Class cyclostomata Lamprey and Hag fishes.class-11-Biology.

    SUB PHYLUM VERTEBRATA

        CLASS-CYCLOSTOMATA

The general characteristics of these class are:

1. The members of this class  consist of circular sucking mouth without jaw, scale.  
2. They have fish like vertebrates in which teeth disperse through out the mouth. 
3. All living members of this class are ectoparasite on aquatic animals. 
4. They have 7 to 14 pair of gills slits for respiration. 
5. The body is  elongated like an eel but paired fins are absent. 
6. The digestive system have no stomach and have single nostril (monorhina).
7. The heart is two-cambered The lateral line acts as a sense organ.
8. They have  ten pairs of cranial nerves .
9. The sexes are separate. 
10. Example:--Hag fishes (Myxine)--Lamprey-(Petromyzon).

Respiration.

The member of this  class  breath via 7-to 14 pair of gills, water with dissolve oxygen inter into mouth gills have  a network of blood capillaries take oxygen from water and add carbon dioxide into water .
The oxygenated blood transport to whole bodies for cellular respiration.

Digestion:

They have no stomach and intestine because they are ectoparasites, they suck blood having digested food.
They have no stomach and intestine because no need to digest food.

Circulation:

They have two chamber heart (auricle and ventricle) along with sinus Venuses and cones arteriosus .The deoxygenated blood inter from whole body into sinus Venuses from there it inter into atrium, then inter into ventricle ,ventricle pump it strongly to gills and whole body from conus arteriosus. This type of circulation is called single circuit circulation.

                                           The path of circulation:

Reproduction:

The member of this class live in marine but migrate to fresh water for spawning egg and release sperm  (Anadromous migration).

They lay egg and release sperm at same time by closing their cloaca in their nest of fresh water and die the egg and sperm fertilize in fresh water to form zygote (external fertilization).

After some days zygote develop into larva called  ammocoetes larva or larva of lamprey. Hag fish have no larva. Hag fish have slime gland that secrete slime to defence. Human use these slime for making fibre and other things.