There are many kinds of fish and each has its own characteristics.
However, when it comes to fish, many people have a common impression – “the memory of fish is only 7 seconds”.
In life, people often use “fish memory” to describe a person’s poor memory. So, is this really the case?
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In addition to fish, some friends will have such curiosity: fish live in water, will it drink water? Will you pee? How can fish live longer? Scroll down for the answer
Fish has only 7 seconds of memory?
It is widely circulated that fish have only 7 seconds of memory, but in fact fish have a memory of much more than 7 seconds.
In the 1960s, American scientists carried out research on fish memory on goldfish. The researchers fired a beam of light from one end of the tank to the other, and 20 seconds later delivered an electric shock at the other end of the tank, repeating the process multiple times. Subsequently, they found that goldfish formed a memory of the electric shock. When they saw the light again, they would quickly swim to the end of the light source to avoid the electric shock, and the goldfish could remember this “light” for up to a month. —Avoid” behavior pattern.
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For another ornamental fish, paradise fish, the researchers also found that they have a strong memory. They can remember “strange neighbors” they have seen before, and this memory can last for at least months.
In addition, many scholars take zebrafish, a model animal, as the research object, which further proves that fish have long-term memory. The researchers found that after training, zebrafish can learn to distinguish eating time according to the color of signal lights and how to walk mazes.
In fact, in life, we can also see the epitome of fish with long memory. Under the stimulation of tourists’ food, the ornamental fish in the scenic spot will actively swim to tourists whenever they approach the fish pond to try to get food. In addition, studies published in the journal Nature communication in recent years have found that zebrafish can also pass on memory to their offspring through DNA methylation (epigenetics).
Do fish drink water? Do fish pee?
According to the different living environment, fish can be divided into freshwater fish and marine fish, they all need to absorb enough oxygen from the water body to meet their own metabolic needs.
Fish mainly complete the respiration process through the coordinated action of the mouth, oropharynx cavity and operculum. During the process, a large amount of water will enter the fish from the mouth. This process can be simply defined as the process of the fish “drinking water”. Due to the great difference in the salinity of the water environment where freshwater fish and marine fish live, in order to maintain the stability of their own osmotic pressure, they have formed different ways of “drinking water”.
For freshwater fish, the salt concentration in the body is higher than that of the fresh water outside, so a large amount of fresh water will continuously penetrate into the fish body. It can be said that freshwater fish are “flooded” to drink water. In order to maintain the stability of its own osmotic pressure, freshwater fish needs to excrete a large amount of water infiltrated into the body. Its kidneys continuously excrete excess water and absorb salt, and finally excrete it through the bladder and cloaca.
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In contrast, seawater fish live in seawater, and the content of salt in their body is lower than that in the external seawater, resulting in the continuous loss of water in their body. In order to maintain the stability of osmotic pressure, seawater fish should take the initiative to “drink water” to supplement their reduced water. Seawater fish also need to excrete too much salt and metabolic waste from the body, and also need to urinate, but the urine output is much lower than that of freshwater fish.
Generally speaking, both seawater fish and freshwater fish “drink water”, but freshwater fish “drink water” passively, while seawater fish “drink water” actively. In addition, in the process of evolution, some fish have formed special ways to maintain the stability of their osmotic pressure. Shark, for example, can keep its osmotic pressure slightly higher than that of seawater by retaining urea. The metabolic waste in the shark body is mainly discharged through the skin. It has no bladder, so the shark does not “pee”.
How long does a fish live?
At present, more than 20000 kinds of fish have been found all over the world, and there are great differences in the lifespan of different kinds of fish.
The short-lived fish found so far include killifish, goby fish and silverfish. Although they don’t live and die like mayflies, they only experience about one year from birth to death. Peacock fish and zebrafish have a slightly longer life span and generally survive for about 2 years. The average life span of tilapia can reach 6 ~ 10 years.
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Sturgeon is a fish with a long sexual maturity cycle, and its life span can reach 40 years. For ordinary sharks, they can survive for 30 years, while whale sharks can live for 70 to 100 years.
Of course, there are fish that live longer than whale sharks, that is, pike. It can be called the “old longevity” of fish, and its life span can reach 200 years. The long life span of pike is related to its living in cold areas of the northern hemisphere.
What should we pay attention to when raising fish?
As the saying goes, raise water before raising fish, and the water quality is particularly important. The natural water used at home usually has a high chlorine content. Some ornamental fish are sensitive to chloride ions and may damage the gills of fish. Therefore, it is best to fully aerate or stand still for a few days before using natural water.
The supply of oxygen in water is also very necessary to prevent fish from dying due to hypoxia or long-term hypoxic stress. In addition, it is necessary to clean and replace the filter device regularly to ensure the cleanness of water quality.
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As fish is a kind of variable temperature animal, it is best not to exceed 1 / 3 when changing water each time, so as to ensure the relative stability of water temperature and prevent fish from “catching a cold”. Of course, adequate nutrition supply is also necessary, but we should pay attention to appropriate feeding. Too much residual bait will worsen the water quality.
In conclusion, clean and stable water quality and adequate nutrition supply are important guarantees for fish to live longer.
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