The upcoming discussion will update you about the difference between Myxine and Petromyzon.
Difference # Myxine (Fig.5, 6):
1. Myxine is exclusively marine.
2. The fin of Myxine is confined to tail.
3. Numerous large glands are present in the complex slimy skin of Myxine.
4. Buccal funnel is absent in Myxine. The mouth is edged with tentacles supported by cartilage.
5. A single median tooth and two rows of smaller teeth present on the tongue.
6. Eyes of Myxine are hidden and rudimentary.
7. Six pairs of gill pouches opening directly into the gullet and less directly to the exterior.
8. Ear with an utriculus and two semicircular canals.
9. The nostril large, unpaired, dorsal and opens into the pharynx through a passage, the pituitary sac.
10. A velum separates the buccal cavity from the pharynx.
11. The intestine of Myxine is very wide and bears longitudinal ridges.
12. No urinogenital sinus, only one genital pore.
13. Skull of Myxine is without any roof.
14. Skeletal system of Myxine is less developed, only a hint of a branchial basket.
15. Cerebrum and cerebellum rudimentary.
16. Protandrous hermaphrodite.
17. Ova of Myxine is large and oval with attaching threads.
18. Cleavage meroblastic in Bdellostoma.
19. Development direct in Bdellostoma.
Difference # Petromyzon (Fig.7):
1. Petromyzon live in rivers and seas.
2. Petromyzon have two unpaired dorsal fins and a tail fin.
3. Sensory structures in the complex, slimy, pigmented skin.
4. Buccal funnel is present in Petromyzon, surrounded with papillae.
5. Teeth many, yellow and horny. The tongue also bears horny teeth.
6. Eyes are hidden and retarded in the larva, exposed and complete in the adult Petromyzon.
7. Seven pairs of gill pouches, opening directly to the exterior and less directly into the adult gullet.
8. Ear of Petromyzon is more complex and has a sacculus in addition.
9. The nostril unpaired, dorsal and ends blindly in the pituitary sac.
10. A velum guards the respiratory tube from the buccal cavity.
11. The intestine is without convolution. Typlosole and slight spiral valves present.
12. A urinogenital sinus and two genital pores.
13. Skull of Petromyzon is very imperfectly roofed.
14. Hints of vertebral arches, cartilaginous branchial basket round gill pouches.
15. All the components of the brain are distinct and well-marked.
16. Sexes are separate in Petromyzon.
17. Ova of Petromyzon is small and spherical, threads.
18. Cleavage holobastic.
19. Development with a metamorphosis.