Zoo3 3rd Lect Exam

Ecdysozoans
_ One of the two large subdivisions within the Protostomia
_ Builds a cuticle, an outer layer of organic material that functions as its skeleton _ Cuticle is regularly shed (ecdysis)
_ Have separate sexes and copulate

Ecdysozoa Cuticle – nematode and arthropod

Phylum Nematoda (15,000 species)
(Gr. nematos, thread)
_ marine, freshwater, terrestial or parasitic
_ long cylindrical body
_ cuticle (cortical, matrix and fibrous)
_ hydrostatic skeleton
_ longitudinal muscles only
_ pseudocoelom (false body cavity)
_ complete digestive system
_ sexes separate (exhibits sexual dimorphism)
_ excretory system - gland cells (renette gland)
_ nervous system
– nerve ring with ganglia
– sense organs
• papillae - labial, cephalic
• setae - sensory, mechanoreceptors
• amphid - anterior chemoreceptor
• phasmid –posterior glandulosensory structure

Classification

1. Class Phasmidia (Secernentea)- 8 orders
• phasmids
• free-living or parasitic
• males with lateral tail extensions

2. Class Aphasmidia (Adenophorea)- 12 orders
• phasmids absent
• mostly free-living and few parasitic
• Males lack lateral tail extensions

Free-living Nematodes
Meloidogyne -root knot nematode Secernentea
Ascaris lumbricoides
Hookworms (Ancylostoma)
Incidence of Hookworm Disease
_ Unsanitary conditions: feces released into soil
– Repeated contamination of soil
– Repeated visit to same area to defecate increases transmission _ Environmental conditions: Warm and humid
– Must have loose, aerated soil, with lots of humus.
– Warm, humid climate necessary for the worm to develop in soil in shady areas
_ Exposure of skin to soil
– Must have access to skin so it can burrow into the skin.
Pinworm (Enterobius vermicularis)
_ Transmission: Eggs are infective stage. They are light and can float. 3 modes:
– Hand to mouth (fecal/oral contamination)
• Eggs are picked up on the fingers and transferred to mouth
– Inhalation
• Eggs float and are inhaled, trapped by mucus membrane, then swallowed
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