Greenland sleeping shark
Greenland sleeping shark is a kind of shark discovered only in modern times. They belong to large sharks, and the maximum length can reach 7 meters. Although they can't compete with the biggest shark whale shark, they are enough to challenge the great white shark.
Except for its size, Greenland sleeping sharks are similar in temperament to great white sharks. First of all, they are pure carnivores, which will kill any marine life smaller than themselves (medium and large, such as seals) and even carrion, so Greenland sleeping sharks are also called "crocodiles in the sea".
Greenland sleeping shark is a shark that lives in the northernmost part of the northern hemisphere. Although they are close relatives of the Pacific sleeping shark, there is no intersection between them. Moreover, sleeping sharks belong to a kind of cold water sharks. They either live in the cold ocean or in the deep sea at a depth of 2000 meters. Therefore, they were unknown for a long time.
Through the research of scientists, it is found that the natural enemies of Greenland sleeping sharks are only themselves and people, because Greenland people near Iceland have the habit of eating sleeping sharks and extracting cod liver oil from their livers, while Greenland sleeping sharks are cannibals. Their lack of natural enemies is related to their size, and the main reason is that their meat is poisonous. The meat of Greenland sleeping shark contains a lot of trimethylamine oxide, which is a neurotoxin. If eaten lightly, it will lead to diarrhea, vomiting, coma and even death. Therefore, the toxicity of meat is actually the reason why Greenland sleeping sharks have fewer natural enemies. Greenland sleeping sharks are immune to this toxin, so they can eat the same kind, and their meat can be cooked or dried at high temperature to weaken the toxicity. So Greenlanders will divide the meat of sleeping sharks and dry it before eating.
Age and life span of Greenland sleeping shark
From August 2065438 to August 2006, Science magazine published a paper about the latest discovery of sleeping sharks in Greenland. Scientists have dated the radioactive carbon of this shark population in Greenland and the Atlantic Ocean near Iceland, and found that this shark is a veritable "longevity star". Average age 156 years old, sexually mature and involved in reproduction. The average life expectancy is 272 years, which is the estimated maximum life expectancy. The publication of this paper has aroused widespread concern, and today, people's enthusiasm for sleeping sharks in Greenland is still unabated. Many friends may have questions: How is the age and life span of sleeping sharks measured?
In fact, at that time, scientists made great efforts to study the age of sleeping sharks in Greenland. Because the age of fish is usually judged by the calcification of tissues in the body. However, there is almost no calcification in the tissues of sleeping sharks, so this method cannot be used. Therefore, John Steffensen, a marine biologist at the University of Copenhagen in Denmark, decided to use the lens of Greenland sleeping shark's eyes for radiocarbon dating after asking for help from several scientists who specialize in dating.
After that, the research team captured 28 sleeping sharks. According to the survey, among the 28 sleeping sharks, the largest two are 4.93m and 5.02m respectively, and their corresponding ages are 335 and 392 years respectively. Together with the age of the other 26, the average age is calculated. Most sleeping sharks grow to 4 meters before reaching sexual maturity. There are two reasons for the inference that the sleeping shark is over 400 years old and the sexual maturity age is 156 years old. First, scientists found that the average annual growth length of sleeping sharks in Greenland is about 1-3 cm, so it takes about 150- 160 years to grow to 4 meters. Secondly, the largest Greenland sleeping shark found at present is 6.2 meters long, so its life span must be more than 400 years (5.02 meters, 392 years old).
Why can Greenland sleeping sharks live so long?
People are always interested in long-lived animals, and scientists are no exception, because if we solve the mystery of animal longevity, we may find the key to human longevity. To this end, the research team believes that there are three main reasons why Greenland sleeping sharks live longer:
First: living environment. Greenland sleeping sharks mainly inhabit cold seas, and the ambient water temperature is very low. As a fish that can't regulate its body temperature, the sleeping shark has a very low body temperature. Such a low body temperature means that the metabolic rate is much slower. When metabolism slows down, the aging speed of DNA will naturally slow down.
Second: moving speed. Exercise speed needs the support of two key factors: energy intake and metabolic rate. As animals at the top of the food chain in the ocean, most sharks swim very fast and are good hunters. But sleeping sharks in Greenland are different. Their swimming speed is so slow that we can catch them with our hands when we enter the water. It is such a slow moving speed that reduces its energy consumption and metabolic rate, so its longevity has a certain relationship with "slowness"
Having said that, many friends may have questions: How do sleeping sharks hunt when they move so slowly? This is actually related to a yellow and white parasite called long eyes, small eyes, small eyes and small eyes. This copepod parasite is parasitic on the eyes of sleeping sharks, which will eat part of the cornea of sleeping sharks and make them partially blind. However, it is also a luminous parasite. In the deep sea, this glow will attract some animals to sleep sharks, so sleeping sharks usually don't have to chase and hunt like other sharks.
Third: the growth rate is extremely slow. As a large fish with an average adult body length of about 5 meters, the sleeping shark has the slowest growth rate. They can only grow 1 cm a year, and their sexual maturity needs more than 1.5 years. Therefore, scientists believe that the longevity of sleeping sharks may be related to their extremely slow growth rate.
Of course, the secret of Greenland sleeping shark's longevity is still unknown, which needs further research by scientists. But from the current research situation, people can't learn to sleep sharks if they want to live a long life, because only the cold environment and extremely low body temperature can't be simulated by human beings.
abstract
Theoretically, the longest-lived animal in the world should be the lighthouse jellyfish, because as long as it has the ability of "rejuvenation", as long as it is not eaten or killed by natural enemies, it can theoretically achieve eternal life. Besides lighthouse jellyfish, the oldest animal is the Arctic clam. Scientists have previously captured an Arctic clam with a life span of 507 years in Icelandic waters, but unfortunately, this Arctic clam was put into the refrigerator and finally froze to death, with a life span of 507 years.
I believe everyone has found that these long-lived animals are not big. For example, the lighthouse jellyfish is only 5 mm in diameter, and the 500-year-old Arctic clam is a little bigger than the palm of its hand. The Greenland sleeping shark we talked about today, as a large vertebrate, can easily live to 300 or even 400 years old, which is really enviable. However, it is estimated that many people were discouraged when they saw the sexual maturity of 156.