Petromyzon (Lamprey)

COMMENTS :

1. Commonly known as Lamprey.

2. It leads an ectoparasitic life on fishes.

3. Body is eel like differentiated into head, trunk and tail.

4. Head region is characterised by buccal funnel.

5. Mouth is circular with numerous horny teeth.

6. Paired eyes are large and functional

7. Seven pairs of external gill apertures are well developed.

8. Two dorsal fins and one caudal fin present.

9. Found in fresh water as well as in sea.

10. Lampreys have posed a great economic problems to the fisheries in some regions.

11. They destroy valuable fish by feeding on their blood and body fluids.

12. Control devices have not been wholly effective.

COMMENTS :

1. Exclusively marine and commonly called as Dogfish.

2. Body is long, pointed at both ends and laterally compressed.

3. Body is divisible into head, trunk and tail.

4. Head is dorso ventrally compressed.

5. Crescentic mouth situated on the ventral side of the head.

6. The external nostrils lying one on each side of the mouth.

7. Five pairs of gill slits are present for respiration.

8. The large pectoral fins originate from behind the gill clefts.

9. In male each pelvic fin bears clasper.

10. The cloacal aperture opens between the two pelvic fins.

COMMENTS :

1. Labed is most popular carp of fresh water commonly known as Rohu.

2. It is found in ponds, rivers, lakes and prefers clean water and respires by means of gills.

3. It is chiefly herbivorous and a bottom feeder eating algae and aquatic plants.

4. Body is spindle shaped, elongated and laterally compressed.

5. The body is divisible into head, trunk and tail. Head extends from tip of snout to hind edge of operculum.

6. It frequantly comes to water surface to take air into the air bladder.

7. It is oviparous and breeds in running water in July and August.

8. Trunk and tail are covered by thin, rounded, overlapping dermal cycloid scales.

9. Mouth is transverse and semioval. Barbels are present.

COMMENTS :

1. It is found in Burnett and Mary rivers in Queensland, Australia.

2. It is commonly known as Australian lung-fish or Burnett salmon.

3. Body is elongated and compressed measuring about one to two metres.

4. Scales are large, thin and covered with spines.

5. Paired fins are rather leaf-like or paddle-like.

6. Caudal fin is symmentrical and pointed.

7. Dentral plates are oval crescentic or triangular terminating in a smooth or feebly denticulated biting margins.

8. Lower jaw with a small toothless dentary on each side.

9. Branchial arches are five in number and bisegmented.

10. The first four branchial arches carry holobranchs.

11. Air-bladder is single and the lateral line system is somewhat degenerated.

12. Inactive and sluggish in habit, usually lying motionless on the bottom.

13. Carnivorous. Feeds on fresh water crustaceans, worms and molluscs.

14. Lung fishes are large fishes inhabitating semi-permanent fresh waters and swamps in Africa, S. America and Australia.

Features of Petromyzon, Study of Petromyzon, Comments on Petromyzon