ACIPENSER : STURGEON

Contents hide

1) ACIPENSER : STURGEON

1.1) CLASSIFICATION OF ACIPENSER : STURGEON

1.2) GEOGRAPHICAL DISTRIBUTION

1.3) HABIT AND HABITAT

1.4) GENERAL CHARACTERSTICS OF ACIPENSER : STURGEON

1.5) Economic importance

1.6) SPECIAL FEATURES

1.7) IDENTIFICATION

CLASSIFICATION OF ACIPENSER : STURGEON

Phylum :- CHORDATA ( Notochord and dorsal tubular nerve cord present and gill-slits present).
Group :- CRANIATA ( Cranium with brain present ).
Subphylum :- VERTEBRATA (Vertebral column present ).
Division :- GNATHOSTOMATA ( Jaws and paired appendages present ).
Super class :- PISCES (Paired fins , gills and skin with scales)
Class :- OSTEICHTHYES (Bony fishes).
SUB-CLASS :- PALAEOPTERYGII (Ancient fIshes).
Order :- CHONDROSTEI (Body covered with bony scutes or naked. Tail heterocercal. Skeleton largely cartilaginous. Notochord unsegmented. Vertebrae acentrous).
FAMILY :- POLYODONTIDAE
GENUS :- Acipenser

GEOGRAPHICAL DISTRIBUTION

Acipenser is abundantly distributed in Black Sea, Sea of Azor, Caspian Sea, in rivers of Europe, China and on the Atlantic coasts of North America.

HABIT AND HABITAT

Acipenser is a marine, bottom-dwelling fish. They stir the bottom with their snout in search of small invertebrates, worms, molluscs, small fishes and aquatic plants for feeding. They are migratory fishes, anadromous, ascending rivers for spawning.

GENERAL CHARACTERSTICS OF ACIPENSER : STURGEON

Commonly known as Sturgeon, measuring 2 to 4 metres in length.
Body is elongated, cylindrical and bulky and is divided into head, trunk and tail. In the body scales are represented by five longitudinal rows of bony scutes with small intervening ossification. Each plate is provided with a pointed and partly-conical and backwardly-directed spine.
Head is produced ahead as a long flattened rostrum or snout. It contains a pair of eyes and functional spiracles.
Well developed rostrum with 4 ventral barbels is used to stir the bottom mud in search of small invertebrates. Barbels detect the food and direct the rostrum to dig the mud. Food is sucked through the ventral surface of the snout.
Mouth is ventral and transverse and without teeth in jaws.
Narrow crevices between scutes contain dermal denticles like those of Elasmobranchi.
Spiracles open and skeleton cartilaginous. Operculum represented by opercular bone. Dorsal fin single and posteriorly placed. Paired fins are pectoral and pelvic fins. Ventral fin opposite to dorsal fin. Caudal fin bilobed.
2 to 3 million eggs are laid by a single fish during the breeding season. The air bladder is smooth, oval and contains ciliated epithelium.

Economic importance

Black eggs of European sturgeons are used to prepare a delicacy called as caviar. Their air bladder is used to prepare isinglass meant for cleaning wines and beers.

SPECIAL FEATURES

Acipenser shows combination of primitive and secondary modified characters. They resemble elasmobranchs in having open spiracles, heterocercal tail, mostly cartilaginous skeleton, spiral valve in the intestine and conus arteriosus. Loss of bone shows secondary character and presence of rhomboid scales shows its affinity with ganoid fishes.