CLASSIFICATION of PRISTIS : SAW FISH

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 :-  CHONDRICHTHYES { =ELASMOBRANCHI } (Endoskeleton cartilaginous. Scales usually placoid. spiral valve in intestine ).

Sub-class :- SELACHI (Sharks and rays. Gills in seperate clefts. Cloaca present).

Order :- HYPOTREMATA { = BATOIDAE } (Gills-slits ventral. spiracles present. dorsal fin on tail, if present)

Family :- PRISTIDAE

Genus :- Pristis 

GEOGRAPHICAL DISTRIBUTION

Pristis is reported from America, Gulf of Mexico, Lower Mississippi, the Mediterranean sea and Atlantic waters.

HABIT AND HABITAT

Pristis is a warm water marine predacious fish feeding on small fishes and other marine animals by slashing them with its saw. It often ascends the river.

pristis : saw fish

GENERAL CHARACTERSTICS OF PRISTIS : SAW FISH

  • Commonly called as saw fish, weighing 150-500 kg and measuring 3 to 6 metres in length.
  • Body shape is midway between a shark and a ray. The anterior part is Flattened dorsoventrally and is ray-like while the posterior part, for more than hall is shark-like. It exhibits close relationship with rays.
  • Elongated, shark like body is slightly depressed and divided into head, trunk and tail.
  • Head contains a pair of eyes and a pair of spiracles behind the eyes. Water passes through the spiracles and goes out through the gill-slits.
  • Mouth ventral.
  • Snout is anteriorly produced into a saw-like rostrum with large and small weakly embedded teeth.
  • Dorsal fins are large. First dorsal fin is opposite to pelvic fin. Second dorsal fin is called adipose fin. Paired fins are pectoral fin and pelvic fin. Tail contains heterocercal caudal fins.
  • Sawfishes are ovoviviparous fishes (that is, fertilized eggs grow within the body of female sawfishes, and the young are born alive) whose litters average eight young.  
  • Sawfishes are not generally considered dangerous, but their saws (or rostrums), constituting as much as one-third their total length, can be formidable. The saws are used in feeding, in digging out bottom animals, and, when lashed about, in killing or maiming schooling fishes.

ECONOMIC IMPORTANCE

Economic importance : The fish is also economically very beneficial as its liver oil is rich in vitamin value and its skin used for making scale boards.

SPECIAL FEATURES

The important structure is ‘saw-like snout, formed by the elongation and Flattening of head and skull. They are flattened in the form of a rostrum, which contains a series of tooth-like 16 to 32 pairs of teeth on the lateral margins. Teeth are fixed in sockets, in the calcified rostral cartilage, Rostrum acts as an organ of offence and defence. Pristis is capable for retaining urea in fresh-water while ascending in rivers. 

IDENTIFICATION

Since this fish has saw-like toothed snout and above features, hence it is Pristis.

PRISTIS : SAW FISH
PRISTIS : SAW FISH

REFERENCES

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