Introduction to the Cestodes
Adult Bodyplan
Cestode Tegument
Larval Metacercaria
Reproductive System
Infections of Man
Specific Cestodes
The Basic Body Plan of a Cestode
The study of the morphology of the cestode body may be divided into two distinct areas. Firstly the morphology of the adult cestode (the tapeworm) and secondly the morphology of the cestode larvae, or Metacestode.
The Adult Parasite
The body of the adult tapeworm may be divided into three region
i) The Scolex
The "head" and attachment organ of the parasiteThere are four main types of scolex, by which the tapeworm may be taxonomicaly classified.
a) No special attachment organs
The scolices of some tapeworms of the order Caryophyllidea* (parasites of freshwater fish) have no special attachment organs.
(* NB. Some authors do not recognise this taxonomic order, placing these parasites within the Pseudophyllidea)b) A Bothria
This is composed of a pair of shallow, elongated, weakly muscular grooves. Tapeworms of the order Pseudophyllidea are equipped with bothria on their scolices.
c) A Bothridia
Various artists
These are broad, leaflike muscular structure, exhibiting a large degree of variation. Some bothridia are sessile, some are stalked, whilst others are hooked with accessory suckers. Tapeworms of the order Tetraphyllidea and others are equipped with bothridia.
d) Acetabulate Suckers
Tapeworms of the order Cyclophyllidea are equipped with four acetabulate suckers. Parasites in this order may also have additional features at the apex of the scolex such as;
- Glandular areas
- Protrusible suckers
- Suckers armed with hooks
- Hooks (e.g. Taenia)
- A Rostellum, an eversible muscular proboscide, often covered with hooks (e.g. Hymenolepis, Echinococcus, Dipylidium)
- A Myzorhynchus (a protrusible muscular mass).ii) The Neck
This is the area of proliferation of the parasite, from which the proglottids of the strobila grow.
iii) The Strobila
This is composed of a series of proglottids
The proglottids each contain a complete set of male and female reproductive organs, although these organs usually mature at different rates. Usually the male organs develop before the female organs, and degenerate before the female organs mature. The large, gravid proglottids at the posterior end of the tapeworm are full of developing, or in the extreme terminal proglottids, mature eggs.
