Phylum Nematoda Roundworms Examples Ascaris Large human roundworm

Phylum: Nematoda (Roundworms) Examples: Ascaris Large human roundworm Can cause pneumonia and intestinal blockage

Dirofliaria immitis • a parasitic nematode • that can kill your dog

– itchy butt worms Pinworm eggs

Larval stage forms calcified cysts in muscle of host ( human or pig/bear ) Trichinosis – contracted from undercooked infected pork

Filarial worms – transmitted by a fly or mosquito Live in host’s lymphatic vessels

Causes Elephantiasis

Causes River blindness

Causes blindness and skin lesions

Life cycle depends on a small “water flea” crustacean

Worm under skin

Characteristics • Unsegmented worms • Microscopic to a meter in length • Most are free living, some are parasitic • Pseudocoelom

Characteristics continue… • Have a digestive tract with 2 openings. (Mouth and anus) Now I can eat and poop at the same time! • Have specialized tissues and organ systems.

Specialized structures: 1. Simple nervous systems consisting of several ganglia. 2. Sense organs to detect chemicals given off by prey or hosts. 3. Thick cuticle made of chitin. 4. Some parasitic species have sharp toothlike plates and hooks to burrow into the skin.

Mode of nutrition: • Free living roundworms are predators. • Some soil dwelling and aquatic roundworms eat algae, fungi or pieces of decaying organisms. • Parasitic roundworms like Ascaris suck the host’s blood and absorb the host’s digested food.

Movement: • Use muscles to push their way through the ground or those in the water move like snakes. Reproduction: • Sexes are separate. • Sexual reproduction. • Roundworms have internal fertilization. • Parasitic roundworms have life cycles with 2 or 3 hosts.