Class — Cyclostomata general features

• Class — Cyclostomes

• All living members of the class Cyclostomata are ectoparasites on some fishes like shark..

•  Cyclostomes   have an elongated body bearing 6-15 pairs of gill slits for respiration.

• They  have a sucking and circular mouth without jaws.

•  Cyclostomata body is devoid of scales and paired fins.

• They have Cranium and vertebral column with cartilage.

• Circulatory system is of closed type.

• Cyclostomes are marine organisms but can  migrate for spawning to fresh water.

• After spawning, within a few days, they die and their larvae, after metamorphosis,

• return to the ocean.

• Eg

• Petromyzon (Lamprey)

• Myxine (Hagfish).