What is the use of the hammer head of the hammerhead shark?

Recently, the world-renowned magazine Science published an article stating that the "ocean hunter" hammerhead shark is the first fish discovered to "hold its breath" . Its unique deep-sea ability not only improves its survival adaptability, but also helps it catch prey. This article quickly attracted the attention of the industry.

In fact, compared to "holding your breath", people are more interested in the strange head of the hammerhead shark.

The "hammer head" of the scalloped hammerhead shark (Image source: biogeodb.stri.si.edu)

In movies and TV dramas, the heads of ferocious and brutal sharks, even the three-headed shark and the nine-headed shark (both of which are in science fiction movies and do not exist in reality), are all pointed.

The hammerhead shark has two things on its head that look like a bun, protruding to the left and right sides in a "T" shape, and the whole shape looks like a hammer. Therefore, it is also called the hammer shark or hammerhead shark (English name: The Hammerhead Shark, "Hammerhead" means "hammer head").

What's even more strange is that its eyes are located at both ends of the hammer head (i.e. the top of the double buns), and it looks a bit like Yang Ren in TV dramas such as "Investiture of the Gods", who has two small hands growing out of his eye sockets and eyes growing in the palms of his hands.

What is the purpose of the hammerhead shark's distinctive hammer head?

The hair buns of concubines in the Qing Dynasty (Source: Sun Yat-sen University Marine Science Network)

Weird eyes have many benefits

The fittest survive. The physical features of animals are often related to hunting, movement, and escape. For example, wolves have long and thin legs that are good for running, and monkeys and apes have soft and powerful forelimbs that are good for climbing.

The hammerhead of the hammerhead shark is used to prey on marine animals. Its head can be half the size of its body and is about 1-3 meters wide. From the front, you can only see its double-hammer head because the body is blocked behind it. With such a large head, it is no problem to hold down ordinary fish.

According to research by marine biologists:

When hammerhead sharks catch stingrays, which are disc-shaped, agile and good at hiding in the ocean, they usually attack suddenly, hold them down with their hammer heads, and bite their fins until they enter their stomachs.

Hammerhead shark (Source: watermark)

The hammer head acts like a metal detector, helping the hammerhead shark sense electromagnetic fields and hunt prey hidden in sand and rocks.

To be precise, the hammer head is a large radar with a large number of Laurentia ampulla structures, which helps them detect a wider range of sea areas and find prey more efficiently.

To avoid being hunted, some small fish or shrimps and crabs often hide in the gravel or rubble at the bottom of the water, with only their eyes exposed. Laurent's ampulla is a relatively special skin sensory organ of cartilaginous fish, a deformed structure of the lateral line canal, distributed on the dorsal and ventral sides of the head. Hammerhead sharks sense the weak electric field in the body of their prey through Laurent's ampulla, and quickly discover and prey on it.

Original article by Keller, a marine biologist, in Science magazine:

"There have been other papers before that have shown sharks can detect and respond to magnetic fields, but ours is the first to show that they (hammerhead sharks) have a map-like perception ability."

Another use of the hammer head is to speed up the swimming speed of hammerhead sharks. This is reflected in three aspects:

▶ First, it is easy to turn, and its turning speed is twice that of ordinary sharp-nosed sharks;

▶ Second, it helps to maintain body balance when turning;

▶ The third is to use the "head-down" posture that ordinary pointed-nosed sharks do not have to provide more power for swimming.

The most useful organ on the hammerhead for catching prey is the eyes of the hammerhead shark. They are located at both ends of the head and have an average width of about 1.5 to 3 meters.

Such a distance can enhance its perception of ocean depth and detect prey or natural enemies farther away.

According to experimental studies:

Hammerhead sharks use their eyes to accurately judge distance, especially the distance between them and the prey they want to kill. In addition, their eyes have a 360-degree field of view, which means that they have almost no blind spots in all directions. They can truly "see in all directions" (i.e., the six directions in the water, up, down, front, back, left, and right).

Yang Ren with strange eyes in the TV series "The Investiture of the Gods" (Source: First Film and Television Network)

A new form of ferocious predation

Everything has a cause.

From the perspective of biological taxonomy, the hammerhead shark belongs to the family Sphyrnae, under the order Carcharhinidae, class Chondrichthyes. Common species include the smooth hammerhead shark, bonnethead shark, scalloped hammerhead shark, T-neck shark, etc. The largest species is the smooth hammerhead shark.

Hammerhead sharks are mainly distributed in temperate and tropical oceans. They usually travel in groups during the day and become "lone wolves" at night.

The body length of the hammerhead shark is about 1-6 meters, and the adult is 3-4 meters, which is equivalent to the height of two adults. Its life span is about 20-30 years, which is relatively long among fish.

A pair of hammerhead sharks (source see watermark)

Hammerhead sharks are ferocious carnivorous marine animals (except for the bonnethead shark, which eats both meat and vegetables and likes to eat seaweed).

In addition to preying on mollusks, crustaceans, turtles, and seabirds, they also attack humans.

Studies have shown that:

The hammerhead shark attacks mainly when it is threatened or senses human ill will, and it uses its hammer head to demonstrate when attacking. It does not actively attack humans or ships, which is the biggest difference between it and the common scalloped shark.

Media reports say that most hammerhead sharks are "shy" and people generally fail to spot them when diving. Because their hammerheads are particularly sensitive, they usually spot divers from a long distance and quickly swim away to avoid "contacting" humans.

The hammerhead shark, which does not actively attack humans, is the youngest of its kind. Although sharks have a history of 300-400 million years, hammerhead sharks have only evolved from marine animals to the present 20 million years ago.

The hammer head of the hammerhead shark is called the cephalic lobe or cephalic wing by scientists. It is light and thin, like a pair of wings.

Head wings are originally the patent of flying animals such as hoopoes and pterosaurs. It is also a rare thing to see them used in marine animals. It is precisely this pair of thin head wings that make the hammerhead shark the focus of many netizens.

References:

1. "Sharks also eat grass: the first omnivorous shark confirmed", Xinhuanet

2. Optimization of extraction and gel formation conditions of salt-soluble protein from hammerhead shark muscle by response surface methodology, Xu Dalun, Yan Weihua, Yang Wenge, etc., 2011

3. Why Do Hammerhead Sharks Have Heads Like Hammers? by Emily Merkford, 2016

Author: Wei Deyong, member of Shenzhen Writers Association, Guangdong