If you've never heard of skinless sharks before, there's a good reason for that. For the first time, scientists have found a trawler in the waters of Sardinia. The team found a cat shark that appeared to have no skin. The discovery was published in the journal Fish Biology and shares many surprising revelations.
Peeling cat sharks
After studying the shark's anatomy, the researchers found that the fish did not have any structures normally associated with elastic branching skin, which contained the shark. It is believed to be the only shark that can swim freely in the depths of the ocean.
Often, for mechanical and chemical defense purposes, the skin plays a vital role for elastic sharks. The skin secretes a type of mucus called the first line of the fish's immune system. This helps prevent microbes from forming colonies on the animal's surface because it contains antibacterial proteins that help protect sharks. It consists of fine teeth, which are overlapping, tooth-like structures, and also provide a strong mechanical defense barrier against exopsites and other types of predators.
Sharks without skin layers
The shark that was found was the Galutes melastomus black-mouthed sawtail shark, which unfortunately did not have this "skin" protective layer. Incredibly, it also lacks any type of skin-related structure, including the epidermis, dermal dentures, parts of the dermis, and teeth.
The shark was found in July 2019 at a depth of 1640 feet in Sardinia. Skin is often crucial to the survival of fish, and although finding a lack of skin can be fatal, sharks are in good health and well-developed.
When it comes to feeding, this shark is lucky because it devours the entire prey and therefore has no teeth to eat. However, due to the lack of external dermal dentin "teeth", there are no typical marks of black mouth black.
This shark does not have the typical markings of its kind
When trying to understand how the shark ended up completely losing teeth and peeling, the researchers thought the reasons might be related to humans. The authors of the article say that it is likely that long-term exposure to chemically polluted water, as well as warming (acidification) of the oceans caused by climate change, are all possible causes. It may also be unrelated to humans and is caused by natural errors in the development of animal embryos.
Still, before determining the exact cause, the researchers stress the importance of understanding the fact that our actions will cause many anomalies to marine animals (as well as non-marine animals), directly or indirectly.