The males die after mating. Gravid females migrate to the anus at night and crawl out onto the perianal skin. As they die and dehydrate the eggs are shot out by an ovijector. The second-stage larvae (L2) within the egg is infective within 12 hours of being ejected. When ingested by the rodent, as a contaminant on food or during grooming, the egg hatches and the L2 moves toward the caecum. Within about 4 days the larvae undergo 3 moults to the adult stage.

An unusual feature about the life cycle of this species, and several other pinworms, is the possibility for retroinfection. If the faeces are moving extremely slowly in the large intestine of the host, or if the host is constipated, the female worms may shed eggs while still in the animal. These eggs may have sufficient time to embryonate and hatch before being passed out of the host. If this happens, they can make their way to the caecum and mature in the usual manner. There is also evidence that eggs in the perianal region can hatch and the larvae enter the anus and migrate to the caecum.

You have both male and female worms in your slidebox. Structures to noteinclude the buccal cavity, nerve ring, esophagus and esophageal bulb, nerve ring, cervical alae, intestine and anus. On females note the uterus, ovary, vulva and ovijector and on males note the testis, ejaculatory duct, spicules and the mamelons.

Syphacia obvelata anterior end

Syphacia obvelata male posterior end

Syphacia obvelata male spicules

Syphacia obvelata female

Syphacia obvelata female posterior

Syphacia obvelata anterior