Shark: The External Anatomy, Head, Trunk, and Tail
Introduction
The class of Chondrichthyes, or cartilaginous fish, includes an ancient group of fishes known as sharks. In addition to skates and rays, sharks have relatives as well. Marine fish make up the majority of cartilaginous species. Although cartilaginous fish have been thought of as being primitive for a long time, more recent studies have suggested that these fish evolved from bony fish progenitors and are likely specialized fishes.
External Anatomy
The head, the trunk, and the tail are the three parts of the shark’s body. The head is measured from the snout’s tip to the gill slits’ caudal border. The ventral apertures for the anus and urogenital organs are located further along the trunk from there. From these holes, the tail extends caudally. The shark’s body is fusiform, or torpedo-shaped.
On the dorsal surface, the skin is greyish, and on the ventral surface, it is whitish. This is an illustration of counter-shading, a defensive adaptation that lowers the possibility that a prospective enemy may see the shark from above or below, and an offensive adaptation that may lower the possibility that a possible prey might see the shark in time to flee. Small, angular placoid scales, also known as dermal denticles, cover practically the entire surface of the skin and project posteriorly from the body wall. The placoid scale has a centre pulp chamber, an outer coating of dentine, and a small amount of enamel covering the dentine, similar to the basic structure of a tooth. Each scale’s base is enmeshed in the skin.
Sharks have fins that are both paired and unpaired. Two dorsal fins as well as the caudal fin are among the unpaired fins. Other than dogfishes, most sharks also have an anal fin. The cranial dorsal fin is larger than the caudal dorsal fin, as it is in almost all other shark species. In swimming, the dorsal fins serve as vertical stabilizers.
The presence of two long spines, one of which is situated directly anterior to the base of each dorsal fin, is a distinctive characteristic of the spiny dogfish. These spines have glands at their bases that can release poison when they puncture potential predators. Before dissection, it is advisable to remove the spines.
The caudal fin is the third unpaired fin. The dorsal lobe of this fin is noticeably larger than the ventral lobe, making it heterocercal. The animal can travel across the water with the help of its caudal fin. More force is produced by the larger dorsal lobe than the smaller ventral lobe. With each tail movement, a downward and forward thrust is produced. The shark’s paired fins stand in for another characteristic of vertebrates, paired appendages. Two pairs of paired fins make up the spiny dogfish. The surfaces and short bases of the front pectoral fins are semi-flexible. The dogfish moves forward in a straight line because of its tilt, which offsets the tail’s downward thrust. They function similarly to an airplane’s elevators and horizontal stabilizers in this regard. The pelvic fins, which are situated on either side of the cloacal entrance, make up the other pair of paired fins. These serve as stabilizers as well. Males and females have different pelvic fin shapes. They are altered in the male in preparation for sperm transfer during copulation. A rod-like, grooved clasper is formed on the medial surface of each pelvic fin in the male. The clasper is placed into the female’s cloacal orifice during copulation, and sperm is transmitted.
The two external nares are located on the rostrum, the pointed anterior end of the snout. Two openings—an incurrent aperture and an excurrent aperture—are visible when a naris is closely examined. The nares are sacs through which water flows, as this diagram demonstrates. The shark has a particularly sensitive collection of chemoreceptors because of the olfactory epithelium. The ventral mouth is one of the most noticeable aspects of the head. There are many teeth in the mouth. These teeth are altered placoid scales. Several rows of erupting teeth can grow to fill in any gaps behind them. The prominent eyes are on either side of the head. The eyes are shielded by fixed upper and lower eyelids. The transparent cornea covers each eye. The amount of light entering the eye is regulated by a coloured iris. A spiral is located directly dorsal and posterior to each eye. The spiracles are the initial gill slits. When the mouth is shut, water passes through them into the pharynx, allowing breathing to continue. The water flow through the spiral is controlled by a valve.
Five external gill slits are located above each spiral. Through the gill slits, the body expels the water ingested through the mouth or spiracles. All vertebrates eventually grow gill slits, which are a fundamental feature of vertebrates. Two endolymphatic pores, or the entrances of the endolymphatic ducts, are located behind the eyes on top of the head. The inner ears of the shark, which are connected to the endolymphatic ducts, are responsible for hearing and balance. Numerous pores on the ventral side of the rostrum lead into the Lorenzini ampullae, which are sense organs derived from the lateral line system. They play a role in the sense of minute variations in electrical fields and are crucial to the shark’s ability to feed and navigate. The body has a distinct lateral line running down each side. In reality, the lateral line is a highly developed sensory system that can pick up on vibrations and water currents. The lateral lines let the shark steer its body in a stream and avoid obstructions. The cloacal opening, which serves as the common external opening for the reproductive, excretory, and digestive systems, is located on the ventral surface between the pelvic fins.
Shark Facts
Sharks occur in over 400 different varieties. Each type of shark has a distinct appearance, diet, and behavior. Sharks may be found in all four oceans on the planet. Some sharks can fit inside a fish tank, while others are smaller than a school bus. Sharks come in a wide range of hues. Their skin tone usually makes it easier for individuals to blend in with their surroundings. However, certain sharks that dwell in the ocean’s deepest regions have sections that light at night. While some sharks can survive in freshwater, most sharks dwell in saltwater. Sharks all have different characteristics that make them special or make them unique. Sharks are a type of fish. Sharks and common fish have several similarities as well as differences. The cartilage that makes up a shark’s skeleton. Bones make up the skeleton of fish. The tough, flexible material found in people’s ears and noses is cartilage. Sharks have gills, just like other fish. Fish breathe through their gills. People use their lungs to absorb oxygen from the air, unlike fish. Fish use their gills to draw oxygen from the water. Sharks and fish need water to pass over their gills to acquire enough oxygen. Most sharks need to swim in water with a very high current to keep the water moving.
Sharks have many teeth that are placed in multiple rows as opposed to just one row like humans. A new row of teeth progressively fills the space left by the teeth from the outer row when they fall out. A lifetime of tooth loss for some sharks can reach 30,000! Different shark species have different types of teeth. This is because different sharks consume various foods. Plankton is the size of certain shark meal, whereas sea turtles are the size of other shark prey. The majority of sharks do not eat frequently. Weeks may pass between meals for some sharks. Due to their position at the top of the aquatic food chain, sharks are not hunted by other animals. Sharks play a crucial role in preventing out-of-control animal population growth, hence this position is crucial. The diversity, or variety, of life in the oceans, is ensured in part by this mechanism. Sharks have been around for a very long period, which is one of their unique qualities. Since the time of the dinosaurs, some 64 million years ago, sharks have existed in the oceans! Even shark relatives, according to scientists, may have existed 400 million years ago. Sharks are occasionally said to as primitive because they have been around for such a long period and have not undergone much change. Sharks have been a part of the water for an incredibly long time. People may learn a lot about sharks because they are such unique creatures.
Frequently Asked Questions
Question: What is shark skin called?
Ans: Dermal denticles,
Question: Can sharks talk?
Ans: Great whites communicate through their bodies.
Sharks can’t speak, therefore they communicate through body language. Two sharks may “speak” to one another by opening their jaws, nodding their heads, and arching their bodies.
Question: Do sharks have a heart?
Ans: Yes
Question: Do sharks sleep?
Ans: No, but take a few quiet moments.
Question: Do sharks have a tongue?
Ans: Yes
Question: What is shark leather called?
Ans: Shagreen
Question: How old do sharks live?
Ans: 20 to 30 Years