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Nematoda

Nematoda. The Roundworms. Basic Characteristics. Triploblastic Pseudocoelomate Three tissue layers False Body Cavity No Mesentery (thin connective tissue) to support the organs) Fluid filled and acts as a hydrostatic skeleton, provides for circulation, aids in digestion.

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Nematoda

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  1. Nematoda The Roundworms

  2. Basic Characteristics • TriploblasticPseudocoelomate • Three tissue layers • False Body Cavity • No Mesentery (thin connective tissue) to support the organs) • Fluid filled and acts as a hydrostatic skeleton, provides for circulation, aids in digestion

  3. Basic Characteristics (continued) • Complete Digestive System (mouth to anus) • Most are microscopic • Bilateral Symmetry • Unsegmented • Most dioecious

  4. Integumentary System • Epidermis is covered by an external cuticle that is often molted for growth

  5. Excretory System • Glandular in aquatic species • Tubular in parasitic species

  6. Nervous system • Cerebral ganglion-around the pharynx • Two longitudinal nerve cords

  7. Feeding and digestion • Free living roundworms can be carnivorous or herbivorous, usually soil dwellers feeding on small or microscopic organisms • Parasitic roundworms feed off of their host tissues and fluids

  8. Circulation and REspiration • No circulatory system • Pseudocoel fluid serves to circulate some nutrients and wastes • No respiratory system • Gas exchange across skin-diffusion

  9. Reproductive system • Dioecious • Often dimorphic • Males and females are different sizes • Method of reproduction varies by species

  10. Parasitic nematodes • Ascarislumbricoides • Giant intestinal roundworm • Enterobiousvermicularis • Human pinworm • Necatoramericanus • New world hookworm • Trichinellaspiralis • Porkworm • Wuchereria sp. • Filarial worms (elephantiasis) • Dirofilariaimmitis • Dog heartworm

  11. Other pseudocoelomates (aschelminths) • Rotifers-usually water dwellers • Gordian (horsehair) worms-live in running or standing water

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