Morphology

There are three main features to a tapeworms external morphology: the strobila (proglottids) the scolex and the tegument. This post will deal with the strobila.

Strobila/Proglottids

• unique among the metazoa


• a linear series of sets of reproductive organs of both sexs - each is referred to as a genitalium


• the area around the genitalium is a proglottid


• tapeworms with mulitple proglottids are describes as being polyzoic
  
• new proglottids are continuously differentiated near the anterior end in a process called strobilation - as each segment moves from the anterior end to the posterior end a new one takes it place
• the new proglottids are produced in an undifferentiated zone between the scolex and the strobila, called the neck - this area contains stem cells which give rise to the new proglottids


• while the segments travel down the length of the worm they sexually mature, by the time they reach the end of the worm the genitalia have already copulated and produced eggs
  
• a proglottid can mate with itself, with others in the same worm or with another worm entirely (it depends on the species of tapeworm)


• a segment containing eggs is called a gravid


• when the gravid reaches the end of the worm, it detaches and passes out of the host in the host feces
  
• from here the eggs can be ingested by a new host, leading to tapeworm infection