CLASSIFICATION OF PETROMYZON OR LAMPREY
Subphylum :- VERTEBRATA (Vertebral column present ).
Division :- Agnatha ( Jaws and paired appendages absent ).
Class :- Cyclostomata ( Mouth circular, suctorial, without jaws ).
Order :- Petromyzontia (Mouth with funnel, without tentacles. Nasopharyngeal pouch blind. Gills 7 pairs, open independently to exterior. Branchial basket well developed ).
GENUS :- Petromyzon
SPECIES :- marinus
Petromyzon marinus is found in world-wide sea waters, coastal regions, streams and lakes of North America, Europe, West Africa, Australia, Chile, Japan, New Zealand, Tasmania.
HABIT AND HABITAT
- Petromyzon is found both in salt and fresh-water. They lead an ectoparasitic life on other fishes, attaching to the body of host by buccal funnel and secreting an anticoagulant for continuous flow of blood. They are also anadromous i.e., ascending river for spawning. Carnivorous and predators.
GENERAL CHARACTERSTICS OF PETROMYZON OR LAMPREY
- Commonly called as lamprey.
- Body is eel-like, measuring about 90 cm, and differentiated into head, trunk and tail. First dorsal fin, second dorsal fin and caudal fin confluent.
- Skin is without scales, slimy, green, brown and with strong metallic lusture.
- Head contains mouth but no jaws. Mouth is surrounded by a large, ventral, suctorial funnel with numerous horny teeth. The ‘tongue’ is toothed and piston-like.
- Dorsal nasal sac and mouth are unconnected. Paired eyes are present behind nasal-aperture.
- Gill-slits are 7 pairs and branchial basket is well developed.
- Sexes are separate. Female with large anal fin. Male with urinogenital or copulatory papilla. The development includes ammocoete larva which is very important phylogenetic ally as it is regarded a connecting link between Amphioxus and cyclostomes.
- Lampreys have very little food value.
- They injure and destroy fishes by sucking blood and causing secondary infection.
- Larval lampreys are used as bait for sport fishing and commercial fishing.
Lampreys are the lowest jawless vertebrates and their nearest allies are the ancient ostracoderms of Silurian and Devonian periods. There are no fossil representatives of this group to indicate their course of evolution.
The animal has 7 pairs of gill pores and is without jaws and has above features, hence it is Petromyzon.