Updated by: Arabinda Naik
General features:
Habit and habitat: They are commonly called nematodes. They are mostly free living and may occur in water or within the soil. There are several parasitic species which live within the body of animals or plants. Guinea worms, whipworms, eyeworms etc.
Symmetry: They show bilateral symmetry and have organ system level of organisation.
Germ layers: They are triploblastic animals and have tube within tube body plan.
Body wall: the body wall contains an outer cuticle, syncytial epidermis, and a muscle layer. Circular muscles are absent.
Body cavity: Aschelminthes are pseudocoelomates as the cavity present between the body wall and gut is not lined by mesodermal epithelium.
Digestive system: Alimentary canal is complete with well-developed muscular pharynx.
Excretory System: It consists of a pair of gland cells or intracellular canal or both.
Nervous System: It contains a nerve ring around the pharynx with dorsal and ventral longitudinal nerve cords running throughout length of the body.
Reproduction: Nematodes reproduce only by sexual method. Sexes are separate and exhibit sexual dimorphism. The male is smaller than the female.
Fertilization: It is internal. The fertilized eggs develop directly or indirectly through larvae that undergo moulting and finally grow into adults.