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Phylum Nematoda The Roundworms thread like www.onacd.ca Slide 2 Characteristics of Nematodes Level of Organization: Primitive Organ level Symmetry: Bilateral Complete ONE WAY digestive tube (separate mouth and anus!) Simple nervous system with a nerve cord on its stomach (ventral) Slide 3 Characteristics of Nematodes Developed reproductive systems Simple excretory system - excrete wastes through a pore Sexes are separate (males and females), sexual reproduction Cool fact: They are born with a certain number of cells that increase in size as they grow Nematode cysts found on corn Slide 4 Epidermis has a cuticle (made of collagen) to keep it from drying out Epidermis has a cuticle (made of collagen) to keep it from drying out Longitudinal muscles Longitudinal muscles Many parasitic and free-living forms found in soil Many parasitic and free-living forms found in soil Slide 5 Slide 6 Slide 7 Positive Roles of Free-living Nematodes They are decomposers: They recycle bacteria, fungi and decaying plants and animals back into the soil. Very important to energy recycling on earth! Slide 8 Negative Roles of Parasitic Nematodes Parasitic Nematodes: Invade many different types of crops can kill them Attack the bark of forest trees Invade the intestine of many mammals and cause sickness and death if untreated. Soybean Cyst nematode: infects soybean plant crops and causes cysts on the plants Slide 9 Parasitic Species of Nematodes include: WHIPWORMS - invade the human large intestine - responsible for Trichinosis HOOKWORMS - invade the small intestine of dogs, cats and humans - cause anemia as they suck blood ASCARIDS - invade the human intestine responsible for Ascariasis PINWORMS - invade the upper parts of the colon. FILARIDS - invade many different parts of the body and are responsible for many diseases (including elephantiasis and Loa Loa) Slide 10 Example: Ascaris lumbricoides Host infected accidentally by eating eggs in feces Worms live in the digestive tract, and eggs are released again in the feces Cool (gross?) fact: Upon autopsy, a 2 year old South African girl was found to have 796 worms in her intestine Slide 11 Slide 12 Example: Elephantiasis Nematodes are transmitted by mosquitoes They infect the lymph nodes Causes thickening of the skin and tissues