Difference Between Bony Fish and Cartilaginous Fish

Main Difference – Bony Fish vs Cartilaginous Fish

Bony fish and cartilaginous fish are two groups of fish that represent two classes of aquatic chordates. Bony fish belongs to the class Osteichthyes while cartilaginous fish belongs to the class Chondrichthyes. Bony fish can be found in both marine and fresh water. However, cartilaginous fish lives exclusively in marine water. Both types of fish have an endoskeleton. The main difference between bony fish and cartilaginous fish is that bony fish have an endoskeleton completely made up of bones whereas cartilaginous fish have an endoskeleton primarily made up of cartilages.

Key Areas Covered

1. Bony Fish 
     – Definition, Classification, Characteristics
2. Cartilaginous Fish 
     – Definition, Characteristics
3. What are Similarities Between Bony Fish and Cartilaginous Fish
     – Outline of Common Features
4. What is the Difference Between Bony Fish and Cartilaginous Fish
     – Comparison of Key Differences

Key Terms: Actinopterygii, Bony Fish, Cartilaginous Fish, Elasmobranchii, Endoskeleton, Fusiform, Lobe-Finned Fish, Ray-Finned Fish, Sarcopterygii, Teleostomi

Difference Between Bony Fish and Cartilaginous Fish - Comparison Summary

Bony Fish – Definition, Classification, Characteristics

Bony fish refers to a large class of fish distinguished by a skeleton of bone. The divergence of bony fish and cartilaginous fish occurred about 420 million years ago. Around 27,000 species of bony fish have been identified worldwide. Bony fish belong to the class Osteichthyes. They are also known as teleostomi. The largest bony fish in the world is ocean sunfish, which weighs around 2.3 tonnes. The presence of an operculum, a protective covering of the gills, is one of the most significant features of bony fish. Bony fish also possess a swim bladder filled with air for their buoyancy. They have pectoral and pelvic fin pairs. They also possess a single dorsal, anal, and caudal (tail) fins. The rounded and tapered body at the ends is known as the fusiform in bony fish. Bony fish have a lateral line that runs through the body, consisting of a series of sensory organs known as neuromasts. Neuromasts help to sense water pressure and vibrations. Bony fish can see colors.

Two Classes of Bony Fish

The two classes of bony fish are ray-finned fish and lobe-finned fish. 

Difference Between Bony Fish and Cartilaginous Fish_Figure 1

Figure 1: Ray-finned Fish

The fins of the ray-finned fish (Actinopterygii) are composed of webs of skin over the flexible spines. Ray-finned fish have a single dorsal fin. Around 99% of bony fish are ray-finned fish. They live in both marine and freshwater habitats.

Difference Between Bony Fish and Cartilaginous Fish

Figure 2: Lobe-finned Fish

The fins of the lobe-finned fish (Sarcopterygii) resemble stump-like appendages. The fins are also fleshy. Lobe-finned fish have two dorsal fins. Their pectoral and pelvic fins consist of joints that resemble tetrapod limbs. The teeth of lobe-finned fish are covered with a true enamel. The two types of lobe-finned fish are lungfish and coelacanths. Lungfish possess both gills and lungs.

Cartilaginous Fish – Definition, Characteristics

Cartilaginous fish refers to a class of fish with a skeleton made up of cartilages. Around 970 species of cartilaginous fish have been identified worldwide. Cartilaginous fish belong to the class Chondrichthyes. They are also known as elasmobranchii. Cartilaginous fish are exclusively marine. The largest cartilaginous fish is whale shark that weighs 21.5 tonnes. Basking shark, great white shark, thresher shark, rays, skates, and Southern stingray are some examples of cartilaginous fish. The gills of the cartilaginous fish open to the ocean through slits. The mouth of the cartilaginous fish can be found on the underside of the body and the eyes and spiracles occur on the upper side. The skin of the cartilaginous fish is covered with dermal denticles that are pointed in one direction. Generally, sharks eat fish, seals, and whales. Rays and skates eat shrimps, oysters, clams, and crabs. A cartilaginous fish is shown in figure 2.

Main Difference - Bony Fish vs Cartilaginous Fish

Figure 3: Shark

Internal fertilization occurs in cartilaginous fish in which the male uses claspers to grasp the female. Rays are viviparous while skates are oviparous.       

