The word Actinopterygii is formed from the Greek word actis meaning rays, pteryx meaning fin. Actinopterygii means ray-finned. Ray-finned fishes are known as Actinopterygii. About 96% of living fish belong to this category. They are 10 mm to 4 m long and weigh 1500 kg. Their number of species is 31,045. 12 classes, 48 tribes and 253 species of this class have been identified in the fresh water of Bangladesh.
Characteristics of Actinopterygii
1. Their endoskeleton is made up of bones.
2. Body covered with cycloid, tinoid and ganoid scales. Some fish do not have scales. Such as- horn, Magur etc. Dr. Siddiq Publications
3. All body fins are bony and have dermal rays (lepidotrachea).
4. Their gills are covered with kanko.
5. Caudal fin homocircular type. That is, the tail fin is divided into two equal parts.
6. Their mouth is located at the tip.
7. Their brain consists of cerebellum, optic lobe and cerebrum.
8. There are 10 pairs of carotid nerves in the body.
9. The reproductive organs consist of four pairs of gills. On both sides of the head, there is a flower opening. Dr. Siddiq Publications
10. Air sacs are present in the body.
11. They breathe and float with the help of crackers.
12. Their heart is two-chambered and known as the venus heart.
13. They are unisexual animals. Excretion occurs. Direct and indirect effusion is observed.
[key words to remember features: endoskeleton, cycloid, tenoid, ganoid, cutaneous ray, conch, homocercal, pore, brain, carotid nerve, gill, air sac, heart]
Some fishes of the class Actinopterygii
Ilisha- Tenualosa ilisha
Roe – Labeo rohita
Catla- Catla catla
Taki fish – Channa punctatus
Magur fish – Clarias batrachus
Boal- Wallago attu
Queen fish – Botia dario
Tuna fish – Thunnus albacares
Where fish- Anabas testudineus
Chital fish- Notopterus chitala
Pangasius fish – Pangasius pangasius
Cirrhinus cirrhosus
Bombay Dak/Lytra fish- Harpadon nehereus
Sturgeon fish – Acipenser oxyrhynchus
Paddle fish – Polyodon spathula
Horn fish – Heteropneustis fossilis
Sunfish – Mola mola
Cat fish
Those fishes that have barbs around their mouth like cat’s whiskers are called cat fish. Catfish belong to the class Actinopterygii. For example, horn fish, magur fish etc. Dr. Siddiq Publications
Homocercal
If two segments of the caudal fin of a fish are equal, it is called homocircular. Fishes of the class Actinoterygii have homocercles. For example – Ilisha (Tenualosa ilisha).
Cycloid scale
Fish scales that are round or oval, with growth lines and smooth edges are called cycloid scales. The inner part of the rib is called the anterior part, the outer part is called the posterior part and the two side parts are called the lateral parts. The tip has longitudinal grooves or radii. For example – Labeo rohita. Dr. Siddiq Publications
Cteoid scale
The cartilage in bony fish is called tinoid cartilage. Its posterior margin is finely barbed. For example – Anabas testudineus.