Phylum Nematoda The Roundworms

What are Nematodes? 80,000 species of roundworms are known There may be about 800,000 species that have yet to be identified! They are among the most numerous of all animals > 1 million roundworms present in one shovel load of soil . . .

Lifestyles of Nematodes Many nematodes are free-living Freshwater and marine environment Moist soil Parasitic forms Affecting BOTH plants and animals Troublesome in agricultural practice

“What do they look like?!?” ~ General Characteristics ~ Bilateral Symmetry Anterior / posterior Dorsal / ventral Cylindrical bodies Tapered at both ends Covered by tough cuticle Range in size < 1 mm extending up to > 1 meter

But what about the inside? Internal Structure of Nematodes Pseudocoelom … at last!!!! . . .but its fake!!! NOT completely lined with mesoderm They have a “tube-within-a-tube” structure

What about digestion? Simplest animals having a complete digestive system: Two separate openings One-way flow Digestive gland to aid in digestion

Definitely motile . . . Roundworms have a simple nervous system and well-developed muscles Muscle fibers located in body wall Move in whip-like fashion

The Success of Roundworms Specialized Reproductive System Separate sexes Internal fertilization within female Fertilized eggs have thick outer shell (free-living forms) some release juvenile larva(parasitic forms)

Internal Fertilization

Parasitic Roundworms Many harmful effects Agricultural Deformation of roots Health related Infection of other animals

Agricultural Parasites Roundworm damages plant cells Nematode can pierce through tissues Results in damage to roots Inhibits efficient root function Limits growth

Health Concerns 250 million people in the tropics are infected by roundworms of the group Filaria Results in conditions such as elephantiasis

Sanitation: an end to roundworms Many of the diseases caused by roundworms can be prevented through adequate sanitation practices Good personal hygiene Water treatment facilities Washing and proper cooking practices

Phylum Nematoda : looking back Major advancements include: The presence of a coelom But, remember . . . Pseudocoelom!! Complete digestive tract Separate mouth and anus Accessory digestive gland Reliance on sexual reproduction With internal fertilization Production of capsule around egg Release of larval stage