|Worm-like and bilaterally symmetrical|
|An unsegmented body with claws at the anterior end|
|A porous chitinous epidermis moulted occasionally|
|4 chitinous hooks or claws at the head end|
|The larval stage has three pairs of leg-like appendages|
|A hydrostatic skeleton|
|A mouth, straight gut and anus|
|Striated circular and longitudinal muscles|
|A ventral nerve cord|
|Fertilisation is internal|
|Parasites of vertebrates|
|They don't have excretory, circulatory or gaseous exchange systems|
Greek: pente = five; stoma = mouth
Above is Lingutula serrata.
Pentastomida are the tongue worms. There are about 100 described species; all are parasitic, and range in length from 2 - 16 cm. Their main host is usually a reptile, where they live in the lungs and nasal passages (see Cephalobaena tetrapoda below). One species lives in the air sacs of terns, and another in the nasopharyngeal region of cats, dogs and just occasionally humans.
Many Pentastomida have an intermediate host which can be a fish, reptile or most commonly, small herbivorous mammals, e.g. rabbits. These intermediate hosts are then eaten by the primary host. Man can also be a host to the larval, or intermediate stage.
In the adult form there are usually five protuberances at the anterior end; four of these bear claws, and the fifth bears the mouth and two attachment hooks (see right). The adults live with the front (hooked) end deeply embedded in the host's tissue and feed off the blood, mucus or lymph.
The sexes are separate, and the female can produce millions of eggs increasing her size almost 100-fold. The eggs are swallowed by the host and then excreted with the faeces. The larvae have three, and later two, pairs of legs and a tail.