Chinese alligator was recorded in Oracle Bone Inscriptions, China, but it was not until 1879 that Fauville named it Chinese alligator and made it public. The study of Chinese alligator began in 1970s, and remarkable achievements were made in ecology, histology and embryology of Chinese alligator in 1980s and 1990s. The whole research process can be roughly divided into two periods.

1. Study on saving the Chinese alligator species (1982 ~ 1992)

Due to the destruction of the ecological environment, the number of Chinese alligators has dropped sharply. 1973 international wildlife conservation conference listed it as an endangered species and a prohibited species. 198 1 year The results of a joint survey by Chinese and American scientists show that there are only 300 ~ 500 wild Chinese alligators. In order to save the Chinese alligator, the government of China invested and built the Chinese alligator breeding research center in Xuancheng, Anhui Province on 1982. At the same time, some scholars have carried out extensive research on the population distribution, quantity, habitat, feeding habits, reproduction, hibernation, caves and activity rules of Chinese alligator. Chen and his colleagues made a systematic study on the population quantity and distribution, morphology and ecology of Chinese alligator, and published the monograph "Chinese alligator" on 1985. Although the Chinese alligator was successfully hatched as early as 1976, the problem of egg yolk induration caused a large number of Chinese alligators to die in the process of artificial feeding (still unsolved). Chen et al. (1989) analyzed the field ecological conditions of young crocodiles after birth, measured the energy metabolism of young crocodiles, and calculated the time required for young crocodiles to digest all the yolk in their bodies. It was found that feeding young crocodiles too early after hatching was the reason why young crocodiles' yolk was difficult to digest and formed induration. The measures taken are as follows: firstly, the incubation temperature of young crocodiles is raised to 365,438+0 ~ 32℃ to speed up the absorption of yolk of young crocodiles; The second is to postpone the feeding time to 18 ~ 20 days after the young crocodiles hatch, so that the yolk can be completely absorbed. At the same time, it was found that the humidity was above 95% 20 days before hatching and decreased to about 90% 20 days later, which could improve the hatching rate and eliminate the swelling of hatched eggs. 1987 The hatching rate of Chinese alligator was over 95%, while the mortality rate of young alligator was only 2. 1%( 1982 the mortality rate of young alligator was 40%). The viscous substance outside the Chinese alligator eggshell is of great ecological significance to prevent the egg from dehydration and excessive external water from entering the egg. If the sticky substance is destroyed, the hatching rate will decrease. Pan Jihong et al. (1988) found that some young crocodiles died of liver diseases caused by Proteus, or from the combined infection of Citrobacter, Pseudomonas and Proteus with the lungs. Recently, Wang Renping of the Chinese alligator breeding research center found a large number of nematodes in the gastrointestinal tract of dead young crocodiles. Therefore, nematode infection may also be one of the causes of the death of young crocodiles.

After 10 years of research and efforts, the hatching rate and survival rate of young crocodiles have been kept above 95%, and the population has increased greatly, which not only saved the Chinese alligator, but also created conditions for its development and utilization. 1992 At the International Trade Conference on Endangered Animals and Plants held in Kyoto, Japan, the Chinese alligator was approved for commercial reproduction and commercial development. According to the investigation in Li Chengyuan, by the end of 1994, there were about 667 ~ 740 wild crocodiles in the 83 000 hm2 Chinese alligator reserve. There are 4376 artificial crocodiles in the Chinese alligator breeding research center, and the number of crocodiles has exceeded 7000 by the end of 1997.

