(ORDO NEWS) — For a long time it was believed that whale sharks feed mainly on small animals. But scientists now know that their diet includes quite a lot of algae. In other words, this fish is the largest omnivore on our planet.
The whale shark ( Rhincodon typus ) is the largest of the sharks and the largest fish on the planet: its length reaches 20 meters and its weight is 34 tons, which is comparable to the size of an average sperm whale.
True, unlike this deep-sea squid hunter, the whale shark is a slow and rather peaceful animal that obtains its food by filtering sea water.
Although on land the largest animals are herbivores, in the sea, blue whales and whale sharks feed mainly on small animals, from tiny crustaceans to small fish.
For a long time, it was believed that plant foods were too nutritious for such huge animals to consume them.
But now, with biopsy results from whale sharks, scientists have found that these fish actually digest just about anything they put in their mouths.
To find out exactly what whale sharks ate, the researchers collected samples of possible food sources ranging from tiny krill to large algae.
They then compared the amino acid and fatty acid composition of the potential food with that of the whale sharks themselves, as well as their feces.
It turned out that a significant proportion of the diet of the studied animals is not plankton and small animals, but sargassum brown algae , which often breaks away from the bottom and floats freely with the flow, forming thalli.
In contrast to the results of the analysis of shark feces, these data prove that algae are not just swallowed by sharks: they are digested and used to build the body, that is, they are included in the normal diet of the animal.
Curiously, traces of krill were found in the feces of whale sharks, but it was semi-digested. That is, although sharks eat small crustaceans, they almost do not use the resulting nutrients in building their organisms.
The new data not only expands our knowledge of the diet of giant fish, but also allows us to reassess their vulnerability to ongoing ocean pollution and adjust the diet of whale sharks kept in the world‘s aquariums.
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