Shark

Sharks are the most dreaded sea animal falling under the category of fish community. In movies, these animals are largely presented as villains and dangerous. Originated 420 million years ago, there are various categories of this sea fish. Selachimorpha, Acanthodians. Cladoscelacahe, and other subclasses of sharks are found in different parts of the world.

What is a Shark?

Sharks are the superorder of fish. Like other chondrichthyes, these sea fish have skeletons made completely out of cartilage, which are tough and rubber material. Shark scientific name is Selachimorpha and falls under the subclass of Elasmobrachii. There are more than 500 species of sharks and range in different sizes. The maximum depth they can go into is 2000 meters and found in both sea and fresh water.

Some of the common types of shark fish are- hammerhead shark, great white shark, tiger shark, and Mako shark. Most of these sharks are known for their cold-blood, but white sharks and mako sharks are warm-blooded.

Types of Shark Fish

There are different types of shark fish found globally. All these centuries, sharks have been resilient and survived five global mass extinctions. One such is the Permian- Triassic extinction that almost wiped out 95% of life on the earth. This also has given birth to some of the sub-species of shark fish, the count of which goes to more than 450. Some of these are:

• Whale Shark

The scientific name for this shark is Rhincodon Typus, and are cartilaginous fish. This is the longest sharks’ fish in the world. This slow moving shark can grow up to 12 meter and weigh 20 tons. At first look, this type of fish seems scary, but are not predators. The diet of this fish consists of fish eggs, crab larvae, krill and other such. Whale sharks have the ability to survive without food for weeks, and during this situation, they feed on seaweed and other plants. Unfortunately, their population is decreasing.

• Angelshark (Squatina)

This shark fish are the most abundant species, swimming on the coastal waters of Northern Africa. Angelsharks are normally found in different parts of the world, but are mostly seen in western and eastern part of the Atlantic and Pacific oceans. Most of the time, these shark species stay buried under the sea sand with only eyes poking out for attack. Over the years, there has been too much fishing for this shark, resulting in extinction.

• Shortfin Mako Shark

With the scientific name Isurus Oxyrinchus, it is the fastest one of all the sharks with a speed of 32 km. These sharks carry pointed snouts and long gill slits. They are the most aggressive predators having marine fish as their food. Some of these are marine mammals, tuna and swordfish. In many cases, these sharks have also attacked humans.

• Hammerhead Sharks

This group of sharks belong to the family of Sphyrnide, and are the most recognized ones. The hammer shaped head makes them look different from others. These sharks are fierce predators and live in warm tropical waters. They use their wide heads to trap stingrays by pinning them to the seafloor. They have a peculiar eye placement on the wide head allowing them to scan different areas. These sharks do not lay eggs, but give birth to live 50 pups at one go.

• Zebra Shark

Falling in the family of Stegostomatidae, zebra sharks are large and reside in the shallow coral reef in the tropical waters of the Western Pacific and Indian Oceans. They got this name due to yellow stripes on the body similar to the zebra. These sharks hunt small fish, snails and crabs. They are harmless to humans, and there have been no cases of human attacks.

• Basking Shark

Basking Shark is the longest shark of all and they got long gill slits. These sharks can grow up to 12 meters and have a predatory look. However, they are harmless and most of the time their mouth remains open. Basking sharks are few of those species, which live in temperate latitudes. Moreover, they are social animals always living in-group.

• Bull Shark

One of the aggressive sharks, Bull Sharks hunt prey in tropical water and even attack humans. These sharks are short, blunt and carry quarrel tendencies. They are fast and eat almost everything coming on their way. Other sharks, dolphins and other fish are common preys.

• Tiger Shark

The most common shark animal, it is the fiercest creature falling under different types of sharks. These are quite slow-moving fish and carry an omnivorous diet. They carry an incredible smell and eyesight sense and are the best scavengers. Tiger Shark can grow more than 4 meters and weigh up to 1400 pounds. They got the most powerful jaws. They prey on squids, sea turtles, and shells. In many unfortunate cases, they even attacked humans.

• Blue Shark

This blue shark has wide-open eyes and small mouth, making them the cutest ones. One of the interesting shark characteristics it carries is the indigo color, which its body has, changes to dark grey. Squid and Herring are two of their most favorite foods, but in many cases, they even go for turtles and whales. Blue sharks are not aggressive to humans, but are friendly. They in fact approach divers, making them the most curious fish.

• Nurse Shark

Nurse Shark is the sedentary type of all sharks and are called the couch potatoes because they keep resting throughout the day. They are slow in nature. One of the fun facts about sharks like Nurse is they use pectoral fins to walk across the bottom of the sea. They carry a fleshy sense of organs, known as barbells. They drag it across the sand when looking out for the prey.

