Phylum: Nematoda Phylum: Nematoda

Nematodes Origin of the word nematoda: Nema = greek for thread Animals in this phylum include: A variety of free living and parasitic round worms Level of organization organ and organ systems Type of Body Cavity Pseudocoelomate Symmetry: Bilateral

Basic Nematode Body Plan Germ Layer: ecto, endo and mesoderm Body Plan - Tube within a tube Has 2 openings (mouth and anus) = complete digestive tract Pseudocoelomate Open cavity allows for: Organ development Allows nutrients to flow around the organs - Acts as a skeletal structure

Skeletal structure Hydrostatic skeleton: (Think: water balloon) Muscles act against the pressure of the fluid in the body cavity. Segmentation: Nonsegmented: outer body is smooth

Compare and contrast Platyhelminthes and nematodes share: Hermaphrodites Bilateral Significant evolutionary changes found Nematodes: Complete digestive tract (2 openings) Pseudocoelom (open body cavity)

Parasitic Nematodes Ascaris lumbricoides: Length: 20-35 cm (female is larger than male) Unlike other nematodes Ascaris worms are either male or female Host: Humans and pigs

Anatomy of Ascaris

Ascaris Life cycle Step in development Eggs are found in soil, feces or vegetation Eggs are ingested by host when host eats contaminated soil, feces or vegetation

Ascaris Life cycle Step in development Eggs are found in soil, feces or vegetation Eggs are ingested by host when host eats contaminated soil, feces or vegetation Once ingested egg reaches the small intestine it hatches. Juvenile worm moves into circulatory system

Ascaris Life cycle Step in development Eggs are found in soil, feces or vegetation Eggs are ingested by host when host eats contaminated soil, feces or vegetation Once ingested egg reaches the small intestine it hatches. Juvenile worm moves into circulatory system Once in circulatory system it moves to heart and then lungs Juvenile moves into lungs travels up the trachea up to the mouth.

Ascaris Life cycle Step in development Eggs are found in soil, feces or vegetation Eggs are ingested by host when host eats contaminated soil, feces or vegetation Once ingested egg reaches the small intestine it hatches. Juvenile worm moves into circulatory system Once in circulatory system it moves to heart and then lungs Juvenile moves into lungs travels up the trachea up to the mouth. Once in the mouth it is swallowed by host where it moves back down the esophagus past the stomach and back into the small intestine Once in the small intestine it feeds off hosts food and matures into a reproductive adult

Parasitic Nematodes Trichinella spiralis: Length: ~2mm Host: Human become infected when they eat undercooked pork. Pork muscle may contain encysted trichinella larvae.

Life cycle of trichinella 1) After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small intestine where they develop into adult worms. 2) The life span in the small bowel is about four weeks.

Life cycle of trichinella 1) After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small intestine where they develop into adult worms. 2) The life span in the small bowel is about four weeks. 3) After 1 week, the females release larvae that migrate to striated muscles where they encyst (form a cacoon-like structure) Diagnosis: Based on clinical symptoms, and is confirmed by serology (blood analysis) or identification of encysted or non-encysted larvae in biopsy or autopsy specimens.

Assignment Diagram the life cycle of Ascaris lumbricoides Finish vocab: 629-635