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Phylum Rotifera

Phylum Rotifera. > 1,800 described species < 1 mm Complex, variety of body forms Solitary Pseudocoelomate Generally freshwater. Rotifer body. Head, trunk, foot Ciliary organ on anterior end = corona Complete gut Protonephridia Tendency to constant cell number

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Phylum Rotifera

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  1. Phylum Rotifera • > 1,800 described species • < 1 mm • Complex, variety of body forms • Solitary • Pseudocoelomate • Generally freshwater

  2. Rotifer body • Head, trunk, foot • Ciliary organ on anterior end = corona • Complete gut • Protonephridia • Tendency to constant cell number • Pharynx modified with internal jaws

  3. Posterior • Elongate foot • Cuticular annuli with telescoping action • “toes” for attachment

  4. Locomotion • Some can change shape by “telescoping” action • Some sessile as adults • Hydrostatic skeleton • Most rotifers swim and crawl • Cilia

  5. Digestion • Complete digestive tract Mouth --> buccal tube -->Pharynx (mastax) -->Salivary gland -->Gastric gland -->Stomach -->Intestine -->Nephridioduct -->Cloaca -->Anus

  6. Circulation, Gas Exchange • No special organs for internal transport or gas exchange • Coelomic fluid • aided by muscles • small size reduces diffusion and transport tissues

  7. Osmoregulation • one pair of flame bulbs protonephridia • empties into cloaca

  8. Nervous System and Sense Organs • Bilobed mass of gangli • Nerves connect to body • Chemoreceptors, mechanoreceptors

  9. Reproduction • Parthenogenesis • Development from egg w/o fertilization • = most rotifers female • Adaptation for freshwater habitats with severe disturbance • If males exist -- copulation • or hypodermic impregnation

  10. Phylum Acanthocephala • Spiny – head worms • 1200 species • All gut parasites of vertebrates

  11. Phylum Acanthocephala • Life cycle requires intermediate host – usually arthropod • Fig. 10.18 Pechenik

  12. Cyst out w/feces • Snail eaten by turtle Adult worm in turtle intestine • Cyst eaten by ostracod • Ostracod eaten by snail

  13. Phylum Acanthocephala • Constant number of cells • No respiration organs • No digestive organs • Pseudocoelom

  14. Phylum Acanthocephala • Proboscis for attachment to intestinal wall • Dioecious • Fertilized eggs develop in pseudocoelom of female • To acanthor stage

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