• Thresher Sharks

These sharks are large and fall under the family of Alopiidae. During the attack, these sharks sling the scythe-shaped tail over its head at the speed of 128 km/hour. This creates a huge impact on the prey killing it right away.

About Senses

One of the interesting facts about shark animals is they have a good smell essence and eyesight.

• Smell Sense 

Sharks have a good smelling sense and is located in the short duct between the anterior and posterior of the nasal opening. Some types of shark species have so powerful smell sense that they can detect as little as one part per million. Also called the olfactory bulb, the size varies across different species. In cases of low visibility, shark species have large olfactory bulbs. Furthermore, these sharks have a strong ability to determine the direction of the given scent completely based on the scent timing.

• Eye Sight

Like a strong smell sense, sharks also have strong eyesight. They have the tapetum lucidum tissue, which is placed behind the retina reflecting light back. The effect of this tissue differs according to the type.

• Hearing

Some types of sharks have a strong sense of hearing. They can possibly hear their prey from miles. There is a small opening on each side of their head, which directly leads to the inner ear through a thin channel. This makes their ear listen sharply.

Reproduction of Sharks

The lifespan of the shark is more than 20 to 30 yrs. Spiny dogfish, one of the types of shark has the lifespan of 100 yrs. Similarly, whale sharks can live for 100 yrs. When it comes to reproduction, unlike other fish, sharks produce a small number of young ones, which are well developed. They invest a lot of energy to reproduce and develop young ones. The reproduction in shark community takes place in three stages-

• Oviparity

Which also means laying eggs, Oviparity is an important stage. Chimaera, skate, and other species of sharks produce and lay eggs in a tough leathery egg case. Usually, female sharks take a long time to lay eggs, ensuring they get fixed in a safe place and take 6-9 months to hatch.

Completely depending on the species, some sharks attack their egg cases in a substrate. This can be either in seabed, coral reef or seaweed. The protective capsule inside which eggs stay acts as the life-support machine. The embryo inside the capsule absorbs all the nutrients before hatching. Once the eggs are hatched, the case is washed away in the seashore.

• Ovoviviparity 

In this, instead of laying eggs, the female will carry the newborn in her body. This is to provide extra safety to newborn from predators. In the process, the embryos develop within an egg having a thin membrane. Once it is developed, baby sharks are hatched. In many species, pups do not born immediately, but stay in the uterus.

• Viviparity(live birth)

This is the most advanced reproduction method in sharks. Under this process, the baby shark develops inside the female shark, and receives all the nutrients and oxygen required for the growth.

In many cases of shark species, female sharks reproduce babies without the requirement of male to fertilize. This process in science is called as Parthenogenesis (or ‘virgin births’). Zebra sharks, Blacktips and Bonne heads are some of the species.

Some Interesting and Fun Facts about Shark

• Sharks Do Not Carry Bones:

Like few other fishes, sharks do not have bones, but use gills to filter oxygen coming from the water. There are some special types of shark fishes called 'elasmobranchs" which translates into fish made through cartilaginous tissues. Rays, sawfish and skates are few of them whose skeletons are lighter in weight.

• They Have a Good Eyesight

One of the important shark characteristics is they have a good-eye sight. They can swim easily during the night and see colors. The reflective layers at the back of the eyeballs are called tapetume, making it easy for sharks to see during the night.

• They Carry Special Electroreceptor Organs

There are small black spots near the nose, eyes and mouth. These spots are called the Ampullae of Lorenzini. It helps in sensing electromagnetic fields and temperature shifts in the ocean. This is one of the unique shark features.

• Skin of the Shark is Quite Similar to the Sandpaper

The skin of the shark is almost identical to the sandpaper. It is made up of tiny teeth- like structures called placoid scales and dermal denticles.

• They Can Go in Trance Mode

Among all the unique shark features, this is one of the unique one. When sharks are flipped upside down, they go into the trance state. This is the reason why many animal scientists while examining sharks turn them upside down.

• Sharks Age Can be Said through Vertebrae

Vertebrae carries concentric pairs of opaque and translucent bands. If the vertebrae has 10 band pairs, then the shark is of 10 yrs. However, this assumption may not always be accurate. The age of the shark can also be determined through the size and deep species study.

• Not all Sharks Carry Same Teeth

Different sharks carry different teeth. For example, Mako sharks carry pointed teeth, while the white sharks have triangular ones. The sandbar shark has 35000 teeth throughout its lifetime.

• Sharks Carry Sixth Sense

Sharks are the most unique sea fish that carries some unique features. One such is they carry sixth sense. It helps them to hone the prey during the final phase of the attack.