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.

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.