Bony Fish

Bony fish is popularly known by its scientific name as Osteichthyes fish. Bony fish meaning is a group of fish whose skeletons are mainly made of bony tissues. The bony fish class is made up of Sarcopterygii class, that is, lobe-finned fishes, and Actinopterygii class, that is, ray-finned fishes in the vertebrate subphylum. This group also includes a large population of the world’s living fishes. They do not include the jawless fishes of the Agnatha class and the cartilage fishes of the class Chondrichthyes. They have a swim bladder which helps them in giving the required buoyancy, bony plate-like scales, gill chamber is covered by the gills, and they fertilize eggs externally. 

Bony fishes occur everywhere, including freshwater, oceans, caves, vents, thermal springs, etc. They occur in a large variety of shapes. The body size can range from 0.5 inches, that is, 12 mm to 15 feet, that is, 4.5 meters, and can weigh more than a tonne. 

Bony Fish in The Animal Kingdom

In the biological classification system, all the living creatures are classified into two kingdoms- plant kingdom and animal kingdom. The animal kingdom has a total of 12 phyla. The Chordata phylum has five classes- fishes, amphibians, reptiles, Avis, mammals. Bony fish is an animal of the fish class. The clade is Teleostomi and the superclass is Osteichthyes. The scientific names are different for different species of bony fish. All of them are cold-blooded vertebrates. Some examples of bony fish are lungfish, catfish, salmonids, clownfish, tuna, cichlid, anglerfish, sturgeons, eels, flatfish, etc. 

Classification Characteristics of Bony Fishes

Every living creature is classified in the biological classification system depending on its classification characteristics. They are placed in particular phyla and classes. Bony fish are placed in the Chordata phylum and the fish class for their classification characteristics. These characteristics of bony fish are mentioned below.

• Their entire body is covered with ctenoid scales. 

• Their tails are homocercal. 

• Bony fish skeleton is structured with bones.

• They have mucus glands in their skin.

• They have odd and even fin rays. 

Description of Bony Fish

The body shape of bony fish differs from different species. Most of them have a roughly cylindrical body with tapering at both ends. This body shape helps in consuming less energy while swimming. The size of the bony fish can be from 9 mm to 11 meters. The size of the small bony fish is 9 to 15 mm (0.6- 0.4 inches). Large bony fishes can be larger than a human also. The largest bony fish, Regalecus glesne, is 36 ft long. The weight of bony fish can be up to 2300 kgs. The size and position of the head depending on the habitat of the species. The size and position of the eyes are according to their living and swimming processes. 

Bony fish has a pigmented body colour. The body colour depends on the species of the bony fish. The pigmentation is produced by the chromatophore cells. The colour can be changed by the reflective cells. As the different depths observe different wavelengths, the body colour depends on the depth of the water also. Some of the bony fishes can blend their body colour by changing their pigmentation. Some bony fishes show disruptive colouration. Bony fishes have even and odd fin rays. They show different degrees of fin fusion and reduction. Some bony fishes have flexible and soft fin rays. Others have rigid and spiny fin rays. Some of them have venom glands in their fin rays. Bony fishes have four types of scales- ctenoid, cycloid, ganoid, cosmoid.

[Image will be Uploaded Soon]

Food Habit of Bony Fish 

The food preferences of bony fishes differ from different species. They can be herbivorous, carnivorous, omnivorous, detritivorous, etc. Some common food preferences of different bony fish species are marine snails, annelid worms, squids, mussels, clams, crustaceans, birds, insects, amphibians, other fishes, and small mammals, etc. The food preferences and the food quantity depend on the size of the bony fish. The metabolic rate depends on the amount of food and the temperature of the environment. Smaller bony fishes have a metabolic rate. The bony fishes living in a warm temperature need more food than the bony fishes living in cold water. Some of the bony fishes can survive without eating food for a long time. Many bony fishes are active predators. Some bony fishes are filter feeders. 

Habitation of Bony Fish

Like other fishes, bony fishes live in water bodies. They live in a fresh and brackish environment. Generally, they are found in the sea or oceans. The salinity of the environment differs from different species of bony fish. Some bony fishes live in the open oceans. Some others are adapted for living along the bottom. Apart from the large water bodies, there are some other habitats of the bony fishes. They can be found in rivers, lakes, streams, kelp forests, rocky shores, ponds, etc. Also, some bony fishes are found in the deserts, caves, dried ponds, etc. 

Types of Bony Fish

Osteichthyes class, that is, the bony fish class was recognized by its swim bladder, three pairs of gill arches, and a bony skeleton. Later, this was subdivided into two full classes of Sarcopterygii and Actinopterygii. Most of the bony fishes belong to the Actinopterygii class. Let's move into the details of classification.

Actinopterygii: They are the ray-finned fishes and the group divided from the bony fishes. They are so-called because they possess fin rays called lepidotrichia. Their fins are part of the flesh that are supported by bony spines. The fins are attached to their pelvic and pectoral girdles, that is, their basal and proximal skeletal elements, the radials, which show the connection between the internal skeleton and fins. Actinopterygii is mostly vertebrates, which numbers more than 95% of the total bony fish species. They are present in all kinds of environments including freshwater and oceans. A part of this class is present in oceans which are referred to as marine bony fish. Size and shapes are varied, ranging with a huge difference in numbers. They possess a single dorsal fin.

Sarcopterygii: They are the lobe-finned fishes that also possess lepidotrichia as fleshy, lobed fins. The lobes are attached to the skin by a single bone. Previously, this class excluded Tetrapoda, which is a group of terrestrial vertebrates. Now, the class Sarcopterygii includes tetrapods, lungfish, and coelacanths. Their fins differ from all other fishes, based on their structure. The pectoral and pelvic fins have evolved into legs of the land tetrapods vertebrates. This class possesses two dorsal fins. This class possesses a hinge line as a braincase but it is absent in lungfish and tetrapods. All the fishes consist of teeth covered with enamel.

Comparison Between Bony and Cartilaginous Fish?

Answer: Cartilage fishes consist of a wide variety including rays, chimeras, and sharks. In the table below, we shall compare sharks with bony fishes.

Did You Know?

Now, We Are Going to Discuss Some Unknown Facts About Bony Fish.

• There are about 21000 species of bony fish available in the world. 

• Almost all the bony fishes have an ossified endoskeleton with a hardcover of calcium phosphate.

• Bony fishes have gills. For the majority, it is their sole respiratory organ. Others can complete their respiration through the swim bladders or lungs. 

• The swim bladders present in their body help to maintain a neutral balance between floating and sinking.  

• Unlike other fishes, bony fishes can see in colours. 

• One of the most primitive types of bony fish is Coelacanths. Their fossils can range up to 60 million years ago. 

• 300 million years ago, some of the bony fishes had intermediary traits towards the amphibians. 

• Above 1000 species of bony fish can produce bioluminescence. 

• Though they have large eyes, they cannot see clearly because of their rudimentary retina. 

• A bony fish called the scorpion has more powerful venom than a cobra.

Conclusion

Bony fishes are the Osteichthyes of the fish class. There is no specific bony fish scientific name. Bony fish are a large range of species in the world. They have a huge variety of species. They are different in body colours, size, height, weight, etc. Their habitats and food habits differ from different species. All the bony fishes are divided into two groups- Actinopterygii and Sarcopterygii. Going through all the features of these two groups, we can have a good knowledge of bony fish and determine any non bony fish.