What are Ray-Finned-Fishes?
Introduction:
Ray-finned fishes are the biggest class of fishes, also called Actinopterygii. From the early Devonian Era, they existed for 400 million years ago. This class comprises 42 orders of fish including more than 480 families. Almost 80 species are explored from the fossil record.
Actinopterygii word is derived from the Greek language from “actino- having rays”, and “ptérux-wing or fins”. And the ray-finned are called so because their fins are of the web of skin and reinforced by horny or bony spines called rays and this feature opposes the lobe-finned fishes having fleshy and lobed fins. These fin rays are attached directly to the basal skeletal elements and the radials which make the support and connection between the fins rays and the internal skeleton like pectoral girdles and pelvic.
Classification :
Kingdom: Animalia
Phylum: Chordata
Super-Class: Osteichthyes
Class: Actinopterygii
Characteristics:
The ray-finned fishes are present in many different forms. The main characteristics of a standard ray-finned fish are :
dorsal fin
fin rays
lateral line
kidney
swim bladder
Weberian apparatus
inner ear
brain
nostrils
eye
gills
heart
stomach
gall bladder
spleen
internal sex organs (ovaries or testes),
ventral fins
spine
anal fin
tail (caudal fin)
external genitalia
The presence of a swim bladder is the more specific structure of this class. These fishes have many different types of scales but the most advanced actinopterygians named all teleosts have scales that are leptoid scales. The outer side of these scales fans is out with bony ridges and the inner part is connected with fibrous connective tissue. The leptoid scales are slimmer and are more transparent as compared to all other scales, also they lack the dentine-like layers which hardened the enamel of many other fish. Ganoid scales are found in non-teleost actinopterygians, As the fish grows and becomes large in size new scales are added in concentric patterns.
Both the “Ray-finned and lobe-finned fishes”, including all the tetrapods develop lungs used for aerial respiration instead of other mechanisms for respiration.
According to the arrangement of fin rays and body shape following are the type of fishes:
Tuna
Swordfish
Cod
Flat-fish
Lanternfish
Elongated bristlemouth
Fang-tooth
Angler-fish
Alfonsino
Giant oarfish
European conger
Hawaiian turkey fish
Benthic batfish
Deep sea eel
Freshwater elephant fish
Sturgeon Acipenser
Ambush predator
Sea-horses
Mirror dory
Mahi Mahi
Mola tecta
Flying fish
Jurrasic
Evolutionary Behaviour:
Ray-finned fish has undergone many changes in their jaws through their evolution. Primitive forms had simple jaws with weak jaw-closing muscles used for snapping the prey but they evolved their jaws to catch and grab prey with a firm grip, helping them to find their feed easily.
The main group of living ray-finned fishes, the actinopterygians, include their evolutionary relationships to other types of groups of fishes and the tetrapods having four-limbs called tetrapods.
The later species include mostly terrestrial organisms but also include groups that became secondarily aquatic organisms like Whales and Dolphins. Tetrapods emerged in Devonian Period from a group of bony fishes.
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