Phylum Rotifera

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