General Characters and Comparison of Cyclostomata: Petromyzon vs. Myxine
Cyclostomata, a group of jawless vertebrates, comprises hagfishes and lampreys, exhibiting unique characteristics such as cylindrical body, lack of pair fins, smooth skin, and presence of mucous glands. They possess specific features like circular mouth with teeth, lateral line sense organ, and two-chambered heart. The comparison between Petromyzon (Lamprey) and Myxine (Hagfish) highlights distinctions in habitat preference, body structure, fin development, nostril position, gill slits arrangement, and feeding mechanisms. These differences showcase the diversity within the Cyclostomata class.
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General Characters of Cyclostomata and Comparison between petromyzon and myxine
Cyclostometa - Cyclos means circular, stoma-mouth. Extant group of Jawless vertebrates. Includes Hag fishes, Lampreys. lamprey-hagfish
General Characters of Cyclostomes About 50 species are recognised ,living in the marine water but lampreys migrate into fresh water for breeding. Body is cylindrical, elongated and eel like. Pair fins are absent(Pectoral and pelvic fins),but dorsal fin and caudal fins are present. Skin is smooth, slimy and without scales, contains numerous unicellular mucous glands. Mouth-circular-base of buccal funnel- acts as a sucker for attachment(lampreys),but in tentacles. Presence of Single external nostril-also called monorhina. Presence of a pair of eyes - on lateral sides of a head. hag fishes, mouth-surrounded .
General Characters of Cyclostomes Tongue has teeth - acts as a rasping organ. Presence of lateral line sense organ. Internal ear has 1 or 2 semi circular canals. True coelom is seen. Endoskeleton cartilagenous Z shaped myotomes present in trunk as well as tail, buccal funnel has radial muscle, tongue has protractor and retractor muscle. Alimentary canal is straight. Presence of 5-16 pairs of gill pouches open out through 1-16 pairs of gill slits. Presence of two chambered of heart
General Characters of Cyclostomes Notochord persists throughout the life. Neural arches of vertebrae are incompletely formed 8-10 pairs of non myelented cranial nerves. Presence of Mesonephric and pronephyric kidneys. Unisexual and bisexual. Gonad without a gonoduct External fertilization. Indirect and direct development and see the ammocoetes larva. Examples:-Petromyzon, Ichthyomyzon, Lampetra, Entospherus, Myxine, Paramyxine.
Comparison of petromyzon and Myxine Petromyzon Myxine 1.Live in marine water but migrates to fresh water for breeding (Anadromous migration) . exclusively marine habitats. 2. Commonly known as Lamprey. commonly Known as Hag fish. 3. Body is elongated and cylindrical. elongated and eel like. 4. Dorsal fin is well developed, divided into two portions by a notch. not developed. 5.Single nostril (monorhina) is on the dorsal side of head region. very near to the mouth. 6.Anteroventrally, head posses a buccal funnel. It acts as a sucker for attachment to host. Mouth is terminal position, surrounded by tentacles. Buccal funnel is absent. 7. Buccal funnel and tongue have horny teeth. Teeth are present on tongue only. 8. Seven pairs of gill slits are present. Six pairs of gill pouches open out through a single pair of gill slit.
Comparison of petromyzon and Myxine Petromyzon Myxine 8. Presence of pineal eye. Absence of pineal eye. 9. Presence of ten pairs of cranial nerves Presence of eight Pairs of cranial nerves. 10. Internal ear with two semi circular canals. a single semi circular. 11.Presence of mesonephric kidneys presence of pronephric. 12. It is Unisexual bisexual 13.The eggs are small and are not covered by horny shell. are large and covered by cylindrical horny shell. 14. Indirect development, seen a free swimming larva is ammocoetes. direct development 15. Adult stage leads ectoparasitic on fishes. Feeds on dead fishes and decomposing organic matter.
