For a long time, in our impression, sharks are ferocious hunters in the ocean, and people think that sharks are pure carnivores. But there is one type of shark that not only eats meat, but is also particularly vegetarian. They are Sanshui’s popular science guests in this issue—na

For a long time, in our impression, sharks are ferocious hunters in the ocean, and people think that sharks are pure carnivores.

But there is a kind of shark that not only eats meat, but is also particularly vegetarian. They are Sanshui's popular science guests in this issue - narrow-headed hammerhead shark .

For a long time, in our impression, sharks are ferocious hunters in the ocean, and people think that sharks are pure carnivores.

1. Family symbol, an alternative "bun" on the head

Before introducing the narrow-headed hammerhead shark, let's first get to know the famous hammerhead shark family.

Hammerhead shark, also known as hammerhead shark , is the collective name for fish in the class Carcharhinidae and the family Hammerhead Shark, named after the shape of its head. From a distance, it looks like two buns. If it is straightened up, it probably looks like the flag head on the head of a woman in a Qing palace drama.

The bun of a concubine in the Qing Dynasty

Hammerhead shark: The shape of my head is not combed

Although there are more than one species with hammerhead-like heads, hammerhead sharks should be the cutest among such creatures. Yes.

Since humans first discovered hammerhead sharks more than 200 years ago, the question of "why they have such strange-shaped heads" has been puzzling the scientific community, and scientists still cannot explain it.

2. The most petite member of the family

The narrow-headed hammerhead shark has an average body length of 90-120 cm, the longest is about 150 cm, and the heaviest is about 10.8 kg. It is a small shark and is the smallest among the hammerhead shark family. member, the head is also the narrowest among hammerhead sharks.

Their heads are spade or hat-shaped, lacking a notch in the midline. The side of the head protrudes into a short circle, and the front edge is rounded. The eyes are located at the ends of evenly rounded lobes of the flat head, thus increasing the field of vision.

Narrow-headed hammerhead sharks are distributed in the warm waters of the Atlantic and Pacific Oceans. They like to inhabit continental shelves and small island shelves, and live in reefs, estuaries and shallow bays with a water depth of 12 meters. In winter they migrate south or into deeper coastal waters.

Narrow-headed hammerhead sharks usually form groups of 5-10 individuals, and sometimes they form large groups of hundreds or thousands. They mainly prey on crabs, shrimps, small fish, etc.

3. Not only does it like to eat meat, it also likes to chew seaweed

. It has sharp teeth and has super hunting ability. It has few natural enemies and has almost occupied the top of the marine food chain. However, it has been Researchers found that in addition to eating small fish and shrimps, they also like to eat seaweed.

In 2007, scientists analyzed the stomach contents of bonnethead sharks captured from Mexico and found that half of the food of some individual bonnethead sharks was plants, and they were suspected to be omnivores.

The narrow-headed hammerhead shark bit off the seaweed tied to a long pole

In order to find out the truth, scientists caught and raised five narrow-headed hammerhead sharks and fed them "squid and seaweed rolls"-wrapped with fresh squid slices. Pick up a handful of seaweed. It looks like meat on the surface, but is actually 90% grass - sharks love to eat it, one bite at a time. After feeding

for three weeks, when weighed on the scale, all five sharks were fat. It can be seen from the feces that they digested more than half of the seaweed, and enzymes for digesting plants were also extracted from the intestines. Even in the blood of sharks, large amounts of substances derived from seaweed have been found.

This confirms that the bonnethead shark is omnivorous, and seaweed can account for about 60% of its daily diet. They are also the world's first confirmed omnivorous sharks.

4. Why do bonnethead sharks like to eat vegetarian food?

Scientists speculate that the reason why bonnethead sharks like to eat seagrass may be because they eat it by mistake and then become a habit. Hammerhead sharks often feed on "seagrass lawns" covered with seaweed, where they may accidentally eat the seaweed while catching crabs and fish. Over time, it gradually developed the ability to digest seaweed. A laboratory video released by

shows that young bonnethead sharks eat the most seagrass. For example, a young bonnethead shark ate a "salad dinner" containing 90% seaweed and 10% squid.

Some scientists speculate that ocean conditions forced the bonnethead shark to undergo a food transition.All kinds of organisms in the earth's ecosystem are interconnected. As the earth's environment continues to deteriorate, the living conditions of marine organisms are also gradually declining. One of the most obvious manifestations is food shortage.

After all, when living conditions deteriorate, the survival rate of omnivorous marine organisms is much higher than that of monovorous marine organisms.

At present, the reason why the bonnethead shark likes to eat vegetarian food has not yet been fully concluded. Scientists estimate that the total number of bonnethead sharks is 4.9 million. The impact of their collective vegetarian diet on the seagrass ecosystem requires further evaluation.

5. Unique digestive system

So the digestive systems of herbivores and omnivores are completely different. How does the bonnethead shark manage to eat both meat and grass?

Researchers first discovered strong acids in the stomach of two-headed sharks. These strong acids can dissolve seaweed, making it possible to digest seaweed.

But strong acid alone is not enough, because dissolution does not mean absorption. The two-headed shark can both dissolve seaweed and absorb nutrients in seaweed. There are obviously other unknown ingredients helping it, so scientists Continue to study.

Later, the digestive enzyme , which can digest the hardest parts of seaweed, was discovered in the bonnethead shark. With this digestive enzyme, the bonnethead shark's stomach can dissolve the plant cellulose of seaweed.

Plant fiber is like a protective film that protects the internal nutrients of plants. If you want to use plant energy for your own use, you must first dissolve the fiber wall. Because it can dissolve seagrass fibers, bonnethead sharks are able to absorb the energy of seagrass.

6. The little shark without a father

How can the little shark not have a father? It turns out that some studies found that when bonnethead sharks were kept in captivity for long periods of time in aquariums, the females would impregnate themselves without any contact with other male sharks.

This method of reproduction is called parthenogenesis. Other vertebrates that can undergo parthenogenesis include Komodo dragons and blacktip sharks.

Parthenogenesis is also called parthenogenesis, that is, eggs can develop into normal new individuals without fertilization. Parthenogenesis is a reproductive phenomenon common in some primitive animal species.

simply means that organisms do not need male individuals, and individual females can also reproduce by copying their own DNA.

- Source of the article -

Internet data compilation

If there is anything wrong, please inform us to delete it

editor | Sanshui·Crispy Shark

reviewer | Chen Qiao

chief planner | Uncle Hao

END