Phylum Rotifera

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Phylum Rotifera

  1. 1. PHYLUM ROTIFERA Philodina
  2. 2. PHYLUM ROTIFERA <ul><li>Rotifera- Latin word meaning “wheel-bearer” ( rota =wheel + fero =to bear). </li></ul><ul><ul><li>composed of several ciliated tufts around the mouth that in motion resemble a wheel </li></ul></ul>Structure of Philodina ; a live Philodina
  3. 3. <ul><li>2000 species throughout the world. </li></ul><ul><li>- freshwater inhabitants </li></ul><ul><li>- marine </li></ul><ul><li>- terrestrial </li></ul><ul><li>- epizoic or parasitic </li></ul><ul><li>- benthic – swim or creep on vegetation </li></ul><ul><li>Range in size – 40 µ m- 3mm in length. </li></ul><ul><ul><ul><ul><ul><li>- most are between 100-500 µm long. </li></ul></ul></ul></ul></ul><ul><li>Some have beautiful colors, most are transparent. </li></ul>PHYLUM ROTIFERA
  4. 4. <ul><li>The morphology is very diverse, but their body is cylindrical or spherical. </li></ul><ul><ul><li>Floaters - globular & saclike </li></ul></ul><ul><ul><li>Creepers & swimmers – elongated and wormlike </li></ul></ul><ul><ul><li>Sessile - vaselike </li></ul></ul>PHYLUM ROTIFERA
  5. 5. PHYLUM ROTIFERA Variety of form in rotifers
  6. 6. PHYLUM ROTIFERA <ul><li>Morphology of rotifers: </li></ul><ul><ul><li>Head : bears  a ciliated crown or corona , </li></ul></ul><ul><ul><ul><ul><li>locomotion and feeding . </li></ul></ul></ul></ul><ul><ul><ul><ul><li>The cilia create currents of water toward the mouth- draw in small planktonic food. </li></ul></ul></ul></ul><ul><ul><li>Trunk : contains visceral organs. </li></ul></ul><ul><ul><li>Foot : segmented (when present). </li></ul></ul><ul><ul><ul><ul><li>Ringed with joints that can telescope to shorten (in some sp.). </li></ul></ul></ul></ul><ul><ul><ul><ul><li>The 1-4 toes secrete a sticky substance from the pedal glands for attachment. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Used by both sessile and creeping forms. </li></ul></ul></ul></ul>
  7. 8. <ul><li>Digestive system- complete </li></ul><ul><li>Omnivorous: feed by sweeping minute organic particles / algae forward the mouth by the beating of the coronal cilia. </li></ul><ul><li>Carnivorous (some sp.)- feed on protozoa & small metazoans- capture by trapping or grasping. </li></ul><ul><ul><li>Trappers - funnel-shape area around the mouth to capture prey. </li></ul></ul><ul><ul><li>Hunters - trophi that can be projected & used like forceps to seize prey. </li></ul></ul>PHYLUM ROTIFERA
  8. 9. <ul><li>Pharynx ( mastax ) fitted with a muscular portion that is equipped with hard jaws ( trophi )- sucking & grinding up food particles. </li></ul><ul><li>Absorption occurs in the stomach. </li></ul>PHYLUM ROTIFERA
  9. 12. <ul><li>Reproduction: </li></ul><ul><li>Female rotifers (have 1 or 2 syncytial ovaries (germovitellaria) . </li></ul><ul><ul><li>Produce yolk as well as oocytes. </li></ul></ul><ul><li>Rotifers are dioecous, but males are unknown in many species. </li></ul><ul><ul><li>(Dioecous- having male & female organs in separate individuals). </li></ul></ul>PHYLUM ROTIFERA
  10. 13. <ul><li>Divided into 3 classes: </li></ul>PHYLUM ROTIFERA class order
  11. 14. <ul><li>Class Seisonidea (most primitive) : </li></ul><ul><ul><li>Marine </li></ul></ul><ul><ul><li>Elongate form </li></ul></ul><ul><ul><li>Corona vestigial </li></ul></ul><ul><ul><li>♀ & ♂ similar in size and form </li></ul></ul><ul><ul><li>Single genus: Seison </li></ul></ul><ul><ul><li>Epizoic on gills of a crustacean </li></ul></ul><ul><ul><li>Seisonidea : females produce haploid eggs that must be fertilized and develop into either males or females. </li></ul></ul>PHYLUM ROTIFERA Crustacea: Nebalia Seison annulatus
  12. 15. <ul><li>Class Bdelloidea: </li></ul><ul><ul><li>Swimming or creeping forms </li></ul></ul><ul><ul><li>Anterior end rectractile </li></ul></ul><ul><ul><li>Corona usually with pair of trochal discs </li></ul></ul><ul><ul><li>Males unknown </li></ul></ul><ul><ul><li>2 germovitellaria </li></ul></ul>PHYLUM ROTIFERA
  13. 16. <ul><ul><li>Bdelloidea : females are parthenogenetic (asexual)- produce diploid eggs that hatch into diploid females. </li></ul></ul><ul><li>Examples: Philodina & Rotaria </li></ul>PHYLUM ROTIFERA Philodina Rotaria
  14. 17. <ul><li>Class Monogononta: </li></ul><ul><ul><li>Swimming or sessile forms </li></ul></ul><ul><ul><li>Single germovitellarium </li></ul></ul><ul><ul><li>Males reduced in size </li></ul></ul><ul><ul><li>Examples: Asplanchna & Epiphanes </li></ul></ul>PHYLUM ROTIFERA Asplanchna Epiphanes
  15. 18. PHYLUM ROTIFERA <ul><li>Monogononta : females produce two kinds of eggs; </li></ul><ul><ul><li>Amictic eggs- diploid eggs that have not undergone reduction division, cannot be fertilized & develop only into females. </li></ul></ul><ul><ul><li>Mictic eggs- undergone meiosis and are haploid- if: </li></ul></ul><ul><ul><ul><li>Unfertilized- develop quickly into males. </li></ul></ul></ul><ul><ul><ul><li>Fertilized- they secrete a thick shell and become dormant for several months before developing into females. </li></ul></ul></ul>
  16. 19. <ul><li>The importance of rotifers in the ecosystems??? </li></ul>PHYLUM ROTIFERA

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