Chondrichthyes - Definition, Classification, Characteristics, Examples & Facts

The Chondrichthyes is a class of vertebrates commonly known as cartilaginous fishes, having skeletons made primarily of cartilage rather than bone. These species have five to seven pairs of exposed gill slits on each side of their head, paired fins, hard scales, and a two-chambered heart. The absence of bone is a derived trait, as they descended from bony ancestors, with only their teeth and sometimes vertebrae containing calcium. They are an important part of Phylum Chordata and Subphylum Vertebrata under Superclass Pisces.

This Story also Contains

1. Chondrichthyes Classification
2. Chondrichthyes Characteristics
3. Chondrichthyes Examples
4. Ecological Importance of Chondrichthyes

Cartilaginous fishes are primarily marine and have evolved from about 400 million years back. Chondrichthyes play a central role in maintaining the health and biodiversity of Aquatic ecosystems. This article covers the Chondrichthyes classification and their characteristics, highlighting their unique adaptations that differentiate them from other fish classes.

Chondrichthyes Classification

The chondrichthyes are placed under Vertebrata, where the notochord is present throughout life, and the skeleton remains cartilaginous instead of forming a bony vertebral column.

Chondrichthyes are divided into these subclasses:

1. Elasmobranchii (sharks, rays, and skates)

• It has predatory and streamlined bodies with skeletons made of cartilage, many rows of teeth, and electroreceptive organs.

• Examples: Great White Shark, Manta Ray.

2. Holocephali (chimaeras)

• Unique, rabbit-like faces with specialised dental plates; single gill opening.

• Examples: Ratfish, Ghost Shark.

Also Read:

• Osteichthyes

• Animal Kingdom

• Phylum Platyhelminthes

Chondrichthyes Characteristics

• The skeleton is composed of cartilage instead of bone, providing flexibility and durability.

• The tooth-like overlapping scales help reduce drag, hence improving swimming efficiency.

• It has different fin shapes that allow for stability and survival.

• No swim bladder, yet buoyancy is maintained by large livers filled with oil.

• Respiration: Efficient oxygen extraction from water is possible through the gill slits while some species with spiracles, which are respiratory organs usually used while resting on the ocean floor.

• Control of buoyancy: The liver stores oil changes to maintain buoyancy.

• Osmoregulation: Ability to maintain constant internal salt concentrations in various marine environments.

Reproduction

1. Oviparous: The eggs are laid outside and develop outside the female's body, e.g., skates.

2. Ovoviviparous: The eggs hatch inside the female body, and are born live. Example: Most sharks.

3. Viviparous: Embryos develop inside the female. They get nourishment directly from the mother. Example: Some sharks.

Chondrichthyes Examples

The prominent examples of cartilaginous fishes are:

Rays

• Torpedo (Electric ray)

• Narcine bancroftii (Lesser electric ray)

• Trygon (Stingray)

• Manta (Manta ray)

Sharks

• Rhincodon (Whale shark)

• Scoliodon (Dogfish)

• Charcarodon charcharias (The great white shark)

Sawfishes

• Anoxypristis cuspidata (Narrow sawfish)

• Pristis clavata (Dwarf sawfish)

Skates

• Cruriraja andamanica (Andaman leg skate)

• Leucoraja erinacea (Little skate)

• Gurgesiella (Small deepwater skate)

Chimaeras

• Callorhinchus milii (Australian ghost shark)

• Hydrolagus alphus (Whitespot ghost shark)

• Chimaera argiloba (Whitefin chimaera)

Ecological Importance of Chondrichthyes

• Chondrichthyes are top predators in regulating prey populations, hence maintaining ecological balances, and their effects eventually lead to biodiversity and the stability of ecosystems.

• Their protection comes with sustainable fishing methods and protected marine areas as part of conservation efforts.

• They are also challenged by overfishing, bycatch, habitat loss, and pollution.

• Chondrichthyes are economically relevant through fisheries and, more recently, by ecotourism activities such as shark diving.

• Understanding shark behaviour minimises human–shark conflicts in such a way that safety is well-balanced against conservation.

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