Chondrichthyes

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Basic Definition of Chondrichthyes

The Chondrichthyes are a group of jawed fishes with a cartilaginous skeleton. Diverse species of fish are included in the class, such as sharks, rays, skates, and chimaeras. Most of them live in the ocean. Osteichthyes fishes are another group of fishes, which are bony fishes.

The Classification of Chondrichthyes

Fishes in the class Chondrichthyes are included in the division Gnathostomata since they have jaws. There are a number of vertebrates with jaws in the Gnathostomata division. There are two superclasses of Gnathostomata, viz. Pisces (with fins) and Tetrapoda (with bare limbs).

Pisces are divided into two classes:

  1. Chondrichthyes- Cartilaginous fishes

  2. Osteichthyes- Bony fishes

Chondrichthyes is subdivided into two subclasses:

  1. Elasmobranchii- Sharks and rays, skates, sawfishes

  2. Holocephali- Chimaeras, also known as ghost sharks.

Kingdom

Animalia

Phylum

Chordata

Subphylum

Vertebrata

Division

Gnathostomata

Superclass

Pisces

Class

Chondrichthyes

Class Chondrichthyes

Chondrichthyes in the Greek language has the following meaning, chondr means ‘Cartilage’ and ichthyes means ‘Fish’. The class Chondrichthyes means a class that contains cartilaginous fishes whose skeleton is composed of cartilage. Chondrichthyes is further subdivided into two subclasses:

  • Elasmobranchii: In Greek, elasmo means ‘Plate’ and branchia means ‘gill’, hence we can tell that long and broad flattened gills are the characteristics of these fishes. It includes sharks and rays, skates, and sawfishes.

  • Holocephali: The word Holocephali means ‘complete head’. It includes Chimaeras, also known as ghost sharks.

Features of the Chondrichthyes

Cartilaginous fish have the following characteristics:

  • Among the Chondrichthyes are powerful jaws that are found in marine fish.

  • Whale sharks, the second-largest vertebrae and the largest fish, measure up to 15 meters in length.

  • They possess a ventral mouth.

  • Calcium deposits provide strength to the endoskeleton, which is composed of cartilage.

  • Notochord can be found throughout life.

  • Besides the elongated upper lobe, the tail consists of two shorter lobes. A distinct heterocercal tail protrudes from the lower lobe as well as the extension of vertebrae into the upper lobe.

  • There are placoid scales covering the skin.

  • Each gill has between five and seven blades.

  • The lack of air bladders means they need to swim constantly to avoid sinking.

  • As poikilothermic animals, they cannot regulate their internal body temperature.

  • In addition to eating other fish, molluscs, and crustaceans, predatory fishes also feed on other species of fish.

  • Two chambered hearts, one with an auricle and one with a ventricle, are present in these creatures.

  • Despite the vertebral column protecting their brains and spinal cords, chimpanzees have developed.

  • The sharks of the Chondrichthyes family possess special sense organs on their heads called electroreceptors that aid them in detecting prey and orienting themselves to their prey.

  • To defend themselves from enemies, they possess poison stings. This also helps the animals to prey on one another.

  • Chondrichthyes digestive system: The stomach, pharynx, mouth, intestines, and cloaca make up the digestive system. In females, the cloaca serves both as a reproductive organ and as an excretory organ.

  • Fertilization occurs internally. They are oviparous in some cases and viviparous in others.

The General Characteristics of Chondrichthyes and Osteichthyes

Chondrichthyes and Osteichthyes have the following general characteristics:

  • They both belong to the phylum Pisces. 

  • Both have endoskeletons and exoskeletons.

  • Both breathe through the gills.

  • Both have jaws and paired appendages.

  • It is possible for them to be oviparous, viviparous, or ovoviviparous.

According to the structure of the endoskeleton, Pisces has two types of classes: the Chondrichthyes and the Osteichthyes. Both freshwater and marine species fall into these classes. Humans depend on fishes for nutrition and micronutrients, which play a very important role in their diet as they control most diseases. Fish is not just crucial to the ecosystem but is also very important to us as it provides the body with many nutrients and micronutrients. Nutrition is crucial to children's physical and mental development. People living in coastal regions of many developing countries rely heavily on them for income and employment.  

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FAQs (Frequently Asked Questions)

1. Write the difference between Chondrichthyes and Osteichthyes.

Characters

Chondrichthyes

Osteichthyes

Endoskeleton

Cartilaginous endoskeleton

Bony endoskeleton

Size

Large body

Smaller in size compared to Chondrichthyes

Position of mouth

Ventrally

Terminal

Scales

Placoid scales are present

Cycloid scales are present

Number of gills

Five to seven pairs of gills are present excluding the operculum.

Four pairs of gills are present including the operculum.

Excretory waste

Urea

Ammonia

Jaw

Has a single set of jaws

Two sets of jaws are found.

Fertilization

Internal fertilization

External fertilization

2. Why do Sharks consider Cartilaginous Fishes?

Sharks, skates, and rays all of these fishes have cartilaginous Skeleton because the density of the cartilage is very less which helps the sharks to move faster in the water without the use of more energy and keeps them afloat. As the density of the cartilage is less as compared to the bones it provides more flexibility and hence they can bend easily as compared to the bony fishes.

3. Write down the characteristics of Cartilaginous Fish.

The characteristics of cartilaginous fish are as follows:

  • The endoskeleton is made up of cartilage.

  • They have paired gills and fins.

  • The heart is two-chambered.

  • The body is covered by placoid scales.

  • The fertilization takes place internally.

  • They lack a swim bladder.

4. What are Some Chondrichthyes?

Here are a few Chondrichthyes examples:

  • Sharks: Dogfish, Whale shark, Angel shark, Ground Shark, etc.

  • Rays: Electric ray, Stingray, Manta ray, etc.

  • Skates: Little skate, Small deep-water skate, Andaman leg skate, etc.

  • Sawfishes: Narrow sawfish, Dwarf sawfish.

5. What is the Reproduction Process of Chondrichthyes?

Fertilization takes place internally. The development is usually through live birth (ovoviviparous species), but it can also be through eggs (oviparous species). There are also rare viviparous species. Some chondrichthyans guard their eggs after birth, but there is no parental care.

6. Do Cartilaginous Fishes Differ from Bony Fishes in Any Way?

Having skeletons predominantly composed of cartilage is characteristic of cartilaginous fish, while having skeletons mostly composed of bone is characteristic of bony fish. In addition, these two types of fish are classified under different taxonomic groups - the cartilaginous fish fall into the class Chondrichthyes and the bony fish into the superclass Osteichthyes.

7. How do Chondrichthyes eat?

Their blunt teeth allow them to eat mostly fish and invertebrates. They also eat plankton and other small organisms. In addition to sharks and rays, nearly everything that swims is prey for both animals.

8. What are the Economic Benefits of Chondrichthyes?

Rays are worth an economical amount. Rays are marketed for food in many countries around the world, primarily in Europe and Asia, with about 126,000 short tons (roughly 114,000,000 kilograms) being marketed for food. In the local market, scaleless species' skins are used for drumheads, while scaly species' skins are made into shagreen

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