Pseudocoelomates: Roundworms
Phylum Nematoda: very abundant in freshwater, marine water and sediments, soil; also parasitic in animals and plants; mostly in the millimeter scale, but up to 9 m (parasite of sperm whale placenta)
Pseudocoel: filled with water ? hydrostatic skeleton
Cuticule: thick, flexible layer on epidermis; molted 4 times in life
Muscles are longitudinal below epidermis, pull against cuticule and pseudocoel for movement
Trichinella: important parasite in pigs;human infection by raw pork meat