How romantic is the underwater starry sky in "Gone Girl"? Would you watch it even if it cost you your life?

Recently, the movie "She's Missing", which has been jokingly called " the sweetest drama in the world " by netizens, is currently in theaters.

First there was "Let's go hiking together" in "The Bad Kids", and then there was "Let's go see the stars under the sea together" in "She's Gone". The two male protagonists redefined "vow of love" with their actions.

In the play, because Li Muzi loves Van Gogh's paintings, especially Vincent Van Gogh's "Starry Night", the male protagonist caters to her preferences and studies "Starry Night" to get close to her. The male protagonist is a gambler with no bottom line or principles. Li Muzi is planning to divorce because of her gambling debts, so the male protagonist kills Li Muzi when he wants to take her to see "Underwater Starry Night". The name of "Underwater Starry Night" is also related to Vincent Van Gogh's "Starry Night". The fish swimming in groups in the sea are like the image of the sky in Vincent Van Gogh's "Starry Night" . The whole story starts from this trip......

▲One of Vincent Van Gogh's masterpieces, "Starry Night"

▲The "undersea starry sky" in the movie "She Vanished"

Take you to see the underwater starry sky that you can only see once in a lifetime. It is extremely romantic and breathtakingly beautiful.

▲Promotional poster for the movie "Her Disappearance"

In movies, in the underwater tunnels of aquariums, or in documentaries about the deep sea, we can see groups of fish swimming around, just like the image of the sky in Vincent Van Gogh's "Starry Night". People are amazed and curious about why fish like to "group" and what is the biological significance of fish grouping behavior?

What is the biological significance of fish grouping behavior?

There are more than 20,000 recorded species of fish in the world. It is estimated that 25% of these fish live in groups throughout their lives, and 50% only live in groups when they are juveniles. These figures show that the phenomenon of fish grouping is quite common.

Scientists have used ships and airplanes to investigate the size of fish schools and found that most schools of mackerel in the Japanese Sea are composed of 50,000 to 100,000 individual fish. When a school of tens of thousands of mackerel appears, the water color appears purple-red or purple-black. The largest school of Pacific herring has 1 million to 3 million fish. Obviously, these schools of fish are very large. Biologists generally believe that grouping behavior is an adaptation that fish have retained after long-term natural selection, and it plays a very beneficial role in the survival of fish.

In biological terms, swarming behavior not only reduces the probability of bait fish being discovered by predator fish, but also reduces the probability of bait fish that have been discovered being successfully killed by predator fish. At first glance, a school of fish consisting of thousands or even tens of thousands of fish may be very conspicuous, but in fact, in the vast ocean, a school of fish is no easier to be discovered by predator fish than a single fish. The reason for this is largely related to the optical properties of the environment in which the school of fish is located.

▲The whirlpool of barracuda (Source: Visual China)

Due to the absorption and scattering of light by suspended particles in seawater, the visible distance of objects in water is very limited. Even in extremely clear water, the maximum visible distance of an object is only about 200 meters, and this distance has nothing to do with the size of the object. If there are 1,000 fish in a school, the probability of being discovered for one of them is only one thousandth of that for the 1,000 fish when they are scattered. It can be seen that the more individuals a school of fish consists of, the smaller the probability of an individual fish being discovered.

▲Dolphins capture a huge school of sardines (Source: Visual China)

In the long evolutionary process, in order to cope with the unfavorable environment of the sea with a lack of shelter, small fish in open waters follow one another and shield each other, thus forming groups. When they are attacked, the school of fish will become more dense. At this time, predatory fish may regard the dense school of small fish as a "monster", so that the chance of the small fish being attacked will be greatly reduced, and they will be safe even in danger. For a large number of small fish, "grouping" can increase the safety factor and ensure their survival and development in an environment where "big fish eat small fish". Grouping behavior also has various other functions in the lives of fish.

First, compared with individual fish, schools of fish have a stronger ability to resist adverse environmental changes. This collective resistance mechanism is determined by the mucus secreted by the fish's body surface. Clustering behavior can not only enhance the fish's resistance to toxins, but also reduce the fish's oxygen consumption.

From the perspective of hydrodynamics, fish swimming in groups can save energy consumption of individual fish, and the eddy energy generated by the swimming fish can be used by other fish following closely. Therefore, individual fish in the school can reduce a certain amount of swimming effort and continue to move forward.

Scientists have found that swarming behavior also has a certain adaptive significance in the process of fish migration. Even fish that usually live alone gather in groups when migrating. Fish that swarm together may be able to find the migration route faster because it is easier to find certain directional markers. The role of swarming behavior in spawning is also very obvious. Only when the same type of fish swarm in the same place can the eggs and sperm have a large enough chance to meet. In addition, many individual fish gather together to mate and lay eggs, which also plays a certain role in the spread of genetic factors.

Are all the fish in a school born from the same fish?

Although these fish look similar in size, they are not actually born from the same mother. Why? The reason is simple: either the fish's reproductive capacity is not that strong, or the survival rate is not that high . Let's take sardines as an example. The reproductive capacity of sardines is average among marine fish, and they lay an average of 50,000 to 60,000 eggs per year.

▲School of sardines (Source: Visual China)

Some of these eggs are eaten by other animals before they hatch, while others simply do not hatch due to environmental or internal factors. This results in a fish egg hatching rate of only 60% usually. Under artificial cultivation, it is already a remarkable rate of 80%. That is to say, according to the normal hatching rate, for a fish with reproductive capacity like sardines, at most only 40,000 or so can hatch successfully. This is still far from a school of hundreds of thousands of sardines, and the situation that the young fish are easily eaten by predators after hatching is not taken into account.

▲Sunfish (Photo source: Visual China)

In the ocean, the most fertile species is the sunfish, which can lay an average of 25 million eggs a year, and up to 300 million eggs. According to the hatching rate of fish eggs, it seems that "one mother can make a school of fish", but in fact, even fish with incredible fertility cannot do this, because less than one in a million sunfish can grow up normally, which is worse than sardines. Therefore, although the fish in a large school look similar, they are not born from the same fish.

What are the general classifications of fish schools?

Fish swarms can be generally divided into four categories according to their causes: reproductive, feeding, overwintering and temporary swarms. Reproductive swarms are swarms of fish formed by individuals with mature gonads. They are called reproductive swarms or spawning swarms. The structure of the swarms is generally: the body length is basically the same, the degree of gonad development is basically the same, but the age is not necessarily exactly the same. In addition, the density of reproductive fish swarms is relatively large, and they are also relatively concentrated and stable. Foraging swarms are swarms of fish that prey on the bait organisms they like according to their feeding habits. The fish in the foraging swarms have the same feeding habits. Generally speaking, the body lengths of the same species of fish with the same feeding habits are generally similar; different species of fish often gather together to feed on the same bait. Overwintering swarms are swarms of fish that gather together to find a new environment suitable for their lives due to changes in environmental temperature conditions. Fish that gather in the overwintering grounds may stop feeding or reduce feeding depending on their feeding habits and fatness. Temporary clustering When environmental conditions suddenly change or ferocious fish are encountered, the temporary concentration of fish is called temporary clustering. In particular, when the temperature and salinity gradients change sharply or when there are a large number of organisms that fish cannot eat or swallow, resulting in the appearance of ferocious fish, fish often gather temporarily. When environmental conditions return to normal, they may disperse and live normally again.

(Compiled by Duan David, content references: Journal of Natural Resources, Procuratorate Daily, "Science Popularization Qingdao" WeChat public account, etc.)