In the warm seas of Indonesia, a huge shadow glides just below the surface of the water with its mouth wide open. Its length is more than 18 meters, but there is nothing to be afraid of: it is whale sharkthe biggest fish in the world. Longer than a school bus and heavier than twenty cars – more than 20 tons – this giant swims slowly and calmly and is one of the most peaceful animals in the ocean.
Big as a bus, but harmless
Its name is a little misleading: the whale shark is not a whale, but a real shark. They call it a “whale” only because it is huge and feeds like large cetaceans, that is, by filtering the water. Its giant mouth can open one and a half meters, but there are no sharp teeth inside ready to bite: this giant feeds planktonthat is, tiny organisms, fish eggs and small crustaceans floating in the water.
When a cloud of plankton or millions of fish eggs appears on the surface, the whale shark slowly glides just below the surface of the water with its mouth wide open and “sucks in” everything. Sometimes its back and fins even stick out of the water as it passes through food-rich areas. Scientists call this way of eating filtration: The animal retains food and releases only water.
A friend is always there
The whale shark often travels in company. Little goldfish Golden Trevally (Gnathanodon prominent), follows him swimming close to his head, especially when he is young. Why? Thus, near the giant he is safer from predators, he travels “freely”, using the current created by his large body, and collects scraps of food. The whale shark, in turn, neither gains nor loses anything: scientists call this type of coexistence commensalism.
Indonesian fishermen and gentle giants
In a special place Baya in Cenderavasi In Indonesia, whale sharks gather around Baganfloating wooden platforms used by fishermen. Small baitfish get stuck under these platforms, and giants have learned to catch there. To prevent them from tearing their nets, fishermen throw them some small fish: so these huge animals stand almost vertically to eat the leftovers, under the amazed eyes of those who watch them.
The cloak of stars is like a fingerprint
The scientific name of whale shark is Rincodon typewhich means more or less”giant covered in stars“. And the pattern is beautiful: its dark skin is dotted with white spots, uniquely positioned for each specimen, like our fingerprints.
Marine biologists have managed to take advantage of this feature in a clever way: they use a program designed to Hubble Space Telescopethe same one that was used to measure distances between stars and galaxies in order to “read” the spots on a shark’s skin. This way, they can recognize each animal and follow it for years, learning where it travels and how it lives. The giant of the oceans, studied with the help of space instruments: nature can sometimes truly surprise.
Fonte: Minden Photos