Myxine (Hagfish)





Petromyzon (Lamprey)
I Hag fishes are scavengers. They penetrate into the dead fishes bodies and eat the tissues. 1.They are semi parasitic. But the Larvae(Ammocoetes) leads an independent life.
2. The body is. slender & eel-like 2. The body is cylindrical & stout.
‘3 They are exclusively marine habitats.

3. These live in both in sea water and fresh water. They migrate into the rivers for spawning.


4. the caudal fin is small.

4. The caudal fin is well developed.



5. The dorsal fin is not fully developed. 5. The dorsal fin is divided into two portions by a notch.
6. Mouth is terminal in position. It is surrounded by soft lips. Buccal funnel is absent. 6. Mouth is sub-terminal in position. Buccal funnel is present.
7. Single nostril is present very near to the mouth. 7. Single nostril Is on the dorsal side of head region.
8. Skull has no roof. 8. Skull roc is incomplete.
9. Small teeth are present on the tongue in two rows. 9. Horny teeth are present in the buccal funnel and on the tongue.
10. Salivary glands are present. 10. Paired salivary glands are present
11. The gill pouch number varies from six to fifteen pairs. 11. There are seven pairs gill- pouches present. All these open Into the respiratory tube.
12.Each aortic ‘arch supplies the hemibranch of a single gill pouch. 12. Each aortic arch divides and the branches enter the posterior hemibranch of the nearby gill pouch.
13. Brain is degenerated. 13. Brain is well developed.
14. Only thee pairs of cranial nerves are present. 14. Ten pairs of cranial nerves are present
15. Non functional paired eyes are burned in the skin. 15. Paired functional eyes are present.
‘16. Penial eye is absent. 16. Penial eye is present.
17. In the adult pronephros is retamed. But the functional kidney Is of mesonephric type and simple. 17. The functional adult kidney is mesonephric type.
18. UrinogenitaL sinus is not seen: 18. Urinogenital sinus is formed.
19. Sexes are united - Hermaphrodite. The anterior part of the gonad acts as ovary & the posterior part act Like Testis.



20. The eggs are large and covered by cylindrical horny shell, 20. The eggs are small and are not covered by horny shell.
21. The development is direct 21 Development is indirect. Arnmocoetes larva occurs in the life-history.




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