1 / 15

Platyhelminthes

Platyhelminthes. Acoelomate Flatworms. Today’s Objective. TSW take notes on the phylum Platyhelminthes including economic importance, an overview of class characteristics, and ecological niches. General Flatworm Characteristics. Acoelomate – no body cavity coelom- solid mesenchyme (mesoderm)

trista
Download Presentation

Platyhelminthes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Platyhelminthes Acoelomate Flatworms

  2. Today’s Objective • TSW take notes on the phylum Platyhelminthes including economic importance, an overview of class characteristics, and ecological niches.

  3. General Flatworm Characteristics • Acoelomate – no body cavity coelom- solid mesenchyme (mesoderm) • First phylum to show a definite cellular mesoderm • Bilaterally symmetrical • Triploblastic; 3 distinct tissue or germ layers • Dorsoventrally flattened

  4. General Characteristics (cont.) • Respiration by diffusion • Digestive system extensively branched • One opening for feeding and waste removal • Lack an anus • Primitive kidneys – protonephridia with “FLAME CELLS”

  5. General Charcterisitcs (cont.) • First evidence of cephalization primitive brain • Some have eyespots • Directional movement • No true respiratory system or circulatory system • Usually hermaphroditic

  6. Class Turbellaria • Free-living flatworms • Some freshwater (Planaria), marine, or terrestrial • Most move by circular and longitudinal muscles • Some move by using cilia (or cilia + mucus)

  7. Turbellarian Feeding - Carnivorous • Wrap body around prey • Entangling with mucous • Ingest the whole prey or suck its juices through a hardened stylet (modified pharynx) • in many species the pharynx is completely eversible and can envelope the entire prey • there is no anus so ingestion and egestion are through the mouth

  8. Turbellarian Reproduction • Sexual Reproduction • Most hermaphroditic • Both sex organs discharge gametes into a common chamber even though this is true- cross fertilization is the most common mode of reproduction • Some self fertilization can and does occur • Asexual Reproduction • Fragmentation and Regeneration

  9. Dugesia

  10. Class Monogenea • Parasitic • Flukes • Only one host • Most external parasites • Gyrodactylus • Polystoma • Can cause major economic losses to fisheries

  11. Class Trematoda • Digenetic Flukes • Complex life history, involves 2 or more hosts • Live in every type of environment • 5,000+ known species • Live mostly in digestive system or associated organs (all parasitic)

  12. Some Trematodes of Importance • Clonorchis – Chinese human liver fluke • Fasciola hepatica – Liver fluke • Schistosoma – Blood fluke • Know this life cycle! • Where they are present it is hazardous to bathe, drink, wade in or dip your arms in infested waters!

  13. Class Cestoda - Tapeworms • Long, Flattened • White or Yellow in color • All parasitic! • Adults almost always live in the intestines of their hosts • Body has protective cuticle • Head (scolex) has multiple disks of hooks for attachment

  14. Cestodes (cont.) • Can reach up to 50 ft. in length! • No specialized sense organs • Reproduce using proglottids (segments) • Contain flame cells, nerves, muscles, male and female reproductive organs • Shed in feces of host • Taenia saginata – beef tapeworm • Taenia solium – pork tapeworm

  15. Tapeworm Structure

More Related