Austria 2023 3 Euro Colored Collector Coin – Swell Shark

The swell shark gets its name from its ability to inflate to about twice its normal size by swallowing water as a defense against predators. When the shark senses a threat, it bends its body into a U-shape, grips its tail fin with its mouth, and sucks in water. This increases the shark’s diameter, making it much harder for predators to bite or dislodge it. The swell shark can swell using water or air, which is held in the stomach until released. When releasing air, the swell shark makes a sound reminiscent of a dog’s bark. However, this is not the only remarkable feature of this shark – the swell shark can also glow green across its entire body. The biofluorescence of the swell shark was first reported in 2014. To achieve this, the swell shark converts incoming ultraviolet or blue light into green light. A special pigment in the shark’s eyes allows them to see the neon green color. Human eyes lack this pigment, so we need ultraviolet lighting to see the green glow of the swell shark. The light areas of their skin glow more intensely than the dark ones. Why the shark does this is not yet fully understood, but it is believed that this process helps sharks recognize each other and distinguish between male and female of the species. It may also serve as camouflage, as the molecules protect against bacteria and algae and simply glow. Swell sharks are non-aggressive and considered harmless to humans.