2. Basic theoretical research on histology, embryology and physiology of alligator sinensis (late 1980s to present).

The scales of alligator sinensis are similar to dermal scales in nature, and the formation mode is similar to the appearance of bird feathers. There are three kinds of skin glands; Dorsal gland, cloacal musk gland and mandibular gland. The dorsal gland is only symmetrically distributed under the second row of scales on the left and right sides of the dorsal midline of embryos or young crocodiles, and then asymmetrically degenerates, and asymmetrically distributed in adults, so it is a degenerated organ. Cloacal musk deer gland and mandibular gland are both secretory glands, and their functions are related to mating and reproduction. Tongue glands of alligator sinensis can be divided into two types: simple single-tube glands and complex multiple-tube vesicular glands, which are mainly distributed on both sides of the tip of the tongue and the lamina propria of the dorsal midline of the tongue, and have the functions of lubricating food and excreting sodium chloride. Continuous low temperature incubation will inhibit the development or prevent the formation of tongue glands. The taste buds of adult Chinese alligators are concentrated in the middle of the tongue, but in the embryonic stage, they begin to appear on the 48th day after hatching. Besides the tip of the tongue, there are taste buds at different developmental stages on the tongue surface, which may also be a degeneration phenomenon. The esophageal epithelium of alligator sinensis is stratified columnar ciliated epithelium, and the epithelial surface cells are composed of columnar ciliated cells and goblet cells, which are similar to birds. The goblet cells appeared in the gastric epithelium of alligator sinensis during embryonic period, and then died. There are two kinds of gastric glands, the cardia gland and pyloric gland are single-tube glands (a few of them have branches), and the fundus gland is branched tubular glands, both of which are formed by the invagination of gastric epithelium to lamina propria in embryonic stage. Histochemical studies show that cardiac gland and pyloric gland are mainly composed of mucus cells, but there may also be parietal cells and main cells at the bottom of glandular duct. The composition of gastric fundus gland cells is similar to that of mammals. Compared with mammals, the intestinal wall of Chinese alligator lacks muscularis mucosa, villi protrude from lamina propria into intestinal cavity or droop directly from epithelium into lamina propria, and small intestinal glands are mainly distributed in the anterior segment of duodenum. On the 52nd day, obvious goblet cells appeared in villous epithelium of small intestine and plica epithelium of large intestine. The ultrastructure and formation of liver and pancreas cells in alligator sinensis are basically the same as those in birds and chickens. In the respiratory system of Chinese alligator, there are three kinds of cells in trachea and bronchial mucosa: ciliated cells, mucus cells and basal cells. However, in the embryonic stage, the epithelium of trachea and bronchus can only be divided into light cells and dark cells, and ciliated cells and mucus cells may be formed after hatching. However, on the 46 th day of culture, ciliated cells in lung epithelium formed obviously. The tissue structure and formation process of lung epithelial type ⅰ and ⅱ cells and larynx are similar to those of mammals. The author recently studied the peripheral blood of alligator embryos and found that the types and morphology of blood cells can be clearly divided into two periods. The proportion of immature cells in various blood cells is large before the 40th day of incubation and small after 40 days, which is consistent with the formation of bone marrow before the 40th day of incubation. The kidney structure of alligator sinensis is similar to other reptiles, but the epithelial cells of proximal convoluted tubule and collecting duct have no endoplasmic folds, and the epithelial cells of distal convoluted tubule have a few endoplasmic folds, which is consistent with their fresh water life. The Chinese alligator has a developed sense of smell, a large nasal cavity, a more complex structure such as turbinate than other reptiles, and a corresponding increase in the number of olfactory cells. The inner ear structure of Chinese alligator is very similar to that of birds, and the development of the three semicircular canals has a certain order. Compared with other crocodiles, the sphincter in iris and the ciliary muscle in ciliary body belong to striated muscles, and the mitochondrial crest in the oval of visual cells is parallel to the long axis of mitochondria. The regularity of retinal stratification of alligator sinensis embryos and the differentiation process of cone cells and rod cells are similar to those of reptiles lizards and skinks. The blood sugar level of Chinese alligator usually remains near the reference level108.75 23.5 mg/100 ml, but there is obvious seasonal change, which is related to the seasonal change of temperature.

To sum up, the organizational structure characteristics and physiological changes of Chinese alligator are adapted to living habits and living environment. For example, developed sense of smell, vision and hearing adapt to land predation and nesting; The special lung cavity structure and taste bud structure have the characteristics of adapting to aquatic life; The seasonal change of blood sugar concentration is adapted to the periodic alternation of hibernation, activity or reproduction of Chinese alligator. The embryological study of alligator sinensis provides useful enlightenment and evidence for discussing the systematic evolution of alligator sinensis and confirming its taxonomic status. For example, goblet cells appeared in the gastric epithelium of alligator sinensis in the early embryonic stage, indicating that alligator sinensis is far from a lower amphibian; The formation of scales and throat cavity also shows that Chinese alligator is similar to birds and mammals. The appearance and degeneration of dorsal glands further confirmed that Chinese alligator and Mihe alligator are closely related, and they have the same ancestor, but adult Mihe alligator still has bilateral symmetrical dorsal glands. Based on this, it is speculated that Chinese alligator may have a higher taxonomic status than Mihe alligator, or Mihe alligator is an older crocodile than Chinese alligator.

