Turtles and tortoises are a very old and extremely prosperous order among reptiles, and the fossil records of their ancestors can be traced back to the 220 million-year-old half-toothed turtle found in Guizhou, China. Turtles and tortoises originated earlier than crocodiles and scaly orders, survived several mass extinctions, and there are still nearly 350 species in 14 families, in addition to the cold and high latitudes and extremely arid regions, almost all over the world's tropical and temperate regions, is a very common fauna.
On the left is the suborder Traverse, and on the right is the suborder Lateral-necked turtle
Turtles and tortoises are divided into two suborders – the suborder Leptocere and the lateral-necked turtle suborder. The suborder Tortoises have curved neck bones when they retract their heads back into their shells, while the suborder Lateral-necked turtles coil their heads outside the shell. However, there are some species of tortoises that cannot retract their heads into their shells, such as hawk-billed turtles and sea turtles.
According to the habits of life, turtles and turtles can be roughly divided into water turtles, tortoises and semi-aquatic turtles.
According to the softness of the shell, the hard-shelled one is usually called the turtle, and the soft-shelled one is called turtle and shrew.
But there is one turtle that is very special, it does not have a hard shell, but it does not look like turtles and shrews, and it also lives in the ocean, it is the Leatherback Turtle, the largest turtle turtle in existence. But the leatherback turtle is more special than that, and today I will talk about this magical giant turtle.
<h1 class="pgc-h-arrow-right" > overview of leatherback turtles</h1>
There are 7 species of sea turtles in existence, from small to large, olive ridley, Kemp'Ridley, Hawkbill turtle, flatback turtle, green turtle, loggerhead, leatherback turtle. The first 6 species are all turtles, and only the leatherback turtle belongs to a separate leatherback turtle family. The appearance of the leatherback turtle is indeed very different from the other 6 species of sea turtles.
Comparison of leatherback turtles with 6 other species of sea turtles
The dorsal carapace of the 6 species of turtles in the family Turtles is oval or nearly round, with 3 rows of shields arranged on the dorsal carapace, and a smaller shield around the periphery, under which is an extremely hard dorsal carapace formed by the overgrowth of the dermal bone between the ribs, vertebrae and ribs. The dorsal carapace is brown, reddish brown, olive green, orange or olive grey in color.
The appearance of the leatherback turtle is much more simple, the body color is dark black or dark blue, and it is scattered with white spots. The back is thin, tough, ossified skin, supported by a skeleton of vertebrae and ribs, like a leathery shield. On the dorsal carapace, seven ridges running longitudinally through the dorsal carapace are arranged from the body to the back. The ventral oracle is incompletely ossified and has 5 longitudinal ridges. The name "leatherback turtle" comes from the cortical dorsal carapace and these 7 ridges.
Leatherback turtle skeleton
Because its leathery dorsal carapace is very flexible, it is called a leather turtle; because of its migratory habits like a swallow punctuality or a huge forelimb like a swallow's wings, it is also called a swallow turtle; because its dorsal carapace is very similar to the European rute, it is called a rut turtle in Europe; fishermen on the southeast coast of China think that its back carapace resembles a starfruit, called a starfruit turtle.
The most impressive thing about the leatherback turtle is its "demon abyss" large mouth, which is open and full of sharp horned thorns with a strong visual impact. Leatherback turtles have no teeth, their beaks are underdeveloped, they eat almost by inhalation, and then rely on the barbs densely packed in the mouth and esophagus to tear their prey apart and prevent the prey from escaping, acting like a conveyor belt to transport food in the esophagus. The main food of the leatherback turtle is cephalopods, sea squirts and sponges, and the favorite food is jellyfish, but this also brings great pain to the leatherback turtle. Marine pollution has increased, countless plastic bags floating in the sea, and after being eaten by leatherback turtles, they cannot be excreted due to barbs, which will block the esophagus and cause them to die, which has happened many times.
On September 19, 2017, a leatherback turtle weighing 2 meters and weighing 700 kilograms appeared on the beach of Haicarea in Catalonia, Spain, and was found dead, because of accidental ingestion of plastic waste.
Turtles are a symbol of longevity in people's minds, but most turtles have a lifespan of 30-50 years, which is a long life expectancy compared with the ancients. Leatherback turtles can live longer than 60 years, which is a moderate level among turtles.
<h1 class="pgc-h-arrow-right" > leatherback turtle has several "turtles of the best"</h1>
1. The largest body
The length of the dorsal carapace of adult leatherback turtle is 1-1.75 meters, the total length of the body is 1.83-2.13 meters, and the average weight is 300-500 kg. Adult leatherback turtles in the Caribbean have an average dorsal carapace arc of 1.55 m and an average weight of about 384 kg. Leatherback turtles are not only the largest surviving turtles and turtles, but also the reptile with the largest average adult (sexually mature) weight, with the bay crocodile weighing an average of about 230 kg in adults.
