NEMATODA

Characteristics  Roundworms  Name means “thread- like”  Thought to be most abundant animals on Earth (only about 20,000 species identified, thought that there might be more than 1,000,000)  Bilateral symmetry  Size- all under 5mm

Anatomy  Long narrow bodies no legs  Pseudocoelomates  Mouth and Anus!  Excretion out of anus  Outer covering called cuticle is shed as worm grows usually 4 times during lifetime

Anatomy  No respiratory or circulatory systems  No skeleton  Two nerve cords  Has muscles

Feeding  Herbivores  Bacterivores  Fungivores  Predators  Omnivores  Parasites – picture is of Trichinella in pork meat

Trichinella spiralis  Found in pork meat that is undercooked  Symptoms – nausea, diarrhea, muscle pain as worms invade, cardiac problems, pneumonia, nervous disorders  No cure

Pinworms  Intestinal worms- live in rectum of humans  Female worms leave rectum at night to lay eggs on surrounding skin  Eggs can survive in bedding and clothing for 2 weeks  Spread by ingesting eggs  Medicines kill worms - curable

Ascaris lumbricoides  Intestinal roundworm  Female worm can produce up to 200,000 eggs a day  Eggs ingested from food contaminated with fecal matter  Larvae hatch, burrow through intestine, can migrate anywhere in body  Medicines kill worms - curable

Reproduction  Reproduce sexually  Both males and females  Usually males smaller in size than females

Habitat  Mostly found in soils  Can be found at bottom of deepest oceans to tops of highest mountains  Found in tropics to polar regions  Everywhere on Earth  Some free-living, some parasites  What are some biotic and abiotic factors?

Adaptations  Parasites are “wide- range” can infect many hosts  Nematodes have a metabolically- suppressed stage if survival is threatened  During drought they go into dormancy (like hibernation)