Cartilaginous Fish (Chondrichthyes):
Cartilaginous fishes belong to the Chondrichthyes class that includes the sharks, skates, and rays, and the other course includes chimeras.
These are the vertebrates whose internal skeleton is made of cartilage, and these species contain no bones. Cartilaginous fishes have one or two dorsal fins, a caudal fin, anal fins, and ventral fins. Other than their distinctive feature of the skeleton, these fishes have gills that open through slits. Although different species may carry different gill slits, the other characteristics also include scales and two-chambered hearts.
Cartilaginous Fish Characteristics:
The cartilaginous fishes do not have bone marrow (a semi-solid tissue found in the portion of bones), red blood cells are produced in the spleen (a particular tissue around the reproductive organ). These fishes have tough skin covered with dermal teeth, also called placoid scales.
Rather than gills, these species can also breathe through their spiracles that can be found behind each eye. Spiracles are small openings that allow cartilaginous fishes to draw oxygen from the water from the top of their head, which also will enable them to breathe while resting at the bottom of the water.
The class Chondrichthyes is divided into two sub classes-
- Elasmobranchii- that includes sharks, rays, and skates.
- Holocephali- that includes chimeras.
Sharks, rays, and skates have five slit gills, a spiracle behind each eye, a toothed jaw, and dermal teeth on the upper body while the chimeras have gill opening on each side, tooth plates and a skull attached with the upper jaw.
Cartilaginous Fish Facts:
- Cartilaginous fishes do not have swimming bladders, so they have to maintain a swimming motion continuously even when they are sleeping, or else they will sink into the bottom.
- The swimming motion of rays is unique from the swimming motion of sharks as rears have a flattened body and rear spine. Unlike rays, the chimeras use their pectoral fins while swimming.
- The fertilization is internal in all the cartilaginous fishes, some species are egg layers, and some species hatch the eggs within the female and gives birth to live young.
The Bony Fish (Osteichthyes):
Bony fish are the species of fishes that belongs to the Osteichthyes super-class, the skeleton of these fishes are made up of bone tissues. The bone tissues serve as the same function that the bones of a human serve. Bony fishes also breathe through gills, but their gills are covered with a hard thin plate called an operculum.
Bony Fish Characteristics:
The species of bony fishes subdivided into two classes-
- Ray-finned fish
- Lobe-finned fish
- Ray-finned fishes can be found in all aquatic oceans, these species have enlarged pectoral fins and meld pelvic fins.
- On the other hand, the lobe-finned fishes have a central axis of bone that acts as a skeletal support for fins and limbs; their upper jaw is combined with their skulls.
- The bony fish is the largest group of vertebrates that are existing today. The head and the pectoral girdles are covered with bones that are derived from the skin.
- The swimming bladder helps the bony fishes to balance their body between sinking and floating.
- Bony fishes perform external fertilization, where the females release thousands of eggs in water, and the male releases sperms to fertilize the eggs.
- Not all the species of bony fishes lay eggs, some give birth to young ones. Under the IUCN, these species classified as vulnerable.
Difference Between Bony Fish and Cartilaginous Fish:
|Parameters||Bony fish||Cartilaginous Fish|
|Scientific name-||The scientific name of the bony fish is Osteichthyes.||The scientific name of the cartilaginous fish is Chondrichytes.|
|Habitat-||Cartilaginous fish habitat:|
Cartilaginous fish can be found in the water bodies across the world. They habitat in the shallow sandy bottom of the ocean and can live in open water.
|Bony fish habitat-|
Bony fish can be found in waters all around the world, in fresh and saltwater. They can live in the oceans from shallow to deep water in cold and warm temperatures.
|Species-||Cartilaginous fish species-|
Cartilaginous fishes include sharks, rays, skates, and chimeras. There are nearly 600 species of rays and skates and around 500 species of sharks.
|Bony fish species- |
Bony fishes are the most diverse vertebrates with over 20,000 species.
|Size-||The species of cartilaginous fish ranges from 6.3 inches to 50 feet whale shark.||The species of bony fish can be below a half-inch to 26 feet.|
|Diet-||The species of cartilaginous fish feed on a variety of food, sharks, can eat marine mammals such as whales and may also eat seals, whereas rays and skates feed on crabs, clams, oyster and shrimp.||The diet of bony fish includes plankton, crabs, green sea urchins, and other fishes. Some species of bony fishes are omnivorous who feeds on aquatic animals and plants.|
|Lifespan-||Cartilaginous fish can live up to 50 to 100 years.||The lifespan of bony fishes ranges from a few months to 100 years.|
Cartilaginous Fish vs. Bony Fish:
The main difference between cartilaginous fish and bony fish is:
- The cartilaginous fish consists of cartilages, whereas the endoskeleton of bony fish consists of bones.
- Bony fish can found in both fresh and saltwater, but cartilaginous fish only inhabit the marine water.
- Cartilaginous fish have 5 to 7 pairs of gills; bony fishes have 4 pairs of gills.
- Swim bladders are present in bony fish and absent in cartilaginous.
- The excretory system of cartilaginous fish is urea, whereas, in bony fish, it is ammonia.
- The mouth of cartilaginous fish is ventral and the mouth of bony fish is anterior.
- The tail of cartilaginous fish is heterocercal, whereas the tail of bony fish is homocercal.