Ecdysozoa-Nematoda

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Author:
schoenbe
ID:
268530
Filename:
Ecdysozoa-Nematoda
Updated:
2014-03-30 20:12:16
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  1. Ecdysozoa
    molt: shed entire cuticle (non-living outer layer), new cuticle is grown under old one
  2. Cuticle
    • epidermis is below cuticle
    • frequently sclerotized (hardened)
  3. Epidermis
    • below cuticle¬†
    • living cells that secrete substances to the cuticle
  4. 3 layers of the cuticle?
    • endocuticle (bottom layer)
    • exocuticle
    • epicuticle (top layer)
  5. sclerites
    hardened body parts shaped like plates
  6. Molting steps (10)
    • 1. epidermis separates from endocuticle
    • 2. inactive molting fluid released by epidermis
    • 3. thin protective layer deposited over epidermis, under molting fluid
    • 4. enzymes in moulting fluid digest endocuticle, absorbed by epidermis
    • 5. undifferentiated cuticle deposited under protective layer
    • 6. moulting fluid reabsorbed
    • 7. epicuticle laid down
    • 8. old exo and epi cuticle shed through ecdysis
    • 9. new cuticle expanded by swallowing air
    • 10. new cuticle hardened
  7. Phylum Tardigrada "water bears"
    • mostly freshwater, moss and soil
    • no anntenae
    • whole body acts as gill
    • withstand desication
  8. Phylum Nematoda (roundworms and threadworms)
    • no segmentation, appendages, or eyes
    • moult
    • pseudocoelomate
    • internal fertilization, some hermaphrodites
    • direct development
    • Eutelic
  9. Cause of Nematoda's simplicity?
    secondary simplification from complex body design
  10. Pseudocoelomate
    have a body cavity but it is not completely lined by mesoderm
  11. Eutelic
    Post embryonic growth is done through existing cell growth, not by addition of new cells
  12. Nematode Ecology
    • Habitat/role: aquatic, predators, microbivores, decomposition, nutrient cycling
    • Many parasitic

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