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In July 2019, fishermen in the Mediterranean Sea south of Sardinia, Italy, accidentally pulled an unexpected mutant from the depths. Trapped in its net among hundreds of other fish, sharks and various marine species was a dark-mouth cat shark (Galeus melastomus), apparently born without skin or teeth, reports BGNES.
Although scientists have reported numerous cases of albinism, discoloration and other genetic mutations of the skin in sharks, this rare catch is the first and only known case of a shark living with a “severe lack of all skin-related structures , including teeth “.
Even stranger seems to be that the abnormal shark appeared to have led a relatively normal life, until its capture, says lead author Antonello Mulas. When he and his colleagues examined the shark, they found that it was about 3 years old, grew up in a typical environment, and had a stomach full of food when it died.
“Our first reaction was, ‘A shark without skin cannot survive,'” Mulas, a biologist at the University of Cagliari in Sardinia, told Live Science. “But, as Shakespeare said, there are more things in heaven and earth than you can imagine.
G. melastomus are common small cat sharks that can reach a maximum length of just over a meter, about the size of a baseball bat for a child. They are predominant in the northeast Atlantic and the Mediterranean, where they usually swim to a depth of 200 to 500 meters. True to its name, the inside of the jaw area is dark, as is the tissue-like sheath that covers its internal organs.
This inner darkness is clearly seen in the images of the “naked shark” from Sardinia, as Mulas and his colleagues call it in their paper.
The ‘naked’ shark was born without skin or teeth in the first world https://t.co/OMMoTOtV3h The three year old female without skin died with an empty mouth and a full stomach.
– 8323SABUROH (@ 8323Saburoh) October 2, 2020
The shark’s dark “insides” peek through its gills and transparent head, which contrasts sharply with the rest of its slim yellow body. The shark looks so abnormal that the researchers’ first impulse was to make sure it was not “alien,” jokes Mulas.
“There are more than 300 species of sharks and we wanted to make sure this is not a species we have never heard of,” Mulas added.
Researchers have discovered that the shark is not an alien after all, it is just an alien from other waters. The team’s investigation revealed that the cat shark is a 12-inch-long young female who is of normal growth for her age. In addition to seemingly losing the epidermis (the outermost layer of the skin), the shark also lacks teeth in the skin – small tooth-like structures that cover the skin of all sharks, a microscopic analysis revealed. These hard, spiky formations not only provide physical protection for sharks, but also make them faster and more agile swimmers, Mulas said.
In the absence of fur teeth, the naked cat shark was probably a weaker swimmer than its peers, but this obviously did not prevent it from successfully filling its stomach, nor did it lack teeth. In the shark’s intestines, the researchers found 14 foods, a cocktail of small cephalopods, crustaceans and bony fish. Because dark-mouthed animals generally swallow their prey whole, the naked shark’s bare mouth does not make it a less effective predator, Mulas said.
The shark’s abnormal appearance is almost certainly the result of a genetic mutation, the researchers conclude. This mutation can be completely natural or have been affected by exposure to chemical contaminants in the water. To get a better idea, the researchers will return to the spot where the naked cat shark was captured and sample the sediment from the seabed. This analysis should reveal if there was anything potentially harmful about the shark’s environment and if it could point the way to other similar strange sea creatures, Mulas said.
“Maybe we’ll find a two-headed shark or a Blinky fish (trio) from The Simpsons,” he concluded hopefully.
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