Of course, the study of Chinese alligator needs to be broadened and deepened. Although the meat of Chinese alligator has become a crude product "Chinese alligator floss", the first pair of leather shoes made of Chinese alligator skin has quietly come out, but this is only the beginning of the development and utilization of Chinese alligator. In order to further develop and utilize the Chinese alligator, we must solve a series of problems in its large-scale reproduction and breeding. Chinese alligator has a special evolutionary position. At present, there are different opinions on how to classify and belong, and the sex determination mechanism of Chinese alligator is also attracting attention. It seems difficult to determine such problems only from the histological level, and it is urgent to carry out in-depth research in histochemistry and molecular biology.

Research process and conclusion

In 2003, a one-year special study was conducted in Anhui alligator nature reserve. During the monitoring process, the date, time, quantity and weather of Chinese alligator were recorded. Chinese alligator began to growl in March every year, and stopped growling in 165438+ 10. There was a significant difference in the number of Chinese alligators' howls in different months (χ2 test: χ 2 = 448.29, DF = 8, P < 0.0 1), among which the number of Chinese alligators' howls was the highest in June, accounting for 26.0% of the whole year. The howling frequency of Chinese alligator in breeding period (June-September) was significantly higher than that in non-breeding period (Mann-Whitney U test: u = 2.0, P < 0.05). There are significant differences in the times of Chinese alligator's roar at different times of the day (χ 2 = 233. 18, DF = 17, P < 0.0 1), and there is an obvious roar peak, which is more in the daytime than in the evening (U = 12.5, P

On April 27th, 2003, two female and one male artificially bred healthy adult Chinese alligators (referred to as Chinese alligators) were released to the Red Star Chinese alligator reserve in Xuancheng, Anhui Province, and their activity areas were measured by radio telemetry within four weeks after the first release, and a total of 372 loci were recorded. Their activities are also observed by telescopes during the day and by light counting at night. The results showed that three Chinese alligators were in different stable regions after 3 ~ 14 days, which had domain characteristics. The activity area of male is larger than that of female, and the change of daily activity area is also larger than that of female. The local environment is often close to the coast with dense vegetation.

According to 150 Chinese alligator embryos with different gestational ages, the embryonic development process of Chinese alligator was divided into 28 stages. Early embryos are mainly divided into body segments, body bends, brain vesicles, sensory organs, appendages, branchial arches, facial processes, heart, skin and other external forms. The staging of late embryos is mainly based on histological indexes of organ development. It was found that the gestational age of the first 20 cycles was very consistent with that of the Chinese alligator Mihe, and the gestational age of the last 8 cycles was different from that of the Chinese alligator Mihe. It is considered that the staging of late crocodile embryos should be based on the histological indexes of organ development, so that the embryo development of different crocodiles has the same staging standard, which provides basic data for the follow-up study of crocodile developmental biology.

Three Chinese alligator blood samples were collected from Xuancheng Chinese alligator Breeding Research Center, Anhui Province, and a pair of degenerate primers were used to amplify some fragments of the second foreign element of MHC Ⅱ B gene. By cloning, single strand conformation polymorphism analysis and sequencing, the determined sequence was compared with the downloaded eight MHC sequences to determine the sequence differences and mutation sites. Results A total of 10 different sequences were obtained, and the fragment length was 166bp. There are 38 mutation sites in nucleotide sequence and 23 mutation sites in amino acid sequence. The estimated non-synonymous substitution (dN) of antigen binding sites is significantly higher than that of synonymous substitution (DS). The NJ tree with 10 sequence is very similar to the MP tree. Both branches are A and B, and there are 9 nucleotide sequences and 7 specific amino acid sequences in both branches, which indicates that the second exon of MHC Ⅱ B gene in Chinese alligator is highly polymorphic, which is beneficial to the genetic protection of Chinese alligator breeding population.

From June 1999 to July 10, 2002, 40 wild Chinese alligator caves were discovered in Anhui Chinese alligator national nature reserve (currently 24 caves were abandoned on 16). Five environmental variables such as cave direction, concealment degree, height from water surface, distance from water source and distance from village were measured. The results show that 87.5% of the caves are located 0-0.5 m and < 0 m above the water surface, 85.0% of the caves are less than 5 m away from the water source, 32.5% of the caves face north, and 72.5% of the caves face north. The contribution rate of the principal components of the height from the water surface, the distance from the water source, the direction of the hole and the degree of concealment decreased in turn, reaching 76.6%. Convenient water intake is the main factor in selecting drilling location.