MORPHOLOGIC STRUCTURES USED TO CLASSIFY NEMATODES
Mouth: External opening of buccal capsule sometimes with lips, ventral teeth or leaf crown.
Lips (Physaloptera) Leaf crown (Triodontophorus)
Ventral teeth (Ancylostoma) Ventral cutting plates (Necatur)
Lips: Fleshy lobes around the oral opening; prominent on ascarids which have 3 large lips.
Buccal capsule: Oral cavity that is absent in some superfamilies (Trichostrongyloidea) and large in others (Strongyloidea).
Subventral lancets: "Teeth-like" pointed structures projecting upward from the base of the buccal cavity.
Cephalic vesicle: Bulbous swelling of the cuticle at tip of the anterior end.
Cervical inflation: Inflation of the cuticle in the region of the anterior end of of the esophagus.
Transverse cervical groove. A cuticular groove that runs transversely as a posterior constriction the cervical inflation in the region of the esophagus.
Cervical papillae: Lateral barb-like structures in neck region.
Longitudinal cuticular striations: Rows of "railroad tie-like" markings on the cuticle running in rows down the length of the body.
Bursa: Two lateral fan-like flaps forming the posterior end of the worm and possessing finger-like rays or support structures. An "asymmetrical bursa" is one in which the dorsal lobe with its dorsal rays is located toward one side instead of in the center of the lateral bursal lobes.
Poorly developed bursa with blunt rays ( Metastrongylus)
Well developed, asymetrical bursa (Haemonchus)
Caudal alae: Cuticular flaps lateral to the cloaca that do not protrude beyond the tip of the tail. Caudal alae are often confused with bursa.
Spicules: Phenolic-colored chitinous structures that proturde through the cloaca of male nematodes and aid in copulation. Spicules usually occur in pairs that are even length or uneven and some species have only one.
Single spicule --- Trichuris
Long slender spicules fused at tip --- Nematodirus
Short, stout spicules --- Cooperia Trichostrongylus
Multiple terminal processes --- Ostertagia (left side)
Knobbed tip with lateral barb --- Haemonchus
Stichosome: Neck of nematodes in the Superfamily Trichuroidea that is made up of a single row of cells called stichocytes.
Stichosome (Trichinella) Stichocytes (Capillaria)
Diagram of Trichinella Whipworm (Trichuris)