Similarities Between Bony Fish and Cartilaginous Fish

  • Bony fish and cartilaginous fish represent two classes of aquatic chordates.
  • Both bony fish and cartilaginous fish belong to the superclass Pisces.
  • Both bony fish and cartilaginous fish have an endoskeleton.
  • Both bony fish and cartilaginous fish breath through gills.
  • Both bony fish and cartilaginous fish possess a mouth with jaws.
  • Both bony fish and cartilaginous fish have paired fins.

Difference Between Bony Fish and Cartilaginous Fish

Definition

Bony Fish: Bony fish refers to a large class of fish distinguished by a skeleton made up of bone.

Cartilaginous Fish: Cartilaginous fish refers to a class of fish with a skeleton made up of cartilages.

Alternative Names

Bony Fish: Bony fish is also known as teleostomi.

Cartilaginous Fish: Cartilaginous fish is also known as elasmobranchii.

Class

Bony Fish: Bony fish belongs to the class Osteichthyes.

Cartilaginous Fish: Cartilaginous fish belongs to the class Chondrichthyes.

Number of Species

Bony Fish: More than 27,000 bony fish species have been identified worldwide.

Cartilaginous Fish: More than 970 cartilage fish species have been identified worldwide.

Habitat

Bony Fish: Bony fish can be found in both fresh and marine water.

Cartilaginous Fish: Cartilaginous fish can be exclusively found in marine water.

Endoskeleton

Bony Fish: Bony fish has an endoskeleton made up of bones.

Cartilaginous Fish: Cartilaginous fish has an endoskeleton made up of cartilages.

Exoskeleton

Bony Fish: The exoskeleton of bony fish is made up of thin bony plates known as cycloids.

Cartilaginous Fish: The exoskeleton of cartilaginous fish is made up of very small denticles coated with sharp enamel known as placoid.

Position of the Mouth

Bony Fish: Bony fish has a mouth at the anterior tip of the mouth.

Cartilaginous Fish: Cartilaginous fish has a ventrally-positioned mouth.

Oral Jaw Sets

Bony Fish: Bony fish has two sets of oral jaws.

Cartilaginous Fish: Cartilaginous fish has a single set of oral jaws.

Gill Pairs

Bony Fish: Bony fish has four pairs of gills.

Cartilaginous Fish: Cartilaginous fish has five to seven gills.

Operculum

Bony Fish: The gills of the bony fish are covered with an operculum.

Cartilaginous Fish: The gills of the cartilaginous fish are not covered with an operculum.

Air Bladder

Bony Fish: Bony fish has an air bladder known as swimbladder for buoyancy.

Cartilaginous Fish: Cartilaginous fish uses oil-filled liver for buoyancy.

Tail Fin

Bony Fish: The tail fin of bony fish is homocercal.

Cartilaginous Fish: The tail of cartilaginous fish is heterocercal.

Fertilization

Bony Fish: Bony fish exhibits external fertilization.

Cartilaginous Fish: Cartilaginous fish exhibits internal fertilization.

Excretion

Bony Fish: Bony fish excretes ammonia.

Cartilaginous Fish: Cartilaginous fish excretes urea.

Examples

Bony Fish:  Salmon fish, rohu, trout, flying fish, and seahorse are examples of bony fish.

Cartilaginous Fish: Shark, skates, and rays are examples of cartilaginous fish.

Conclusion

Bony fish and cartilaginous fish are two classes of fish classified under the superclass Pisces. The main difference between bony fish and cartilaginous fish is the composition of the endoskeleton in each class of fish. The endoskeleton of bony fish is completely made up of bones whereas the endoskeleton of cartilaginous fish is made up of cartilages.

Reference:

1. Harwood, Jessica, et al. “Bony Fish.” CK-12 Foundation, CK-12 Foundation, 24 Dec. 2016, .
2. “Osteichthyes – Bony Fish” Wildlife Journal Junior, .
3. Kennedy, Jennifer. “What Is a Cartilaginous Fish?” ThoughtCo, .

Image Courtesy:

1. “45910” (CC0) via
2. “Pelvicachromis taeniatus male” by zsispeo via
3. “Grey5b” By Albert kok  via

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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