1. Presentation on Petromyzon marinus Dr. Jagdish Kaur P.G.C., Sector 11
CHANDIGARH

2. CLASSIFICATION: PHYLUM : CHORDATA SUB PHYLUM : VERTEBRATA
CLASS : CYCLOSTOMATA
ORDER : PETROMYZONTIA
FAMILY: PETROMYZONTIDAE
GENUS : PETROMYZON
SPECIES : marinus

3. Most primitive living vertebrate.
Called ostracoderms (extinct palaeozoic fish like jawless vertebrate characterised by heavily armoured body.)
About at present 30 species, both fresh water and marine water.
Some of them are- Petromyzon marinus ,Lampetra fluviatilis,Lampetra planeri
Petromyzon marinus is the best known species.

4. External characters of petromyzon
Marine animal and keeps near the bottom.
Sanguivorous (blood sucking) ectoparasite.
Water is drawn into gill pouches and expelled out through external gill slits for respiration.
Actively swims about in water by lateral undulations of its highly muscular body.
Breeds only once in its whole life.

5. Fertilization is external.
Life history includes a larva called ammocoetes
Lamprey have no bones.
they do not occur in fossil record.
It destroys valuable food fishes by sucking their blood.
Body is long, slender, eel like and scale less
Body is somewhat greenish with patches of dark color on the back.
Underside is pale or white.
Body is about 90cm long.

6. lamprey

7. BODY REGIONS 1.Head : a) mouth b) naris c) eyes d) gill slits 2. Trunk
Mainly divided in three parts:
1.Head :
a) mouth
b) naris
c) eyes
d) gill slits
2. Trunk
3. Tail

8. MOUTH OF LAMPREY

9. Naris: Lies on the dorsal surface of the head.
Leads into blind sac olfactory sac ,which serves as organ of smell.
Behind the naris is the pineal eye present.
Eye:
Occupy lateral position in theLack headeyelids and covered by transparent skin, conjuctiva. .
Gill slits:
Are small,rounded apertures present in two longitudinal rows behind eyes one on either side
Water enters and leaves alternately for respiration.

10. Trunk:
Lacks paired appendages. Bears anterior and posterior dorsal fins supported by fin rays.
At junction with tail,cloaca is present with a very small aperture anus.
Behind the anus lies the urinogenital aperture.
Tail:
. bears the caudal or tail fin. Tail fin supported by fin rays.

11. BODY WALL SKIN: skin, muscles and peritonium . Epidermis and dermis.
composed of many layers of cells.
Mucus glands are present in the epidermis.
. Dermis
thinner than the epidermis.
Formed of collagen and elastin fibres vessels,nerves and smooth muscle fibres.
Beneath the dermis is the subcutaneous tissue containing fat.

12. MUSCLES:
Muscles of trunk and tail are arranged in zigzag segments, the myomeres separated by connective tissue septa called mycommata.
Contraction of myomeres on one side causes bending of the entire body in that direction so locomotion is brought by alternate contraction of right and left myomeres.

13. COELOM: Body wall encloses a cavity called coelom in the trunk.
Divided into two parts: a) pericardial cavity containing pharynx and heart.
b) abdominal cavity containing digestive and urinogenital organs except kidneys.
. Lined by parietal peritonium.
Pericardial cavity communicates with the abdominal cavity in larva by pericardio-peritoneal pore.

14. ENDOSKELETON:
. Is cartilagenous in petromyzon. . Comprises of skull and notochord. SKULL: . Is simple and primitive. Floor of cranium is formed of basal plate. . At middle is the prominent aperture,basicranial-fontanelle,for the passage of duct of naso-hypophysial sac. . At sides of basal plate auditory capsule are present. A median olfactory capsule is attached to cranium by fibrous tissue only.

15. Structure of skull

16. VERTEBRAL COLUMN: Persists throughout the life.
Enclosed by chordal sheath.
Supports the spinal cord and the brain.
From the sides of notochord arise the small,vertical cartilages that extend upward on the sides of spinal chord.
These cartilages correspond to neural and interneural arches and similar cartilages in the tail region extend downward as haemal arches.

18. 1. Primitive characters A single median naris. Lack of scales.
Differences from fishes
Resemblances with cephalochordates
A single median naris.
Lack of scales.
Lack of jaws,ribs and girdles.
Lack of stomach.
Lack of spleen.
Lack of gonoducts.
Absence of true teeth.
Unconstricted notochord.
Incomplete cranium and vertebrae
Poorly developed spiral valve
Lack of exoskeleton.
Lack of paired fins.
Straight alimentary canal.
Numerous gill slits.
Indistinct head.
Absence of gonoducts.
External fertilization.
Extension of myotomes from head to tail.
Persistent unconstricted notochord.
Separate dorsal and ventral roots of spinal nerves.

19. 2. Vertebrate characters:
Head with paired sense organs.
Several layered epidermis.
Cranium for the protection of brain.
Gills for respiration.
Segmented vertebral column.
Leucocytes and erythrocytes in the blood.
Sympathetic nervous system.
Lateral line sense organs.
Complicated kidneys.
Lymphatic vessels.

20. 3. Special characters:
Buccal funnel with a horny teeth for attachment.
Sucking mouth.
A single median naris
Numerous slime glands.
Pharynx having branchial basket.
Peculiar sac like gill chambers.
A large thyroid gland.
Presence of naso-hypophysial sac.

22. Free living species metamorph into adults and immediately
Lamprey life cycle
Eggs hatch in
12-14 days
Ammocoete stage
Free living species metamorph into adults and immediately
return to spawning site to mate and then die

23. THANKS A LOT………………