Phyla Nematoda and Rotifera

• Pseudocoelomates
• lined on the inside by endoderm and outside by mesoderm
• fluid filled
• contains organs
• supports the body
• provides hydrostatic pressure against which muscles can contract
• serves as a storage area for wastes or eggs and sperm

Phylum Nematoda - Roundworms

· 10,000 - 80,000 (million) species

· long slender bodies that taper at both ends

· flexible protective cuticle

· digestive tract with two opening (1 way)

o anterior mouth

o posterior anus

· sexes distinct in most species (ie. guinea worm female = 120 cm; male = 2.5 cm)

· excretory wastes collected by system of tubes

o expelled through excretory pore in posterior end

· longitudinal muscles, lack circular muscle -> thrashing motion

· most free living

· many plant and animal parasites (enormous economic damage)

o humans host 50 species

o more than 1/3 of humans infected

· Ascaris

o found in the intestines of pigs, horses, and humans

o enter body in contaminated food or water ->hatch in intestines -> larvae bore into the blood stream ->carried to the lungs and throat ->coughed up, swallowed, returned to intestines -> mature and mate -> block intestines -> death

§ larvae in lungs cause respiratory illness

o females produce 200,000 eggs/day (contain 27 million eggs)

o shed through genital pore

o exit in hosts feces

Phylum Rotifera - Rotifers

• 1,750 species
• transparent, free swimming and microscopic
• freshwater and marine
• crown of cilia surrounding mouth
• cilia sweep food into mouth
• look like rotating wheel
• feed on unicellular algae, bacteria, and protozoa
• moves through pharynx -> mastax
• mastax (muscular organ) chops up food
• hydrostatic pressure inside pseudocoelom
• nervous system composed of anterior ganglia and two long longitudinal nerves
• two anterior eye spots