A male leatherback turtle was captured in Monterey, California, on 19 August 1981, with a body length of 2.54 meters and a weight of 865.45 kg.
In 1988, a leatherback turtle was captured at the mouth of the Jiaolai River in Shandong, Bohai Bay, with a body length of 1.83 meters, a back armor length of 1.4 meters, and an estimated weight of 500 kg.
In 2007, NOAA (United States Oceanic and Atmospheric Administration) captured a 607-kilogram leatherback turtle (above) in Monterey, San Francisco.
The largest individual recorded in history was found on a beach on the west coast of Wales. The dorsal armor is more than 2.2 meters long and weighs 916 kg. With this data, leatherback turtles can make it into the top five of reptile extreme weight.
2. The widest distribution range
Leatherback turtles are the largest turtles in the world, and are found in almost all tropical and temperate regions of the world. Based on different population genes, feeding sites, spawning sites and migration routes, leatherback turtles are divided into 7 subspecies. In the Atlantic Ocean, there are three subspecies of northeast, southeast and southwest; in the Pacific Ocean, there are two subspecies of east and west; in the Indian Ocean, there are two subspecies of northeast and southwest.
The distribution and subspecies division/figure of the leatherback turtle originate from NOAA
However, in some sources, only leatherback turtles are divided into two subspecies, the Pacific ocean and the Atlantic Ocean.
3. The longest migration distance
Because the leatherback turtle's favorite jellyfish is not a high-calorie food, so it can only eat a lot, the leatherback turtle can eat the equivalent of 73% of its own body weight in one day, fortunately, the jellyfish move slowly, the difficulty of catching is not large, but in order to eat enough jellyfish need to migrate long distances. Spawning grounds and areas of abundance are often far apart.
The Western Pacific Leatherback Turtle Migration Route/Map is from NOAA
Leatherback turtles that spawn in the Malay Archipelago in the western Pacific Ocean travel 16,000 kilometres to feed in the jellyfish-rich waters off the west coast of the United States, usually taking 10-12 months. The leatherback turtle, which lays its eggs on the coast of Gabon, feeds in the waters off Brazil and Uruguay and needs to cross thousands of kilometers and last more than 150 days. In addition to having superior swimming ability and endurance, it also requires the use of ocean currents to complete the journey across the Pacific and Atlantic Oceans.
4. Swim fastest
Leatherback turtles have oar-like forelimbs and a teardrop-shaped body, and their forelimbs can be up to 2.7 meters long, and the ratio of forelimbs to body is the largest among existing sea turtles. Leatherback turtles lose the β-keratin in their epidermis, have a leathery coat, and gain less resistance. Leatherback turtles can reach a speed of 35.2 km/h, faster than most fish, and this swimming speed is also the fastest among turtles.
5. The strongest diving ability
Turtles rely mainly on lung breathing, but can also use the cloaca and oral mucosa to assist breathing. Aquatic turtles generally live in shallow waters to facilitate ventilation, but leatherback turtles have strong diving ability.
Leatherback turtles have flexible dorsal carapace and squeezing-resistant trachea, and can regulate their metabolic rate so that their body temperature is higher than 18 ° C above their surroundings. Through these mechanisms, leatherback turtles can dive to depths up to 1280 meters below sea level, prey on jellyfish and cephalopods there, and hold their breath for at least 70 minutes. There is no doubt that the diving ability of leatherback turtles is the strongest among turtles and reptiles.
Seeing this, many people may wonder: Aren't leatherback turtles reptiles? Why can I regulate my body temperature?
Leatherback turtles do belong to reptiles, but they are extremely special "warm-blooded sea turtles".
<h1 class="pgc-h-arrow-right" > why aren't leatherback turtles "cold-blooded"? </h1>
Previous studies have divided vertebrates into internal and external temperature according to thermoregulation strategy.
Internal thermogeneity corresponds to thermostatic animals, also known as warm-blooded animals, mammals and birds, that is, internal heat sources can be used to maintain body temperature and put it in a stable range.
Extra-temperate strain temperature animals, also known as cold-blooded animals, have reptiles, amphibians and fish. That is, relying on external heat sources, such as sunlight and water temperature, to maintain and regulate their own body temperature. For example, reptiles such as crocodiles, snakes, and lizards like to bask in the sun; amphibians such as frogs and salamanders are mostly distributed in the tropics and subtropics; and fish are very sensitive to changes in water temperature.
But with the deepening of biological research, another thermoregulation strategy was discovered, between internal and external temperature, called mermothermic, and the leatherback turtle is this special mesothermic animal.
