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PLATYHELMINTHES

Commissionerate of Collegiate Education. PLATYHELMINTHES. GENERAL CHARACTERS. Commissionerate of Collegiate Education. REPRESENTATIVES. Commissionerate of Collegiate Education. REPRESENTATIVES. Commissionerate of Collegiate Education. REPRESENTATIVES.

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PLATYHELMINTHES

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  1. Commissionerate of Collegiate Education PLATYHELMINTHES GENERAL CHARACTERS

  2. Commissionerate of Collegiate Education REPRESENTATIVES

  3. Commissionerate of Collegiate Education REPRESENTATIVES

  4. Commissionerate of Collegiate Education REPRESENTATIVES

  5. Commissionerate of Collegiate Education ORIGIN The term ‘Platyhelminthes’ was coined by Geganbaur

  6. Commissionerate of Collegiate Education PROFILE OF THE PHYLUM • About 20,000 species • About 80% of parasites are from this phylum

  7. Commissionerate of Collegiate Education CHARACTERS • Free-living or parasitic • Bilaterally symmetrical, and • Dorso ventrally flattened • First animals with 3 germ layers - triploblastic • Ectodermis • Mesodermis • Endodermis • Epidermis has cilia or cuticle • Coelom lacking (acoelomate)

  8. Commissionerate of Collegiate Education CHARACTERS Exhibits bilateral symmetry: anterior and posterior ends are different; so are the dorsal (top) and ventral (bottom) surfaces

  9. Commissionerate of Collegiate Education CHARACTERS Exhibit some degree of cephalization Commonly referred to as the 'flatworms' because their bodies are dorsoventrally flattened.

  10. Commissionerate of Collegiate Education ORGAN SYSTEMS • Digestive system incomplete • Excretory system – protonephridia • Nervous system – ladder-like • Respiratory, circulatory, and skeletal system lacking • Most monecious • Some have fragmentation and regeneration (Asexual)

  11. Commissionerate of Collegiate Education DIGESTIVE SYSTEM • Some of the flatworms possess a digestive system, with a mouth, pharynx, and a branching intestine from which the nutrients are absorbed • The intestine, with only one opening, is a blind system

  12. Commissionerate of Collegiate Education EXCRETORY SYSTEM (OSMOREGULATION) • A network of water collecting tubules adjacent to flame cells or a protonephridia • When cilia beat they move water into the tubules and out the body through pores called nephridiopores

  13. Commissionerate of Collegiate Education EXCRETORY SYSTEM (OSMOREGULATION)

  14. Commissionerate of Collegiate Education MUSCULAR SYSTEM • Below the epidermis are layers of circular and longitudinal muscle fibers; used in locomotion

  15. Commissionerate of Collegiate Education NERVOUS SYSTEM • Includes: anterior cerebral ganglia, longitudinal nerve cords, and some lateral nerves • Most free living planarians and parasitic larval forms possess a variety of sensory organs (e.g., eye spots, statocysts, rheoreceptors)

  16. Commissionerate of Collegiate Education NERVOUS SYSTEM • Includes: anterior cerebral ganglia, longitudinal nerve cords, and some lateral nerves • Most free living planarians and parasitic larval forms possess a variety of sensory organs • (i.e., eye spots, statocysts, rheoreceptors)

  17. Commissionerate of Collegiate Education REPRODUCTIVE SYSTEM • Most are capable of some form of asexual reproduction (e.g., many turbellarians reproduce by fission) • Most flatworms are hermaphroditic; but exchange gametes takes place between different individuals

  18. Commissionerate of Collegiate Education REPRODUCTIVE SYSTEM • Fertilization is internal • Fertilized eggs are shed in protective capsules • Development includes larvae

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