activity 2 - amphioxus
Download as PPT, PDF17 likes11,484 views
1) Amphioxus is a small, semitransparent marine animal that lacks distinct head and has a notochord extending to its head. 2) It has gill slits for filtering food particles from water and an endostyle for processing food in its pharynx. 3) Amphioxus spends much of its time buried in ocean sediment and uses rapid body movements and its notochord extending to its tip to burrow, and contracts its myomeres muscles to swim.
activity 2 - amphioxus
- 1. amphioxus
- 2. introduction Organisms under Subphylum Cephalochordata: • Has no distinct head • But has a notochord that extends to the head part of the body.
- 3. introduction: Amphioxus: - means “sharp at both ends” - a living amphioxus is semitransparent but becomes opaque when immersed in preserving fluids.
- 4. Amphioxus and the Vertebrates
- 5. No cephalization No paired sense organs
- 6. Has notochord that remains throughout life Has no vertebral column Notochord
- 7. Has pharyngeal slits but in large numbers
- 8. Dorsal, hollow nervous system No brain or cranium
- 9. Metameric muscles (myomeres) but extendes to the anterior tip of the head
- 10. Two-layered skin – epidermis and dermis But outer layer is one-cell thick
- 11. Well-developed circulatory system Lack blood cells, muscular heart Pulsating blood vessels
- 12. Is coelomate But gretly restricted
- 13. External morphology of amphioxus
- 14. MYOMERE S •Lie immediately under the thin skin throughout the entire length of the body •Provide locomotion MYOSEPT A a connective • tissue partition to which longitudinal muscle bundles attach •It separates the myomeres
- 15. GONAD S •Visible through the body wall and bulge into the water- filled atrium, into which sperm or eggs are shed ATRIOPORE •It is where the excess water , gametes and metabolic wastes exits
- 16. BUCCAL CIRRI •Partially strain the water as it enters the vestibule and monitor it chemically
- 17. Dorsal and ventral fin rays: maintains balance during locomotion
- 18. GILL SLITS EYESPOT OCELLI GILL BARS WHEEL ORGAN
- 19. GILL SLITS : where water goes through; where strings of mucus travelling across them trap tiny food particles GILL BARS : supports between gill slits OCELLI : light-sensitive organ; it assist in orienting the animal as it burrows in the sand
- 20. WHEEL ORGAN : retrieves some of the heavier food particle that miss the mouth, and it directs these through the mouth and into the pharynx along with the water stream
- 21. Internal Structure of Amphioxus
- 24. Parts and Function Notochord: protects and support the dorsal nerve cord; serves as the major skeletal support throughout life Nerve cord: serves as central nervous system. Pharynx: passage way for water, food and air. Atrium: serves as a collecting chamber for respiratory water that has passed over the gills.
- 25. Intestine: major site for digestion of food. Anus: excretion of waste
- 26. Anterior end
- 27. Vestibule: collecting chamber for sea water Oral hood: serves as entrance and storage Velum: works as valve and filter; surrounds the mouth Velar tentacles: prevent undesirable objects from entering the digestive cavity
- 29. Amphioxus spend much of their time buried in gravel or mud on the ocean bottom
- 30. When feeding, they let the anterior part of the body project from the surface of the gravel so that they can filter food particles from water passing through their gill slits.
- 31. FEEDING:
- 32. Feeding: Once the food is in the pharynx it is processed as follows. Epibranchial groove Hypobranchial groove or endostyle
- 36. They burrow into sand using rapid movements of the body The continuity of the notochord to the very tip of the rostrum may be an adaptation for burrowing in sand.
- 37. The animals swim by contracting the muscle blocks, or myomeres, that run from end to end on each side of the body.
- 38. The blocks on each side are staggered, producing a side-to-side movement of the body when swimming.