Comparison of leatherback turtles with prehistoric giant tortoises
Leatherback turtles are reptiles, but they can self-regulate their body temperature, which is very different from other reptiles. Adult leatherback turtles can maintain a body temperature of 25-26 °C in sea waters of only 8 °C, while in warm tropical seas, leatherback turtles have a body temperature of only 1-3 °C higher than the water temperature. To do this, leatherback turtles need to regulate the heat they generate and prevent it from dissipating into the surrounding seawater. It can use three methods to conserve heat in the body.
The first is the simplest way, which is the huge body size. The larger the animal's size, the smaller the relative body surface area (the ratio of body surface area to volume), and the slower the rate at which heat in the body is lost from the body surface. The huge size allows the heat in the body to be retained in the body relatively stably, which is called gigantotherrny .
As the largest turtle, the leatherback turtle can retain the heat in the body for a long time, making it difficult to lose. This mechanism, coupled with a second method, can also be used to explain why fat people are more afraid of heat than thin people.
The second method is the insulation layer. Mammals living at high latitudes have thick fur and fat, which is the insulation layer. The leatherback turtle also has its own insulation layer, which has a fibrous layer under its skin, and under the fiber layer has a rich brown adipose tissue, which is a specialized thermogenic tissue, rich in mitochondria, capable of efficient non-trembling thermogenic activities, which is equivalent to both the insulation layer and the electric blanket. However, this structure has the disadvantage of not being able to maintain the temperature of the head and limbs, and the blood flowing from the limbs back to the body will reduce the core temperature of the body, so the leatherback turtle needs a third method.
That is the convection switching system. The heat in the body of the leatherback turtle mainly comes from muscle movement, the pectoral muscles of the leatherback turtle are strong and independent, and the metabolism of the pectoral muscles in the sea water of 5-38 ° C can be very stable for heat output. There is a thick blood vessel layer in the trachea of the leatherback turtle, and the way of convection exchange makes the air entering the lungs equal to the body, so the leatherback turtle can breathe warm air even in cold waters.
The arterial bundles and vein bundles at the roots of the limbs of the leatherback turtle can transfer heat to each other, bringing cooling blood from the limbs and exchanging it with warm blood brought by other parts of the body, preventing the cooling blood of the limbs from lowering the core body temperature. In warm waters, leatherback turtles can also use this method to transport warm blood to their limbs to dissipate heat.
In these three ways, leatherback turtles can enter high-latitude and deep-water areas that are not accessible to other sea turtles. However, the above method is only effective for adult leatherback turtles, because the juvenile leatherback turtles are too small to retain enough heat, and the insulation layer and convective exchange system are not enough to maintain body temperature, so the leatherback turtle can only grow rapidly. Leatherback turtles are no different in size than other sea turtles when they hatch, with an average dorsal carapace of about 51.3 mm long and weighing about 46 grams, but growing much faster than other sea turtles.
The known growth rate of green sea turtles is about 2.2, but leatherback turtles are as high as 13, while crocodiles are only 1.9, which is why leatherback turtles can become the largest living adult average weight reptile because it grows so fast.
Moon fish
Leatherback turtles are not the only medium-temperature animals, porbeagle sharks, tuna, moonfish, echidnas, etc. all have the ability to self-regulate body temperature. And according to John Grady's research, dinosaurs may also be mesotophane.
John Grady's 2014 paper in the journal Science, "Evidence for mesothermy in dinosaurs," said dinosaur growth rates ranged from 4.8 to 16, ahead of most reptiles and fish, but not as fast as the vast majority of mammals. The growth rate of dinosaurs is roughly between thermostatic animals and thermostatic animals, which belong to the middle temperature animals. But a year after the paper was published, M. D. D'Emic objected that the john Grady paper miscalculated dinosaur growth rates. Therefore, whether dinosaurs are constant temperature, variable temperature or mesothermal animals still needs more research.
<h1 class= "pgc-h-arrow-right" > the survival status of leatherback turtles</h1>
Globally, the number of leatherback turtles has fallen by 40% over the past 30 years, while the number of leatherback turtles in the western Pacific has declined by 80% in the past century. The leatherback turtle is classified as a vulnerable species by the IUCN and is a Class I protected animal under the Convention on International Trade in Endangered Species of Wild Fauna and Flora, which was listed as an endangered species by the United States in 1970 and a national second-level protected animal in China.
Promotional poster: "Leatherback turtles can't recognize jellyfish and plastic bags"
At present, plastic litter floating in the ocean, discarded fishing gear, human bycatch and destruction of spawning grounds are the main threats to leatherback turtles, and international efforts are being made to increase the population of leatherback turtles. According to the number of spawning adult turtles and spawning in recent years, the downward trend in the number of leatherback turtles is being controlled, and it is predicted that the population will begin to increase around 2030, but only if the international protection of leatherback turtles cannot be relaxed.
The leatherback turtle is a very magical reptile, with a perfect medium temperature system, creating several biological miracles, and it has countless secrets waiting to be revealed.