One of the largest nematodes known, females can reach the length of 800 mm while males may only be up to 40mm. Both sexes have a small, triangular mouth surrounded by a quadrangular, sclerotized plate but no lips.
Females have anterior and posterior branches to their uterus.
When gravid, the female intestine becomes squashed and nonfunctional. Some juveniles break out either through the body wall of the female or out through her esophagus. This produces an antigenic response in the host resulting in a large, painful blister which eventually bursts. The female protrudes from this opening to expel her young. This is done through contractions caused by exposure to cool water that force the J1 out in periodic bursts of up to 500,000 at one time.