1. The Roundworms

2.  Triploblastic Pseudocoelomate  Three tissue layers  False Body Cavity No Mesentery (thin connective tissue) to support the organs) Fluid filled and acts as a hydrostatic skeleton, provides for circulation, aids in digestion

3.  Complete Digestive System (mouth to anus)  Most are microscopic  Bilateral Symmetry  Unsegmented  Most dioecious

4.  Epidermis is covered by an external cuticle that is often molted for growth

5.  Glandular in aquatic species  Tubular in parasitic species

6.  Cerebral ganglion- around the pharynx  Two longitudinal nerve cords

7.  Free living roundworms can be carnivorous or herbivorous, usually soil dwellers feeding on small or microscopic organisms  Parasitic roundworms feed off of their host tissues and fluids

8.  No circulatory system  Pseudocoel fluid serves to circulate some nutrients and wastes  No respiratory system  Gas exchange across skin-diffusion

9.  Dioecious  Often dimorphic  Males and females are different sizes  Method of reproduction varies by species

10.  Ascaris lumbricoides  Giant intestinal roundworm  Enterobious vermicularis  Human pinworm  Necator americanus  New world hookworm  Trichinella spiralis  Porkworm  Wuchereria sp.  Filarial worms (elephantiasis)  Dirofilaria immitis  Dog heartworm

11.  Rotifers-usually water dwellers  Gordian (horsehair) worms- live in running or standing water