When we think of wild animals we are able to name species that are completely different from each other, be it by their coat pattern, their habitat, their food, their locomotion among others. Beyond what we can see, the genetics and metabolism of species vary greatly and this gives us some surprises: did you know that it is estimated that the oldest animal in the world is 518 years old?
That means that his birth was around 1505. It also means that he was in his habitat when Brazil was "discovered", during the outbreak of bubonic plague in London, and that he remains there after the smallpox pandemic, 2 world wars, the covid pandemic and several other historical events. But what animal is this that was born in the 16th century?
Somniosus microcephalus, which means "small-headed sleepy", is a chordata, of the chondrichthyes class and squaliform order: the greenland shark. The 518-year-old individual was last recorded in 2023 by USP researchers in the Caribbean Sea. The species itself is poorly studied due to the difficulty in finding it and this last appearance raised the hypothesis that its area of occurrence is larger than we imagined, or that we can already see impacts of anthropic threats on its behavior.
At first, despite its name, the shark is not only present in Greenland, in the Arctic Ocean, but also in the North Atlantic and in the Russian High Arctic, that is, they live in cold waters wich can reach - 2 degrees Celsius. It can be seen on the surface up to 2700 meters deep. Its size varies between 2m and 4.5m, but it is possible to reach 7m, being the female larger than the male.
Their scientific name comes from the fact that they are slow animals, swimming at less than 2 km/h. Their metabolism is also slow, so that these animals grow about 1 cm per year. More recent studies indicate that females reach sexual maturity at 134 years and that the capacity of the uterus is 200 to 324 pups per pregnancy. The gestation time is still unknown.
Unlike other sharks, the age of this species is not estimated by the growth rings of their vertebrae, because they do not have these rings. The age of these sharks is calculated by layers of the lens in the eye, which grow throughout their life, and by radio carbonization of the tissue inside.
But the surprises don’t stop here!
These sharks eat a variety of fish, invertebrates and other prey. Remains of polar bears, reindeers, horses and other large land mammals have been found in their digestive systems. To survive in low temperatures they have high levels of chemical substances that act as antifreeze and prevent the formation of ice crystals in your body. Besides, their flesh is poisonous. Ingestion may cause diarrhea, vomiting, disorientation and seizures, with symptoms similar to severe drunkenness.
Last but not least, the species is classified as "vulnerable" by the International Union for Conservation of Nature (IUCN). This species is not actively
hunted more, but still caught accidentally in fisheries. Studies are still needed to better understand their characteristics, behaviors and threats.
Author: Anna Karolina Vasconcelos Marin Zimerer
References
National Geographic. Greenland shark. Available https://www.nationalgeographicbrasil.com/animais/tubarao-da-groenlandia.
in:
NIELSEN, Julius et al. Assessing the reproductive biology of the Greenland shark (Somniosus microcephalus). PLoS One, v. 15, n. 10, p. e0238986, 2020.
Ocean. Greenland Shark (Somniosus microcephalus). Available in:
International Union for the Conservation of Nature (IUCN).Greenland Shark (Somniosus microcephalus). 2019. Disponível em: https://www.iucnredlist.org/species/60213/124452872
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