CLASSIFICATION OF POLYPTERUS BICHIR
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 :- PALAEOPTERGII (Ancient fishes. Dermal fin rays numerous. Clavicles present. Nostrils free from mouth cavity.)
Order :- CLADISTIA (Body slender, scales thick, rhomboid, enamelled. Air bladder lung like).
FAMILY :- POLYPTERIDAE (Pectoral fins lobate, while pelvic fms non-lobate)
GENUS :- Polypterus
SPECIES :- bichir
Polypterus is restricted to tropical Africa, the Nile, Nigeria and Congo.
HABIT AND HABITAT
Polypterus is found in sea water. It becomes active during night. It feeds on small teleosts, batrachians and crustaceans.
GENERAL CHARACTERSTICS OF POLYPTERUS BICHIR
- Polypterus is one of the most primitive living bony fish and could be easily regarded as living fossil. Body divisible into head, trunk and tail.
- Body is elongated, cylindrical, measuring 1 metre in length and covered with rhombic ganoid scales.
- Surface covering consists of a thin shiny enamel called ganoin.
- Head is covered with a horny shield containing tubular nostrils and forwardly lying eyes.
- Spiracles present.
- There is a fleshy lip on the lower jaw matching that of the upper jaw.
- Dorsal fin consists of a series of 5 to 18 isolated finlets composed of single spine-like scales to which are attaches! one or more soft rays.
- Pectoral fins, found behind head, are broad rounded and lobed at bases. Ventral rm backwardly situated. Pelvic fins present. Caudal fin diphycercal.
- Larva possesses plume-like external gills, attached to the hyoid arch, resembling the gills of Amphibian larva.
- Polypterus shows combination of primitive and advanced characters. Primitive characters are non-overlapping scales, spiracle, certain skull bones and their arrangement, spiral valve in intestine and the superficial resemblance of paired fins to broad-based crossopterygian fins. It has also advanced features like dorso-lateral position of nostrils, pyloric caecum in the gut and similar urinogenital system, which bring them closer to bony fishes. The tail is no longer heterocercal. The air bladder though connected with pharynx seems to be respiratory organ but remains non-functional as Polypterus cannot live outside water for a longer period.
- This fish has dorsal finlets and above features, hence it is Polypterus.