i) Adult hookworms have a slightly stout, cylindrical body with a curved anterior end, a dirty rust colour, and a tough cuticle. Male worms grow to be about 8-11 mm long, while female worms grow to be about 10-13 mm long.
ii) The anterior end has a large buccal capsule and is bent dorsally. This bend is parallel to the general curvature of the body.
Figure 1: Ancylostoma duodenale A. Adult female, B. Adult male, C. Anterior end, D. Posterior end of male
iii) The oral aperture is not terminal, but rather directed to the dorsal surface.
iv) The large and visible buccal capsule is lined with a hard substance and bears six teeth, four hook-like on the ventral surface and two knob-like on the dorsal surface.
v) The digestive system is controlled by five glands, one of which, the oesophageal gland, secretes a ferment that prevents blood from coagulating. A pair of amphidial or cephalic glands that reach backward nearly half the length of the worm are visible ventrolaterally in the buccal capsule. There is a single dorsal and two subventral digestive glands embedded in the oesophageal wall.
vi) The buccal capsule opens into the triradiate oesophagus, which is covered in cuticle. After a brief rectum, the oesophagus continues posteriorly as a straight intestine. In females, the anus serves as the subterminal opening to the rectum. However, in male, the rectum and ejaculatory duct enter posteriorly into the cloaca.
vii) A pair of thin cervical glands, also known as excretory glands, protrude through an excretory hole a short distance behind the head. A carrying cell, a suspensory cell, and a pair of tubules running from the buccal capsule to virtually the posterior end of the worm make up the excretory system.
viii) A circum-oesophageal nerve ring can be found just in front of the excretory pore. Back of the circum-oesophageal nerve ring are two lateral cervical papillae.
ix) Sexes are distinct from one another and can be identified by a variety of traits. The copulatory bursa is located at the posterior end of the male, which is smaller than the female. The hind end of the female is pointy.