Phylum Nema toda The Roundworms “thread” “like”

Phylum NematodaThe Roundworms “thread” “like” www.onacd.ca

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 it’s stomach (ventral)

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

Epidermis has a cuticle (made of collagen) to keep it from drying out • Longitudinal muscles • Many parasitic and free-living forms found in soil

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!

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 voraciously PINWORMS - invade the upper parts of the colon. - Males are 1-4mm and females are 8-13 mm in length. FILARIDS - invade many different parts of the body are responsible for a range of diseases (incl. elephantiasis and Loa Loa) ASCARIDS - invade the human intestine – responsible Ascariasis

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

Example: Ascarislumbricoides • Host infected accidentally eating eggs in feces • Larvae hatch, burrow through the intestine, and reach the respiratory system • Cool (gross?) fact: Upon autopsy, a 2 year old South African girl was found to have 796 worms in her ileum

Life cycle of Ascaris lumbricoides • The larvae are then re-swallowed and mature in the intestine • Can be up to 30 cm in length • Larvae anchor themselves to the inside of the intestine • The worms grow and produce eggs • Eggs are released with the feces Ascaris larva developing inside egg Larvae exiting egg

Example: Elephantiasis • Nematodes are transmitted by mosquitoes • They infect the lymph nodes • Causes thickening of the skin and underlying tissues

Example: Trichinella • Raw or undercooked pork or wild game • Stomach acids and enzymes free the parasites • Enter the small intestine and travel all over the body (retina, myocardia, lymph nodes) and can complete their life cycle once in the skeletal muscle • Leads to gastrointestinal upset and oedemas • Serious infections may lead to strokes Picture of Trichinella cysts in pork (~1mm to 3 mm)

Life Cycle of Trichinella Mmm, now who wants to get some Pulled Pork Sandwiches! Or better yet, some pork chops!! 

Phylum Nema toda The Roundworms “thread” “like”