Rare! Very beautiful! 丨Base construction

Review expert: Gu Mingdi Lian (He Lin), a well-known science blogger on mollusks on Zhihu

A few days ago, in a natural pond in Wuzhi Mountain, Hainan Province, some semi-transparent, coin-sized round creatures were found moving slowly in the water. These small creatures opened and closed, and there were many small tentacles of varying lengths around their bodies.

After further analysis by professionals, it was discovered that this round creature was actually the moon jellyfish , also known as the "giant panda in the water"!

Source: Weibo

What is the moon jellyfish? Why is it called the "giant panda in the water"? Is this little creature really as rare as a panda? Let's study this famous little animal together today.

"Giant Panda in the Water"

Everyone is familiar with jellyfish. Even if you have never seen a live jellyfish, you should have eaten delicious cold jellyfish on the table. In our understanding, there are jellyfish that can be used as cold dishes, and there are also beautiful ornamental jellyfish in aquariums, but these jellyfish live in the ocean. The peach blossom jellyfish we are talking about today is a very small number of Hydrozoa jellyfish in the jellyfish family that lives in fresh water.

Source: Baidu Encyclopedia

The peach jellyfish (Craspedacusta) belongs to the class Hydrozoa, the order Jellyfish, the family Craspedacusta. Hydrozoa are a primitive invertebrate that first appeared on Earth about 575 million years ago, much earlier than the appearance of dinosaurs.

Freshwater jellyfish, as the name suggests, are jellyfish that live in fresh water, but in fact some of their species also live in seawater or brackish waters.

The world's first scientific record of the peach jellyfish was in 1880, when the British ER Lankster discovered this freshwater jellyfish in a greenhouse tank in a botanical garden in a park called Regent in London. Zoologists at the time collected the first peach jellyfish as a specimen, which was later named Craspedacusta sowerbii.

The first recorded appearance of the peach blossom jellyfish in China was in 1907, when a Japanese collected the peach blossom jellyfish in the waters of the Yangtze River near Yichang. He named it the Yichang peach blossom jellyfish.

Source: Discussion on Several Issues of "Peach Blossom Jellyfish" by Xu Runlin

Biological Bulletin 2018

Later, peach jellyfish were also found in Sichuan, Guangxi, Zhongshan, Guangdong, and other places in my country, and even in Huairou Reservoir in Beijing. However, most of them are variants of Soler's peach jellyfish, and only the "Chinese peach jellyfish" found in Sichuan is a different species.

Although the first discovery of the peach blossom jellyfish in modern scientific history was in 1880, as early as the tenth year of Chunyou in the Southern Song Dynasty (1250), the literati Xiong Wenji described it in "Zhongzhou Peach Blossom Fish Records" as follows: "... I wondered if it was chasing the falling poplar flowers, but when I looked at it, I felt the stamens were wriggling, and floating in the water, leisurely and contentedly...", which clearly depicted the size and behavioral characteristics of the peach blossom jellyfish.

Source of Peach Blossom Jellyfish丨Wikipedia/OpenCage

The peach blossom jellyfish is called the "giant panda of the water" mainly because people think it is very rare, but in fact, the peach blossom jellyfish is not that rare. The reason why it is only occasionally seen in the news is mainly due to the differences in the growth and development status of its population in different environments.

The "two sides" of the peach jellyfish

The growth and development process of the moon jellyfish will show two morphological differences .

The swimming moon jellyfish we see are moon jellyfish in a mature state, which belongs to the jellyfish body .

The body of the moon jellyfish is very small, with a diameter of about two centimeters, about the same size as a coin. It is umbrella-shaped and crystal clear. There is a circle of shorter tentacles around its body, with many stinging cells distributed on it, which are used to anesthetize and hunt other small animals in the water.

Source: Baidu Encyclopedia

The jellyfish body is divided into male and female. During the breeding season, the fertilized eggs produced by the fertilization of male and female will develop into planktonic larvae. After the larvae mature, they sink and take root in the cracks on the bottom of the water and gradually develop and grow.

The peach blossom jellyfish rooted in the cracks looks like a small sea anemone, which is called the polyp stage of jellyfish. The polyp stage of peach blossom jellyfish has a very strong resistance to adversity and can endure all kinds of extreme environments such as severe cold and heat.

Therefore, if an aquatic environment becomes seriously polluted, the jellyfish body will die, but the polyp will still remain. They will fall into a dormant state and continue to develop after the environment recovers, and then produce jellyfish bodies through asexual reproduction.

That is to say, when the peach blossom jellyfish is in the medusae state and swimming in the water, it is small and transparent, difficult to find, and easy to die when the water is polluted, so people have an impression that it is a very rare "water panda". But those polyp peach blossom jellyfish actually stay there , and when the time is right, they can produce peach blossom jellyfish that can swim again.

Source: Song Daxiang; Zhang Chao; Wu Min, Peach Blossom Jellyfish, Biological Bulletin, 2002

The transformation from polyp to medusae has particularly high requirements for the environment and water quality . Therefore, the moon jellyfish is also known as the "aquatic ecological inspector" and "water quality identifier."

The discovery of the peach blossom jellyfish has enriched my country's species diversity, has high academic research value, and will help scientists conduct further in-depth research on the genetic evolution of species.

In the book "Red List of Chinese Species", the levels of various types of peach jellyfish are ranked, such as the Chinese peach jellyfish is a species of least concern, the Sichuan peach jellyfish is an endangered species, and so on.

In recent years, as the country attaches great importance to ecological environment protection, the frequency of discovering peach jellyfish in various places has also increased. If we find traces of peach jellyfish in the surrounding waters, please do not catch them by yourself . You need to report it to the local relevant departments in time, and let professionals protect it and do further testing. Protecting the environment starts with ourselves, so that our children and grandchildren can also see these beautiful creatures in nature in the future.

Finally, I want to say that although the moon jellyfish is beautiful, these small creatures in the water have nothing to do with "romantic luck". If you want to get rid of being single, you still have to work hard on your own.